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  #41  
Old 02-28-2010, 10:43 PM
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4.2.0.0 Welding The Receiver

Use clamps, vice grips and (nuts and bolts) to line up and place spot welds that will hold the receiver in form. Level all surfaces to the same plane and match all corners. If the corners or edges do not line up without distortion of shape, it means the receiver is warped. Spot welds should be placed in the following order.

Behind the magazine well
Front of the magazine well
Front End

IMPORTANT: if original style rear push-pin guides and reinforcement tab is to be installed refer to section 4.2.4.0 BEFORE spot welding the rear of the receiver.

I use TIG with very little filler rod and no copper backing used. This can be accomplished only if you are very good at the machine you are using, know its capabilities and potential. Less current will show the edges on the reverse, excessive heat will result in burn through. It is safer to use a backing to prevent burn through. Cheapest and most effective way to make backing is flattening common house hold copper pipes in a press between two solid surfaces, then contouring and shaping as needed.



Adequate penetration can be verified by examining the inside of the receiver. The welding I ended up with is a little too smooth; at some spots it will be hardly visible, especially after refinishing. All original HK welds are bold and visible.





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Old 02-28-2010, 10:43 PM
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4.2.1.0 Conforming the receiver to specification.

Now is a great time to check and fix all vital measurements. Almost everything may be out of specification at this point. Listed in the following sub chapters are solutions to problems that the receiver may have.

Below mentioned fixes exert a lot of force and stress on the receiver therefore they should be done only AFTER the receiver is fully welded.
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4.2.1.1 Receiver Rails

The rails are important for the Bolt Carrier (BC) to fit and slide inside the receiver freely but without any excessive play.

Too loose: If the bolt does fit the receiver and slides freely, rock it in the opposite direction (side to side) to determine excessive play. If it does have excessive play, it will most likely be corrected automatically when checking for the Trigger housing opening as done in next sub chapter 4.2.1.2.

Just right: Distance between the Rails on factory guns are .8900” / 22.6mm. If the bolt slides freely, simply skip ahead to the next segment regardless of this measurement.

Tight / Will not fit: It is common that the rails end up being too close together, which does not allow the bolt to be inserted (or it is too tight, where it does not slide freely simply by tilting the receiver back and forth). In this event, bolt carrier itself can be used as a mandrill. No, you cannot hurt it or wear it out, especially the .308 Bolt carriers (BC).

I keep a dedicated BC as a mandrill. Strip the carrier before this is done. Remove bolt head, locking piece, firing pin and spring. Use a 5/32” punch to get the bolt head locking lever pin knocked out and remove the bolt head locking lever and spring – Now the BC is stripped.

Insert the BC from either side; with the trunion not yet installed it makes no difference. Do not use a hammer or a mallet as that will damage or marr the receiver. Use a press to press/push and make certain that the receiver surface make even contact on the resting surface so it does not get egged or bulged.



It is not likely that the rails are pulled apart sufficiently due to the fact that the receiver has spring action around the rails. Therefore I used shims which are cut as needed (shown below). Material for the shims can be obtained easily as described in the first picture of section 4.2.0.0.

Each time the carrier (with or without shims) is pulled/pushed through, it will make a difference. Run the same setup three times before increasing / adding the shims.



It is not necessary that the area of resistance will be the rails alone. Below you can see how I place a shim on the BC to loosen the curved side walls as well. Keep in mind that these shims can be added as needed.



By now most issues are solved and the BC should run free and clear. In the unlikely event that the BC still has issues the following method may be applied.

Note where the BC is sticking, and press the BC to that area (use a press if need be). The BC should be places around the spot where the obstruction is, that means the bolt should extend either side of the spot. Shims need to be used if they were used previously. Hold the top of the receiver in a round backing as to not flatten in, heavy barrel vice clamps work great for the job (wood can also be tried). Press the BC slowly and check for clearance (with the shims out, each time – I know this is a little work) often.

You really have to be an expert for this procedure as it is very easy to create defects which cannot be corrected. Use a 12T press so the press can be felt as one progresses.




There is more on this topic in sections 6.1.0.0 and 6.2.0.0.
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4.2.1.2 Lower Opening

Here I fit the lower Housing to the receiver and make it fit tight and snug. It should not be loose as that will result in a wobble. Before I start on this, I have already completed section 4.2.4.0 or decide to leave the rear as is but still welded completely.

