mp5 build

[valley82]

They don't cut the releif into the jig because the same jig is used for 91, 93 and mp5 flats, each has a different spot that needs to be cut so that the flat will bend correctly.

[generalpetres]

How much do you think i should remove from the jig bar?

[ar15barrels]

How much do you think i should remove from the jig bar?

None.

[valley82]

When building a 91 you have to remove enough so that the "brass deflector" at the rear of the ejection port doesn't touch the jig as the flat is bent, same goes for the 93. I haven't built an MP5 so I don't know if their is a lip on those flats or if the brass deflector you riveted on takes the place of the lip...if it does then I would remove it, bend the flat and rivet it back on.

[generalpetres]

ill take a picture of the flat on the jig as far as i can tell it doesn't interfere at all with the jig except the holes being a tiny bit out of sync maybe a couple thou. im going to try and rivet the sling attachment point onto the receiver and attempt to bend the flat tonight, i dont have a ball end mill to create a holder for the rivets so im going to use some 3/8 bolts and some pennies to press the rivets. The pennies will go on the back side where the rivet heads are so the heads will remain round and hopefully not get screwed up when smashing the rivets. Im going to try and stop by my school on Thursday night to use one of the mills and some end mills and reamers to do the barrel pin hole and install the barrel pin and hopefully this weekend i can start the install the barrel and trunnion into the receiver.


I used some bolts and pennies to press the rivets and 2 of the 3 came out great while one of them ended up with the head sticking up off the receiver a bit and a little cockeyed so im going to order a new rivet and redo it as ive spent to much on the gun already to keep going at it half azzed.

[generalpetres]

i havent forgotten about this thread, i have been busy with school and work and am getting over a cold atm, i got a new set of rivets to fix my one screwed up rivet and on wednesday my new cutters should arrive, ordered an 3/16 end mill and no.10 drill bit to do the hole for the barrel pin, going to wrape some tape around the outer flutes on the end mill to keep the end mill centered in the hole so i can create a flat on the barrel, and then i will use the no.10 drill bit to drill thru and then press the barrel pin in. this should be a big/small enough hole for the pin to press into and not be too snug or too lose. the barrel pin is 5mm or 0.19685in, the no.10 drill is 0.1935in which will leave the hole .00335in undersized.

[ar15barrels]

the barrel pin is 5mm or 0.19685in, the no.10 drill is 0.1935in which will leave the hole .00335in undersized.

That's a LOT of press fit for a 5mm pin.
I would get a 0.1960" reamer and run it through before pressing the pin in.

[generalpetres]

i was figuring since most drills will drill over size it would open up the hole a bit but ill order a no.9 reamer as i its never a bad thing to have lots of tools and cutters

[generalpetres]

So i was able to drill my barrel pin hole and like i thought after drilling and reaming the hole is a tiny bit over sized, i used my origional barrel pin and was able to push it in by hand about 1/4 of the way then used a hammer and punch to get in the rest of the way thru, i didnt have to hammer it hard to get it to go. should i remove my origional barrel pin and install my new barrel pin that's a bit over-sized? the new barrel pin i have is about 5.0038mm or .197in where the stock barrel pin is 5.0mm or 1.96875in.

[ar15barrels]

the new barrel pin i have is about 5.0038mm or .197in where the stock barrel pin is 5.0mm or 1.96875in.

What are you using to measure your pin diameters?

[generalpetres]

starret dial caliber and a mitutoyo micrometer

[ar15barrels]

starret dial caliber and a mitutoyo micrometer

Forget about calipers when you are working under 0.002" accuracy.
Put in the 0.0002" larger pin.

[generalpetres]

i installed the bigger pin and while its tight i would prefer it to be press tight as i can still install and remove it with a hammer and punch so i might look into getting a larger oversized pin. i bent my receiver but kind of screwed it up as i was pressing on side 1 instead of 2 so its a tiny bit warped lets say about an 1/8 to 1/16 longer on one side but the bolt slides thru fine. only have it held together with two bolts going to tac weld it up and start fitting everything to make sure it will line up.

[matto235]

Can't you red loctite that pin in? Also I have used a punch to flare a roll pin before to get it to fit, doesn't look like you have that option here.

[generalpetres]

i think the pin should be ok if worst comes to worst i can either buy a larger pin or take the pin to school and knurl a portion of it to increase the diameter.

i got the receiver bent its a bit crooked but not by much maybe a 1/16th higher on one side. I want to weld it my self but dont have a tig machine only a mig welder and i want to do the gun right since i put a lot of time and money into it. can anyone recommend someone to help me finished building my mp5 most just welding the rest of the parts and double checking everything is correct. i test fit the arts the rear stock is a bit of a pita to go on i suspect from the receiver being a bit off. i put all the parts on to see what it would look like in either rifle or pistol and im leaning more towards the rifle as i have an red dot that would look great ontop of this gun.

here is the gun as a pistol:


or as a rifle: My preference


heres me shooting an mp5k in arizona.




I plan on shipping my mp5 once its together and working to wmd guns to have the bolt coated with nickel boron and the barreled receiver coated with nitride as well as the charging handle. the barrel is already coated with nitride so they will plug the barrel. the bolt im having them do everything minus the clips going to have the rollers coated as well.