Recommendations on 80% jigs?

[noozeyeguy]

I'm starting on my first AR build, an M16A1 clone on a NoDak 80% lower. I'd like to hear what jigs are recommended by the CG community? I'm looking at the 80 Percent Arms and Tactical Machining jigs, although I've not settled on any particular manufacturer and am open to any other suggestions.

I have a drill press and milling vise, and have built a couple (or so ) AKs from kits.

Also if anyone has a hot hookup for M16A1 parts kits or barreled uppers, looking for that too. I'd prefer to stay as much USGI as possible.

[echo6cavedog]

Get in on the group buy... You're welcome. :P

http://www.calguns.net/calgunforum/showthread.php?t=1005706

[noozeyeguy]

Get in on the group buy... You're welcome. :P

http://www.calguns.net/calgunforum/s....php?t=1005706

Well crap. A day late and a dollar short.

[Jason_2111]

Check out brokenarmory.com ... best jig on the market if it will fit your lower. I'd suggest popping an email to them and asking if it will fit.

[JAE]

That one looks cool. Lots of drilling though!

What is this about lowers not fitting jigs? I tried three different manufacturers lowers in two different jigs and didn't have a problem. Do tell! And post it in the other thread too.....

[Jason_2111]

A lot of jigs are made by folks also making their own 80%'s... so they design the jig to fit their lowers perfectly. Likewise, jigs made for 80's that are from forgings, like Tactical Machining and such, often won't fit billet based 80's because of the external dimensions.
The first jig I ever used wouldn't work on anything except for forgings... so I ended up selling that off and getting a "universal" one from CNC Gunsmithing.. but then that one had problems with some billet based ones.
I'm currently using the Broken Armory one... fits their lowers of course (which is the brand I've been using), but it's just also made really well. You don't have to do a ton of drilling if you have a manual mill handy... but as far as doing it with a drill press is concerned, it's the best one.

.308 AR's are even worse... the external dimensions vary so widely between brands, than getting a jig to fit ANYTHING other that the specific one it was designed for is pretty dang rare.

[VytamenC Tactical]

take a look at the vytamenc tactical jig it is universal and has drill bushings on both side plates and a life time warranty

vytamenctactical.com

[JAE]

A lot of jigs are made by folks also making their own 80%'s... so they design the jig to fit their lowers perfectly. Likewise, jigs made for 80's that are from forgings, like Tactical Machining and such, often won't fit billet based 80's because of the external dimensions.
The first jig I ever used wouldn't work on anything except for forgings... so I ended up selling that off and getting a "universal" one from CNC Gunsmithing.. but then that one had problems with some billet based ones.
I'm currently using the Broken Armory one... fits their lowers of course (which is the brand I've been using), but it's just also made really well. You don't have to do a ton of drilling if you have a manual mill handy... but as far as doing it with a drill press is concerned, it's the best one.

.308 AR's are even worse... the external dimensions vary so widely between brands, than getting a jig to fit ANYTHING other that the specific one it was designed for is pretty dang rare.

This is interesting because my experience was the opposite. Maybe I got lucky. I tried two jigs: Modulus Arms and 80% Arms and three different lowers: forged from Tactical machining, forged from Modulus Arms and billet from 80% Arms. None of it made a difference. Could you measure and post the differences?

[Jason_2111]

If I recall correctly, the main body thickness varied +/- around 0.030 between brands. There are variances even between brands of forgings... but usually not enough to make a difference.
A while back, my partner and I used to host a build party, and started out with a fixture based on duplicating the internal dimensions of a TM jig. We quickly had to make several modifications to account for the different external features on the billet based lowers. Some had extra material where it's not present on an forging, some used slightly different external dimensions... it was a process of evolution to finally come up with something that fit everything. Even if the jig only makes contact with the flats of the sides of the fire control group and the mag well, you can still run into a small issue if the dimension is different. When this happens, you can put the side plates on your lower no problem, but the top plate (machining/drilling guide) won't quite fit. The best fixtures can adjust for this by using slight oversize or slotted holes for the top plates. Some jigs out there do not, and you can end up with a combination of a lower and a jig that just won't play nice together.

I don't have measurements handy, and of the absolute ****-ton of lowers I've seen, I couldn't tell you which one was or wasn't compatible with which.
The best thing to do is ask when you are looking at a jig. Worst case scenario, you get one that doesn't fit, and you return it.

I guess the best way to sum this up... MOST jigs will fit MOST lowers... but not all will fit everything. Also, make sure the drilling holes have steel bushings. Keeping those holes exactly where they need to be is important.
If you're using a mill, the VytamenC will work just fine. If you're using a drill press (and haven't done it before), I'd go with the Broken armory. More drilling, but easier to finish (more top plates), and a depth guide.