Lower Receiver Opening – Should be about 0.9120” wide measured from the outside. It is same as the Sear Pack box (inside the housing).
The receiver is squished with the help of a regular vice. Wood or cloth may be used to prevent marring. It is vital that the Bolt carrier / mandrill be used when squishing the receiver (as shown below) so the rails are not disturbed. It shims were used with the BC, they need to be used now again. Do not over squish, check by trying to install the lower till it fits.

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4.2.1.3 Trigger Housing fit

With the lower opening set there is one last step to do to get the Trigger Housing to fit correctly. First I try and fit the lower (with the sear pack housing inside) and measure the gap that is left between the upper edge of the housing and the receiver line. This is the measurement by which the tabs on the receiver must be reduced / shaved off.

On my receiver, the tabs need to be trimmed for almost 0.1200”
(the lower has the sear pack housing inside, that is what prevents proper seating as the receiver tabs as too long)



After the tabs are trimmed, the lower (with the sear pack housing - cage inside) fits nice and snug. Push-Pin hole alignment is very good. After the pins are inserted, there is no play back or forth. In case the holes do not align (vertically), please refer to section 4.2.1.5.



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4.2.1.4 Magazine Well

Magazine Well – Should be 1.1500” / 29.2mm wide. Best way to check fit is to insert a magazine. The walls are bent, preventing the magazine from being inserted. In-fact the edges are so sharp they tend to shave the magazine.

To straighten out the lip do not use a players or similar tools, they will distort the edge which looks very ugly. Instead use a backing plate that can only catch the lip and not the bulged reinforcing stamping.



Press both side by placing a solid flat surface on the outside that runs through. The support on the inside (where the ram presses) can be smaller than the Magazine well, just move it around back and forth.



Now the magazine fits perfectly, without any wobble. It is held tightly and securely.

Next I inserted the BC group (while firmly pushing in the magazine with one hand) and noticed that the Bolt Head barely touches the Magazine Follower but clears both sides of the feeding lips – This is perfect.

To correct magazine depth into the receiver, apply procedures mentioned in section 4.2.1.1 and 4.3.2.2.

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Old 02-28-2010, 10:45 PM
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4.2.1.5 Stock / Back Plate Mounting

Attach the lower trigger housing and try to fit the rear stock (Back Plate Mounting) on. Most likely it will be very hard, use a mallet. Receiver height measurement at rear end – About 2.6400” high. This height can be adjusted by either pinching the receiver or by squishing it as described in sections 4.2.1.1 and 4.2.1.2.

If the Back Plate is mounted and holes do not line up, they can be adjusted. Hole can get misaligned because of procedures that were followed in section 4.2.1.2, but they will not be off by much. In the picture below you can see that three holes are fine but the fourth is off by 1.5-2mm.



The misalignment can be easily corrected by running a smaller diameter rod (which will barely fit) through the holes and press them into alignment. Correcting a 1.5-2 mm alignment issue does not distort anything out of specification that will impact other functions.



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4.2.2.0 Magazine Catch

Notes: It is important to understand the relationship between parts before any adjustments are made. Top lip edge on the magazine anchors on the magazine catch, locking in the magazine at a specific depth into the receiver. Magazine catch rests on the lower edge of the magazine catch window of the receiver. Excessive trimming of the lower lip of the magazine catch window (of the receiver) will move the catch lower, resulting in the magazine locking lower in the receiver.

At this point the magazine catch holes are undersize, that do not accept the parts. The catch window itself needs work to accept and seat the catch properly.

Both holes for the Magazine Catch are under size. Enlarge left hole with a 6mm / .2360” drill. Enlarge the right hole with 5/16” bit as it also accommodates the contact piece (which goes over the Magazine catch arm).



After I inserted the magazine into the magazine well, I take note of the locking edge on the magazine lining up with the upper edge (of the catch window on the receiver) perfectly.



I tried fitting the magazine catch but the receiver prevents it from proper seating. Trace a precise outline and trim, being very-very precise on the lower edge of the window.



Still does not fit, needed just a bit more shaving. I used a hand file as I really wanted to go slow till I got it to seat. I don’t want to rebuild this surface using a welder.



