80% DPMS drawing

[Scott Clearman]

New here, and I'm looking at building a DPMS pattern rifle from an 80% receiver.  I am trying to find a drawing for milling out the FCG and drilling the pins.  I've seen a couple but the dimensions vary even though both are supposed to be for DPMS pattern.  Anyone have a known good drawing?

 

[MikedaddyH]

Just buy a quality jig.

[Scott Clearman]

38 minutes ago, MikedaddyH said:

Just buy a quality jig.

Well,  I really don't want to.  I have a quality machine shop at the house including a pretty nice lathe and milling machine.  If I bought a jig, I'd have to buy a router and that seems like a step backwards.

[shooterrex]

If you have a mill the jig will work fine.

[Scott Clearman]

51 minutes ago, shooterrex said:

If you have a mill the jig will work fine.

No offense, but I'm not buying a jig. That's like telling someone to put training wheels on a race car.  Jigs work fine no question.  But a mill with digital read outs is more accurate and does better work in most cases.  Using a jig in a mill is actually harder because I would have to be careful not to damage the jig.  My end mills have 2" length of cut, which would cut into the jig itself very easily. 

[Scott Clearman]

20 minutes ago, Swiftab said:

Here is the drawing I made.  I machined (3) and they all came out great.  I think all the information is there.  I based these on Noreen Lowers.

 

 

LR308 Low and Vise plates.dwg 113.85 kB · 0 downloads

Thanks.  I am assuming that the final pass in the FC pocket off centerline is with a 3/8" bit?

[Scott Clearman]

Perfect, thanks.

[Scott Clearman]

I do have that, thanks.  I've done several ar-15's and a Glock mag 9mm ar lower.  This will be the first 308.   I'm sure you know, there is lots of info, and it generally all agrees on dimensions for the smaller ar15 platforms.  When I started looking for 308, wow.  Not only does it vary from lr08 to ar10, but even within the same platform I have found dimensions vary as much as .075".  

[Scott Clearman]

I missed the radius call out on the drawing, I had to look at the file on a web viewer since i'm at work.  

Still have one question/concern:  I understand that a DPMS pattern upper with work with both LR308 and AR10 barrels and bolt groups as long as both barrel and bolt group match.  do either the LR308 or AR10 bolt carriers cause any fitment issues with these dimensions?

[Matt.Cross]

1 hour ago, Scott Clearman said:

I missed the radius call out on the drawing, I had to look at the file on a web viewer since i'm at work.  

Still have one question/concern:  I understand that a DPMS pattern upper with work with both LR308 and AR10 barrels and bolt groups as long as both barrel and bolt group match.  do either the LR308 or AR10 bolt carriers cause any fitment issues with these dimensions?

Carriers are functionally interchangeable, no meaningful difference.

[Scott Clearman]

29 minutes ago, Matt.Cross said:

Carriers are functionally interchangeable, no meaningful difference.

So carriers interchangeable, only bolts different from ar10 ro LR308?  SO any carrier and any matched pair of AR10 bolt and barrel or LR308 bolt and barrel?

[Matt.Cross]

20 minutes ago, Scott Clearman said:

So carriers interchangeable, only bolts different from ar10 ro LR308?  SO any carrier and any matched pair of AR10 bolt and barrel or LR308 bolt and barrel?

Correct.

[98Z5V]

8 hours ago, Scott Clearman said:

I missed the radius call out on the drawing, I had to look at the file on a web viewer since i'm at work.  

Still have one question/concern:  I understand that a DPMS pattern upper with work with both LR308 and AR10 barrels and bolt groups as long as both barrel and bolt group match.  do either the LR308 or AR10 bolt carriers cause any fitment issues with these dimensions?

 

6 hours ago, Scott Clearman said:

So carriers interchangeable, only bolts different from ar10 ro LR308?  SO any carrier and any matched pair of AR10 bolt and barrel or LR308 bolt and barrel?

I'm running a fully functional, badass 13.5" gun, which is a complete Armalite AR-10 functional operating group (barrel, gas tube, complete BCG, and full recoil system, from Armalite) in a  DPMS-patterned Aero Precision M5 reciever set, upper and lower (and rail).  Keep the compatible parts compatible as far as operating systems go, but inside the receiver sets, they WILL swap, and work.

[mtchmxz]

On 10/8/2019 at 2:29 PM, Swiftab said:

Here is the drawing I made.  I machined (3) and they all came out great.  I think all the information is there.  I based these on Noreen Lowers.

 

 

LR308 Low and Vise plates.dwg 113.85 kB · 6 downloads

So these dimensions will be correct for the DOMS 80% lower from 80% arms. Right? 

[Scott Clearman]

18 hours ago, Swiftab said:

My lowers were from Noreen.  Check the dimension from the front hinge pin center to the Safety detent hole center.  Adjust if needed.  Your trigger assembly position is established by the Safety detent hole that is already in your 80 percent.

How do you indicate to find the detent hole location.  I imagine using a rod in the detent hole to indicate against, but how do you set it up when you set the receiver upright?

[Scott Clearman]

Duh, brain fart.  After replying it all came into focus.  I was picturing the fire control pocket in reference to the detent pin hole.  Instead its the 3  holes in the side measured off the detent hole.

 

[GKocher]

Scott, I'm looking to mill an 80% AR308 lower, but I can't access the file above.  Could you send me what you used?  How did they/it turn out?

Thanks for any help you can provide,   Gary

[Armed Eye Doc]

3 hours ago, GKocher said:

Scott, I'm looking to mill an 80% AR308 lower, but I can't access the file above.  Could you send me what you used?  How did they/it turn out?

Thanks for any help you can provide,   Gary

Welcome to the forum.  Tell us a little about yourself in the introduction section.

@Scott Clearman has not been here in about 6 months.  Also, it appears that @Swiftab was the originator of the file you are seeking.  He still hangs around here.

[Scott Clearman]

I'm looking at some drawings.  Are folks here milling with a milling machine or doing it some other way?