I should add, when it comes to milling versus drill pressing it... I've seen lots of people screw up lowers doing both. I've seen people using a mill and not using a top-plate guide... and then turning the wrong crank and blowing the bit out the side of the fire control pocket. I've seen people not keep track of their depth and blow out the bottom, or cut into the selector lever detent hole channel. Likewise... I've seen the failed results of lots of drill press only attempts. Usually from people thinking they were stronger than they are and not holding the jig/lower solidly enough with an actual vise. These guys used to bring the half-finished lowers full of drilled holes to the milling party and try to run them to clean them up. Huge pain in the butt, easy way to break tools.
If you decide to drill-press the whole thing, no matter what jig you use, give a good watch to the broken armory video on youtube. There's some handy tips in there that will help you keep from screwing up your lower.

[JAE]

Wow thanks! I just measured and your right the billet blank I have sitting here is 0.910" and the forged one is 0.888" so there's 0.022" right there. This shouldn't matter really though as long as it's centered, the jig cuts in spec, and the upper fits well.

I originally started with the 80% Arms jig and made a couple but was concerned with this. Later I bought the Modulus Arms jig and made a couple specifically because they advertised that it would be centered with any lower. After some post manufacture data what I found is that the REAL variance, regardless of lower or jig, was the remaining wall thickness on each side of the fire control. Take a look at all the pictures posted on this forum and you can see it by eye. With BOTH jigs. I thought the Modulus jig was going to make this perfect but it didn't.

For example one lower made with the Modulus Arms: fire control 0.690", left wall 0.077", right wall 0.110" ; same forged lower made with 80% Arms: fire control 0.688", left wall 0.097", right wall 0.092". So I was disappointed in this result as I thought the Modulus would be better. Did I get lucky with the placement of the blank? Why didn't the Modulus do what it said and keep it centered? Is it because I'm doing these by hand? IIRC I wrapped the 80% Arms one in blue painters tape and I think I forgot to do this on the Modulus Arms one. Could that make a difference? If so then why because I thought it was supposed to center it? Lots of stuff and the variable of different lower manufacturers plays a role as well hence my questions.

Currently I have more lowers than I can use personally and am looking for friends or volunteers to make some with the same jigs I used so I can figure some of this out. I'm also posting to different threads and asking guys what jigs they used and to take measurements and post them up. All the work is done with a drill and router so the point is to do what anybody can do not what a professional machine shop can do. I mean you can throw the whole kit in your trunk and go make one at a friends house (which I've done). Hard to do that with a press.

After posting this up 80% Arms is sending me a free jig to make comparisons with. I must say that both jigs are getting a little trashed due to being done by hand. The Modulus Arms one fared much worse and made a quarter of the lowers the 80% did. I'm interested in data from any other lowers made by different jig manufacturers. If anybody has the time to take a caliper to them and post it up that would be great.

[Jason_2111]

That's the issue with jigs that use a top-plate. If it is centered perfectly for a specific body thickness, it will be off any time the blank is not that thickness. And, in some cases, (depending on how they mount their top plates to the jig) it might not fit all together.

One of the other things I really like from broken armory, is the custom mill bit he sells as a tooling set. It's got a super long shank, but only a small fluted area... so the milling part never touches the jig, which makes it keep from getting beat to crap.

[noozeyeguy]

For example one lower made with the Modulus Arms: fire control 0.690", left wall 0.077", right wall 0.110" ; same forged lower made with 80% Arms: fire control 0.688", left wall 0.097", right wall 0.092". So I was disappointed in this result as I thought the Modulus would be better. Did I get lucky with the placement of the blank? Why didn't the Modulus do what it said and keep it centered? Is it because I'm doing these by hand? IIRC I wrapped the 80% Arms one in blue painters tape and I think I forgot to do this on the Modulus Arms one. Could that make a difference? If so then why because I thought it was supposed to center it? Lots of stuff and the variable of different lower manufacturers plays a role as well hence my questions.

Currently I have more lowers than I can use personally and am looking for friends or volunteers to make some with the same jigs I used so I can figure some of this out. I'm also posting to different threads and asking guys what jigs they used and to take measurements and post them up. All the work is done with a drill and router so the point is to do what anybody can do not what a professional machine shop can do. I mean you can throw the whole kit in your trunk and go make one at a friends house (which I've done). Hard to do that with a press.

After posting this up 80% Arms is sending me a free jig to make comparisons with. I must say that both jigs are getting a little trashed due to being done by hand. The Modulus Arms one fared much worse and made a quarter of the lowers the 80% did. I'm interested in data from any other lowers made by different jig manufacturers. If anybody has the time to take a caliper to them and post it up that would be great.

That would be my question (in bold); since the Modulus jig is supposed to center off the buffer tube and front take-down pin (right?), I'm not really understanding why the pocket dimensions would be so off-center.