Now I fit all pieces and make certain all is functioning well. Also insert a magazine and notice how it seats and locks.

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4.2.3.0 Welding the Semi-Auto Wedge (Shelf).

As I have set the shelf on the Trigger pack housing to factory specs, the simpler way was to place the receiver wedge at factory specs too.

The factory wedge on the receiver is set at 1.4200” (X – shown in the picture below). Referring back to section 3.7.2.0 and 3.7.3.0; the grip frame measures 1.3880” / 35.25mm, this difference exists for the compensation and contour of the receiver.





Now that I know that the shelf needs to be at 1.42” below the receiver designated line, I prep up the shelf and measure both sides to be symmetrical (this also levels out the shelf).



I weld the bottom heavily. I weld the remaining edges lightly. Make certain that the welds are not obstructing the path or the surface while engaging the Trigger Housing.



Now I decrease the width of the shelf to match the trigger housing (also see section 3.7.4.0).

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4.2.4.0 Welding rear Push-Pin support and sleeves.

This plate (spacer) is offered in new by Blackwing on MilitaryFirearms.com HERE.

Some builders simply weld the bare receiver and that works well for them. Below steps are not required for the gun to work. Here is what a simple receiver weld looks like. It works well by simply pushing pins in after installing the lower Trigger group housing and the butt stock end cap.



Although they are not required, they are surely desired. I start by enlarging the pin holes to .400” Then I place the demilled reinforcement plate (see section 2.6.0.0) with push pins inside the receiver and secure in place using a clamp.

As long as the outer receiver surface levels with the push pins, I am in specification to fit the lower Trigger pack housing.



After welding to match the factory, I clean the welds off and grind flush the bottom outer surface. In case the holes do not line up with the Butt Stock end plate refer to section 4.2.1.5. In the picture below the bottom needs a little more grinding to be flush plain.

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Old 02-28-2010, 10:46 PM
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4.3.0.0 Welding / Installing the Trunion (barrel), Charging Tube and Rear Sight

There is a unique relationship between the Trunion (that has the barrel and Front sight), Charging Tube and Rear Sight. Before I weld up any part, I mock up and check for fit and correct alignment.



4.3.0.1 Preparing the Trunion

Clean the Trunion for any oils and grease. I use liquid Tide laundry detergent. Degreasing facilitate good welds.



Buff out any material left over from the spot welds on the trunion that may obstruct the trunion from being inserted smoothly. Do not over clean or polish Trunion surface as that may decrease the size, which may result as a wobble or play when inserted into the receiver before welding.

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4.3.0.2 Preparing Charging Tube

Bevel the inside of the cocking tube as shown in the picture below. The edge should be round and not marred. This beveling will allow bolt carrier a smooth ride when in battery (if the reinforcement is not full length). Also bevel the edge where it will mate with the receiver for welding.

The edge should be perfectly round so it may mate with the receiver without any gaps.

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4.3.0.3 Preparing Rear Sight

Mount all parts on to the RSB and locate a neutral setting. This means that I dial the windage and elevation to the very center of their higher and lower limits.

Elevation: The drum has a total of about 10 revolutions (360 degrees) that can be effectively used before the drum becomes too loose. Tighten the drum all the way and then loosen full five circles, this will allow equal amount of adjustment up or down. Special tool is needed for elevation adjustment. Fine needle nose pliers also work.



Windage: The windage screw has a total of only 5.5 full revolutions. After tightening it completely, loosen 2.75 circles (1 circle = 360 deg). This will allow equal adjustment, whether left or right. It is also easy to tell visually when the sight is centered on the base.



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4.3.0.4 Setting up the Boresighter

This will be used later in lining up sights. Ideally use a boresighter that can be chambered (less chances of errors). Below I use a cheap NcStar, it is the type that fits on to the muzzle.

There are a lot of methods to make a muzzle laser boresighter accurate. If it is round, roll freely on a flat surface (after turning it on) like a flat table top and notice the dot projection on the wall, the dot should not wobble vertically. The dot projected should be traveling in a straight horizontal line and not up and down. If the spot travels vertically, the boresighter needs adjustment.

I held mine in a drill press and marked a reference point on the floor. I made adjustments till the dot projected did not wobble upon rotating in the drill press.

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4.3.1.0 Drilling Holes in receiver for trunion

I locate all four holes on the receiver exactly where the original spot welds were (as done in section 2.3.0.0). If the trunion surface is inadequate due to de-milling or cleaning off the spot welds (and repair is not possible), the holes must be relocated to get a nice weld. But if the welder has good skills, the original location can be rebuilt at the same time as welding and thereby maintaining original location. Some builders weld at three locations on each side for a total of six, I find that overkill.

All four holes are centered .25” from the front edge (the front band on the Trunion is only .5” wide).

Top holes: Locate spots 1.4” apart, keeping the top of the receiver in center.



Bottom holes: Locate spots about .6” apart, keeping the bottom weld in the center.



Drill all four spots with a ” drill bit; this size will replicate the original welds in diameter. Deburr the surfaces which will ensure a smooth insertion of the trunion.

Top holes came out good.



Bottom holes should have been about 1mm more towards the edge but the drill walked. This situation is not aesthetically desired but is still within limits. On the second hole, the drill slipped and ate the edge. As visible, I had to rebuild the whole edge solid by welding and re-carve the edge.

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4.3.2.0 Mocking-up Trunion and Charging Tube in Receiver

Here I use various methods to determine the ideal location for parts to match up. All steps are not mandatory, but I am not trying to spare any effort. I want this rifle to be accurate enough for hunting and target practice. Upon using premium loads, I want it to perform at an acceptable level that is expected with quality 7.62X51. If I were to spare details and effort, CAI $600 rifles would have been less work and far cheaper.

I start by inserting the Charging Tube into the Front Sight (triple frame). Then insert the other end and Trunion into the receiver at the same time.



Notice how the first edge rests on the Trunion.



If need be use a mallet simultaneously on the charging handle and the trunion to set into the receiver, as indicated by the arrows. I used a small plastic screwdriver handle through the front sight post to set the charging tube.



The trunion and charging tube should go in fairly easy with a mallet if receiver welds and Trunion were properly cleaned. Once in, the Trunion and Charging tube will be seated flush with the receiver.

Excessive gaps between the trunion and the receiver can be corrected by pinching the front of the receiver as shown in the next step 4.3.2.2.



Now match up the index on front sight post and the charging tube (as prepared in section 2.2.0.0).



The Charging tube will not be resting on the barrel. There should be a gap left between the barrel and the charging tube. More on this later, when I get to weld the charging tube in section 4.3.5.0.

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4.3.2.1 Boresighting

Step 01 – Clamp the rifle (with the Trunion and charging tube pushed in) on a table or in a vice. It is imperative the rifle is straight (not tilted to either side). Should the rifle be tilted, we will end up with a canted sight. Pitched up or down does not matter i.e. vertical variations (up or down) do not matter. I use a regular water level to make certain the rifle will not be canted to either side. Reverse sides on the level to check for variances.



Step 02 – Rifle needs to be held firmly in place, but do not over tighten to the point that the receiver/Mag well is distorted or squished and not allow magazine to be inserted. Once things get welded, it will be very hard to tweak the receiver.

Pin up a sheet of paper opposite the muzzle. The distance really does not matter but it should not be too short. I have it at about 12 feet from the muzzle, we will be going by line of sight – not trajectory



Step 03 – Look through the barrel and make out the center spot on the paper through the barrel. Now mark a dot on the paper target that falls dead center when looking through the bore. This is visual Boresighting.



Below I mimic a misaligned trunion/barrel by not properly seating them to illustrate a point.

It does not take an expert to tell if the receiver is lined up straight when looking through the bore. In the picture below, it is clear that the receiver is NOT lined up correctly. With the bore centered in my vision, the rails do not appear equal. Clearly I need to adjust the barrel to the right so the rails will visually appear equal when I look through the bore. I made this correction in the next section 4.3.2.2.



Step 04 – Install the boresighter and turn it on. Rotate the boresighter in the muzzle and the projection should not move (also it should relatively be the same as the mark #1 already placed). If the projection moves, it will be in a circle around the mark that is already placed in the last step. Should the laser not be exactly centered on the mark, just take the center of the circle the laser makes itself or try fixing the laser (as explained in 4.3.0.4) but there is not a whole lot one can do if the arbor itself is kaput.