FWIW, my ultimate plan is to build an M16A1 clone on a NoDak 80% lower. I plan to practice with a couple generic paperweights so I don't make all my rookie mistakes on my $140 limited-run NoDak.

I have a drill press and two routers, a full-sized Ridgid and a Dremel with router base attachment. Any input as to whether or not I need to invest in the midsize laminate router? I'd prefer not to have to buy another $100 tool if I don't have to.

[JAE]

That would be my question (in bold); since the Modulus jig is supposed to center off the buffer tube and front take-down pin (right?), I'm not really understanding why the pocket dimensions would be so off-center.

FWIW, my ultimate plan is to build an M16A1 clone on a NoDak 80% lower. I plan to practice with a couple generic paperweights so I don't make all my rookie mistakes on my $140 limited-run NoDak.

I have a drill press and two routers, a full-sized Ridgid and a Dremel with router base attachment. Any input as to whether or not I need to invest in the midsize laminate router? I'd prefer not to have to buy another $100 tool if I don't have to.

The full size will be kind of big to handle. I have a Freud with a 1/2" collet and 1/4" adapter but would never think to use it on something like this. just too big. Maybe yours is smaller but it won't fare well on a jig with a small base plate. You'll need a lot of support. The small router works on both. As for the Dremel.... I dunno. Not enough power. Too small.

The little palm/laminate routers are really the ticket. I originally wound up with mine for tuning doors in place. For the same reasons and I already had the two tools your talking about. It's the ticket. Yes another $100 but the right tool for the right job....

As for the thickness of the lowers I did just run into a problem. The billet ones, being a little thicker, won't accept the anti walk pins with the little C-clips. Also I have a set of KNS anti walk pins and they came loose after a couple hundred rounds (yes I did use blue locktite). I think the reason for this is because the thickness of the lower. Let me explain: because of the extra thickness I can't clamp down the screw all the way to the shoulder of the pin. What happens then is it binds he trigger by clamping it too tight. So I have to float the screw out and trust in the locktite. I also can't reverse the pin to the hammer because of the way the billet is made. We shall see if the big gobs of locktite I did it with hold after a couple hundred rounds but frankly I think I'm going all forged now because they seem closer to industry spec and I don't like these little issues.

[spankie2.0]

I am not necessarily a fan of Modulus Arms. Nothing about their jig, but their inconsistencies, most specifically their handling of the Calguns group buy. But I digress....

Later I bought the Modulus Arms jig and made a couple specifically because they advertised that it would be centered with any lower.

I don't believe Modulus Arms claims to "center" anything. They use the buffer tube and front takedown as reference points, which also happens to be the centerline. They claim compatibility as long as those two are within spec.

Referencing from the centerline locates all machining in the proper relation to the centerline of the lower and consequently the upper, barrel, BCG, buffer tube. If the wall thicknesses varies, it means the sides of the lower are not equal distance from the centerline. As far as functionality, wall thickness, to a certain point, is immaterial.

Yeah I ordered a Modulus jig. My lower is known not to fit the 80% Arms without mods. But that's okay, I have floor mount drill press and 9 routers to choose from.

[JAE]

Yeah I went over this by PM and by telephone with them for about an hour the other day. They said the same thing: it's the lower. When I get an opportunity to hit a layout table with all the parts I'm going to take some in and see what is what. Until that time it's academic. AFAIK from looking at the drawings the entire FCG could be way off and it probably wouldn't make a difference at all. What I'm measuring is such a small difference from the target (hammer to pin) that you could probably have the FCG all to one side with one wall of the lower paper thin and still have a working rifle.

I wasn't part of a group buy and haven't been involved in any of this until lately; so historically I have no frame of reference about these vendors. I know that all hasn't exactly been "peaches and cream" between them. The rest..... is none of my business. I'm just a consumer.

As for what is happening NOW I just got an entire kit from 80% Arms for free and they tossed in an end mill and a t-shirt. They did this with the agreement that I would take a brand new, unskilled person and have them make a lower then do a write up. This is happening tomorrow and I'll post it when I get a minute to format it. I'm also going to work with them on tips and tricks for improvement and the instructions.

The same for Modulus Arms I just don't have the new parts yet. They asked me to follow their directions exactly and that's what I'll do with the next guy. So when they come in there will be a review for that as well.

For both evaluations I hope to keep using the same lowers. Those are the Tactical Machining forged anodized ones I believe they are made by Cerro. Having a third independent lower maker I hope makes it as fair as possible.

In my rules for the exercise tools that can't be easily stowed in the trunk of a car, or bought at a Home Depot at 9pm, are not allowed. The point is anybody can do this at home with common hand tools. It's what the jig makers advertise let's put it all to the test. Better yet I'm getting guys who have never made one to do the work and just offering advise as they make their own. And the jig of course (provided by the vendor).

More to come.