I use a level to draw a (true) vertical line through the first mark (from visual/bore sight). Now I place a SECOND mark (on the line - above the first mark) to compensate for the distance between center of bore and front sight blade notch. Place mark # 2 exactly 2.1010” above the boresighter dot. [0.4295” (0.8590/2 half of the barrel and part of FSB measurement) + 1.6715 (distance from the base of the FSP over the barrel to the tip of the blade)]



Now I have a verified line of sight for setting my rear sight. All I have to do is line up my rear sight assembly (complete) with the front sight and to the Dot # 2 on the wall. This determines the precise location at which the RSB will be welded. Verify the location again by turning on the boresighter and check that the beam is still set at dot #1while sights line up to dot #2.
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4.3.2.2 Fixing Canted/Misaligned Barrels

Here I will list some procedures that can be used to correct the trunion and receiver fit. They can also correct slight gaps that may exist between the trunion and the receiver.

Trunion has raised surfaces where rails should rest flush.



Both rails should be in contact with the Trunion evenly when properly installed.



Reasons for the rails not resting on the trunion evenly are limited. No, it’s NOT the flat that is defective or designed/manufactured incorrectly! Rails can get uneven if mandrill was not evenly placed when squaring rails. Using undersize rod through the receiver when folding can lead to receiver to be uneven. This will leave small variations that cannot be corrected regardless of the use of clamps to level surfaces and match ends when welding (section 4.2.0.0).

Fix # 1 At this point, very slight adjustments can be made to correct misaligned Trunion (barrel) fit with the receiver. Use a press to apply force at the base of the barrel / edge of the receiver. The receiver and the barrel must be well supported so they do not bend or warp. The force should only affect the front end of the receiver that contains the trunion, forward of the rails. Shims can be used to support the barrel profile.

Use a solid rod instead of the charging tube. You don’t want the charging tube dinged up. My illustration in the picture below does not support the barrel and receiver as good as I have suggested above. If you do use this procedure, make certain they are supported well.

Excessive force will disfigure the receiver opening, ruining it. Well the rifle is ruined anyways because of the canted barrel if only iron sights are to be used. However the rifle can still be usable (if the barrel misalignment does not bother you) as long as target is acquired via mounted optics or a simple barrel mounted laser (boresighted at varying lengths) lol. This method can also be used to fix misalignments mentioned in section 4.3.2.1.



Fix # 2 The front end of the receiver can be pinched in using rods (punch shaft, screw shaft, bolt shafts and drills all work) that are small enough to fit into the groove. Receiver front end must be supported by the bolt carrier or the trunion (with a support like a solid rod for the bolt guide) itself. I placed the contraption is a vice and tighten away.

This procedure is highly recommended to eliminate any gaps that may exist between trunion and receiver when mocked up. It does correct alignments also but not as effectively as the one above. The smaller you keep the pinching rods, sharper the pinch. The supporting rod I use for the bolt guide has a tight fit, so I don’t have to worry about the charging tube extension not fitting.



In the picture below, I use the bolt carrier itself. Here one has to be careful as to not over pinch which may result in the guide tube extension not fitting. Also notice the use of drill buts instead of larger rods for pinching.



Now install the Trunion (barrel) and the charging tube back into the receiver as done in section 4.3.2.0. Things may fit a bit tighter, but that is expected. Repeat section 4.3.2.1.

Once everything is lined up, it is a good idea to insert the bolt carrier and see if it fits. With all the stress applied on the receiver, it is easy to get it out of specification. Should that be the case, refer back to section 4.2.1.1. and repeat section 4.3.2.1.

Now that everything fits and lines up, clamp the receiver and the trunion as it is easy for this setting to change with everything else going on. Locate the clamp where it grips the rear ring of the trunion, this keeps the front clear for welding (placing it in the center will dent the unsupported receiver). I keep the clamp in place till I at least place two welds later on in section 4.3.4.0.

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4.3.2.3 Trunion and the Rails

The inner surface of the trunion should be flush with the rails so the rollers on the bolt head can transition smoothly. If the inner surface of the rails (that contact the rollers) do not line up with the trunion, refer to section 6.2.0.0.

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4.3.2.4 Rear Sight

This rifle has a long sight radius, making correct placement of the rear sight very important. Unless one settles for some after-market stuff, there is not a whole lot that can be accomplished with the standard Front Sight blade (I guess one can always file down the post to lower elevation lol). The rear sight is solely responsible for windage and elevation. It only makes sense to determine placement of Rear Sight Base (RSB) with the utmost care and precision.

I place the rear edge of the RSB (complete assembly) at 1.39” from the back end of the receiver. Now I line up the sights to mark # 2 on the wall. This is the location for welding the rear sight base. Mark accurately and carefully with a scribe.



As it happened in this case, I had the front sight canted to the left about ” at about 12 feet. One can only imagine the variance this could have caused at say 100 yards if gone uncorrected. The trunion had to be indexed correctly in the receiver.

Before making any corrections, it is important to understand what exactly needs fixing. If there is a cant, it can simply be the rear sight or the trunion not indexed correctly when pushed into the receiver. Refer to last section 4.3.2.2 for detailed fixes.

Here is another alignment test that can be done. Run a thread over the Front sight notch and straight to the center of the receiver at the rear (or the notch in the rear sight). The thread will let you know if there are any alignment issues.

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Old 02-28-2010, 10:49 PM
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4.3.3.0 Welding the Rear Sight Base

Now that I have the rifle boresighted and still held in the vice, it is a great time to weld the RSB. I do not bother to strip the drum from the base, which may move the exact location. Hold in place (as determined in section 4.3.2.3) using vice grips or clamps. Do not over tighten the clamps/vice grips as that will dent the receiver.



Weld the front end of the base first. This will not allow the site to shift when we get to the sides.



With both the sides also welded, the RSB is installed.



These welds came out larger than I wanted because the welder was hotter than I would have liked, resulting in a larger puddle. Grinding, buffing and going over again with a welder without any filler will smooth it out.
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Old 02-28-2010, 10:49 PM
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4.3.4.0 Welding Trunion

Here are Mark Graham's (ARS) notes.

I boresighted again, just in case. Here I used a MIG welder. I started welding on the lower holes and kept the “puddle” on the trunion, then slowly work towards the edge (in a circular motion) of the receiver while feeding filler. This ensures a strong bond. This is repeated for the remaining three holes.



Next I weld both sides where rails meet the trunion. Welding on the upper edge is sufficient.

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Old 02-28-2010, 10:49 PM
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4.3.4.1 Drilling Barrel Retaining Pin Holes and Chamfer Receiver Edge

Flats do not have the barrel retaining pin hole drilled like the original (or the PTR for that matter) receiver. These holes are not required, but are done only to conform to the original. These holes will come in handy should one need to change out barrels, which is an unlikely and unfortunate event.

Holes could have been drilled before welding the trunion. That would have allowed repeated insertion of the trunion to check for location and shape. however the labor involved will be no less.

Front edge of the receiver is rather sharp, so chamfering it is also in order.



Drilling the holes.

The holes are on a curves surface therefor are not round, they are elongated. Here is a pic of the demilled receiver stub straightened out.



Ideally one can use a endmill on a knee mill. But not knowing exact/precise measurements (center line) creates a possibility of milling into the trunion. I use an undersize drill and locate an edge on the trunion for both sides. My pilot holes are 33.5mm apart. They are 8mm from the edge. They fall in line with the top of the magazine well line as indicated.



Using a burr I match the receiver hole to the trunion hole for the pin on both sides.

PIC

Chamfering the edge

I used a small wheel (2") bench grinder to get a sharp angle. finished off the touch-up with a hand file. Only worry here is grinding off too much and then having to match the rest to it. I recommend supporting it on a rest when using the grinder.

If you are patient, a hand file alone can produce excellent results without the risk of accidents on the grinders or dremel.

PIC
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Old 02-28-2010, 10:50 PM
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4.3.5.0 Welding Charging Tube

Here are Mark Graham's (ARS) notes, also refer back to section 4.3.2.0 to refresh settings.

There should be no gap between the Charging Tube and the roof of the receiver. If there is a gap, the bolt will not ride smoothly and possibly jam (especially if the extension is cut short).

The front end should be well centered in the Front Sight Frame (triple frame).



Again check to make certain the tube is indexed correctly (as in section 2.2.0.0). The horizontal depth should also be adjusted by matching the tape to the frame. I held it in place using some Velcro and cardboard as shown.



Welding a tube / pipe requires additional skill. Fortunately the class I took (back in the day) was sponsored by Chevron and they went heavy on pipes of all size. HK Factory welding along the tube is done in three passes, so setup accordingly where your body can be most stable.

On hindsight I should have used TIG to mimic the original style but I had the MIG all set up. The weld in the first pic needs a whole lot cleaning and buffing.

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Old 02-28-2010, 10:50 PM
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5.0.0.0 Installing a paddle magazine release.

Quote:
CA Residents can undertake this project and still comply with the law by simply removing the Contact Piece and installing a longer spring. Or a spare contact piece can be baught and the notch removed (or simply use a bushing instead) as done on the Factory HK Semi-Autos. Bear in mind you will still need to use Magazine Release Locking Device for disabling the push pin.
Again, this procedure is totally optional. Here I install a magazine release lever (aka paddle mag release. aka flapper) as present on the original guns. Here is a very good thread on HKPro for this process. This thread was my inspiration. I did make some changes to the bushing and axis pin as explained below.

Here are the notes from Mark Graham's sight (ARS)

Mechanics. When the lever is actuated it slides the Contact Piece located on the shaft (inside the receiver, next to the spring) of the magazine catch, having the same result as the button being pressed to release magazine.



Parts

Lever. You can choose to upgrade your Mag Release lever to an Anti-Rattle one - Highly desirable.

Bushing and Axis Pin. Holes drilled in the receiver cannot be 6mm or larger as they will enable the unmodified lower to be attached, violating NFA (ATF) regulations. I use the original bushing and push pin shaft as busing (the original bushing and the push pin were cut to the same width as the lever). I use a 11/64" drill as the axis pin (just because it was handy, anything else can also be used as long as it is not smaller than the hole in the push pin, to avoid excessive play).

The 11/64" drill does not readily fit inside the push pin, so I used the very drill 11/64" to enlarge the push pin. I keep the drill intact as of yet, because I have yet to drill holes in the receiver.

I could have gone with the alternate bushing and axis pin as listed below, because of my decision I am feeling cheap! But i guarantee my contraption is just as durable, strong and functional as the alternate.

Bushing and Axis Pin Alternate. One can always use a solid one piece bushing (same size as the original bushing) that has a hole smaller than 6mm. Then match the axis pin to the hole. This cuts down on the number of parts used. No pic for this.

Remove the wire spring before drilling the pin. Discard the thin part of the original bushing. Cut the pin and the bushing as wide as the lever as shown. Do not cut the drill to get the axis pin yet as this same drill will be used to drill the receiver.



It is easier to do this procedure on guns built from flat as compared to factory HK because the factory have the Semi-Auto shelf passing right through the area where the release goes. If you have a factory gun, you will have to get creative and mill out the shelf portion inside completely. A tool like Dremel with assorted burrs work well for this.



Location and Drilling


PIC

Parts instillation


PIC

Welding



PIC
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Old 02-28-2010, 10:50 PM
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6.0.0.0 Issues.

With all the building complete, most likely we still do not have a functioning rifle - This is common. Parts will still need finer tweaking to run smoothly. Most fixes listed in Section 4.2.1.0 and its subsections (4.2.1.1, and 4.2.1.2) are now not practical, however some still may be useful.

Below I go over some that are very common.
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Old 02-28-2010, 10:51 PM
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6.1.0.0 Bolt Carrier
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6.2.0.0 Rails and Trunion

Rails should line up as shown in section 4.3.2.3. If the rails do not line up flush, it was most likely caused when the rails were straightened.

Below are some methods that may be used to line the rails.
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Old 02-28-2010, 10:51 PM
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6.3.0.0 Hand Guard Fit

Handguard fitting solely relies on the distance between the trunion and the hanger where hand-guard retaining pin goes.

This fitting should be fine because, I have not changed the factory settings. Criteria listed below can affect the distance between the trunion and the hangar.

1. - Barrel was not pushed out of the trunion.
2. - Front sight post has not moved on the barrel.
3. - Charging tube (where the hanger is located) has the same depth as before into the Front Sight Post.
4. - Hangar itself is at the same location on the charging tube.

However, in the unlikely event a handguard does not want to fit here are some solutions.

Too Tight


Loose



6.3.1.0 Correcting Charging Tube location

Front handguard mounting can be an issue if the charging tube is not installed or welded correctly.
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Old 02-28-2010, 10:52 PM
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7.0.0.0 Refinishing of Metal

I have decided to do paint over parkerizing.


Sand/ Media Blasting



Parkerizing



Painting
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Old 02-28-2010, 10:52 PM
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8.0.0.0 Refinishing of Wood

I will be going with the wood furniture. Forearm and the butt stock will be wood and the pistol grip domestic made black plastic. Refer to section 1.7.0.0 to determine your build compliance with 922(r). Refer to section 6.3.0.0 for issues with fitting hand-guard.

Obtaining wood furniture is fairly easy and cheap, about $20-25. There is a difference in style when it comes to CETME and H&K. Size are pretty much the same, they should interchange with minimal effort. Here are some sites off my head that carry them.

http://www.robertrtg.com/g3woodbuttstock.html

http://www.centerfiresystems.com/HK8941.aspx
http://www.centerfiresystems.com/han...arthk8951.aspx
http://www.centerfiresystems.com/g3w...arthk8948.aspx

With a little patience one can obtain US made wood butt stock and hand guard, although it gets to be a little expensive. Expect to spend about $100-150 for the butt stock and forearm EACH! Below are some links that I know off, I am sure there are others.

This guy made his own grip.

Here - US made wood grips.
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Old 02-28-2010, 10:52 PM
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9.0.0.0 Range Report and final notes
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Old 02-28-2010, 10:53 PM
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Here are some great Answers to Questions you may have
Get answers to CETME and G3 compatibality also.


http://www.robertrtg.com/g3qa.html



Bending a flat Video on YouTube. Don’t exactly like this mandril. I prefer to square up the rails as we did before bending the flat.





HKPro Special Topics



Bolt Gap





Bolt carrier, Bolt head and Locking lever Instructions

http://www.militaryfirearm.com/Forum...25&postcount=1



ARS Notes

http://www.arizonaresponsesystems.co...r91build.shtml



Very good video for functioning action in battery starting at 28 seconds.





Links to some builds

http://www.pirate4x4.com/forum/showthread.php?t=688219

http://uzi-world.net/forums/showthread.php?t=31109

http://www.falfiles.com/forums/showt...hreadid=106235
.http://www.falfiles.com/forums/showt...hreadid=109042
..http://www.falfiles.com/forums/showt...hreadid=124877

http://www.weaponeer.net/forum/forum...?TID=5794&PN=1
.http://www.weaponeer.net/forum/forum...?TID=5452&PN=1
..http://www.weaponeer.net/forum/forum...?TID=7441&PN=1
...http://www.weaponeer.net/forum/forum...?TID=7442&PN=1
....http://www.weaponeer.net/forum/forum...?TID=7443&PN=1

http://www.smcomp.com/~smurph/G3-build.html

http://www.weaponeer.net/forum/forum...232&PN=0&TPN=1

http://www.smcomp.com/~smurph/G3-build.html



Short Clips from AGI Tutorials. Not the complete thing ..

AGI Video Armorer’s Course trailer on You Tube!!





AGI Video G3 Building trailer on YouTube !! Its not exactly what we want as they don’t build from a flat. They also spend a lot of time on other types of receivers.

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Old 02-28-2010, 10:55 PM
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Here are some pics and videos for you to enjoy!










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http://www.youtube.com/watch?v=HACgSx2DISA
http://www.youtube.com/watch?v=AwaBB_INX24

All their facts in the following video may not be readily accepted by all.
http://www.youtube.com/watch?v=QCkFGluzfd8
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Old 03-01-2010, 7:40 AM
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Some one has been a busy busy boy! Nice job Time to sticky this thread
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Old 03-01-2010, 8:28 AM
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Quote:
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Some one has been a busy busy boy! Nice job Time to sticky this thread

Hey Woody - I have yet to blast and park this beast. Tanks ready ??
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Old 03-01-2010, 8:47 AM
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Quote:
Originally Posted by fredieusa View Post
Hey Woody - I have yet to blast and park this beast. Tanks ready ??
It's good to go!I'm ready when you are
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Old 03-01-2010, 12:34 PM
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Great job fredieusa. This may be the very best HK thread I have ever read. Keep up the good work.
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Old 03-01-2010, 1:53 PM
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Awesome write up so far!
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