My 80% Lower, DPMS Build

suzukiray · December 31, 2014

Can anyone share any experiences they've had or am I the only one building 80%?

Ray.

Edited December 31, 2014 by suzukiray

98Z5V · December 31, 2014

Hey brother, didn't mean to make it sound like only a few people can do 1k yards with this cartridge - not the case. With the right amount of elevation adjustment in the scope, it's not bad. You just have to account for wind to get it there. You can take it further, too. Routinely taking it to 1,500 is gonna require a badass rifle setup, and you doing your part everytime.

On the gap between receivers - 0.060" is a pretty thick feeler gauge. Does that go all the way through both sides? Or, is that rocking the upper in the lower, and getting that kind of gap on one side? Seems excessive, but I haven't measured any of mine for that gap before.

edgecrusher · December 31, 2014

Can anyone share any experiences they've had or am I the only one building 80%?
Ray.

Wow, I thought this was .308 you were talking about. I would expect some tolerance stacking without a milspec, but .223, unacceptable

98Z5V · December 31, 2014

It is a .308 80% he's working on. Silly.

edgecrusher · December 31, 2014

Ok, now back to the space between my lower & upper receivers on the 80% 223 stuff please??? Anyone got answers for that one?
Ray.

Sorry, I must've misread this. Lol

98Z5V · December 31, 2014

Whoa! I thought he was talking about a gap on the .308 set! <lmao>

Ray, what's got a gap, and how much?! <laughs>

suzukiray · December 31, 2014

Guys, go back & read post 10 on the first page. I am referring to the 223 lowers I bought & am building right now. I have the jig for it but have not machined my 308 yet. I want to wait till I have the upper for the 308 so I can test fit it while I am at the mill with the lower. The gap I am seeing in the 223 lowers I haven't measured but looks to be about 60 thou. Tom, Call me at 714--356-784five & I will send you the pic I took if your phone will get pictures. Thanks guys & sorry for the confusion.

Ray.

DNP · December 31, 2014

He's gonna fit in good. He derailed his own thread.

98Z5V · December 31, 2014

I love it, Ray!!!

I'm not feeling very well right now - blue gave me his Ebola at the range-day festivities. I'll try to give you a shout tomorrow afternoon, after work. <thumbsup>

Hueblerking · December 31, 2014

Ray, are both 80% lowers from the same manufacturer? I've finished milling one, but I'm waiting on my upper. You have me nervous...

Happy to share details on how mine fit together when it all gets here.

Rsquared · December 31, 2014

Thanks guys & sorry for the confusion.
Ray.

HIs tag line says it all. Beware! <lmao>

And being a friend of Dirk's shows that he obviously doesn't have any taste. <nutkick>

Edited December 31, 2014 by Rsquared

survivalshop · December 31, 2014

Question is , how really large is the gap & does it hinder the function of the rifles action. I can see through mine when put up to the light , but how much of a gap is the concern . One would think that those making the 80% lowers are adhering to Mil Spec's , but who knows . I know of some using the Tactical Machining 80% lowers & Jigs ,with out problems , I have no experience with 80 % lowers myself .

suzukiray · December 31, 2014

These lowers are from Vision Armory AR15 Parts. I have a Bushmaster upper for my brown build & a gun kit upper I bought from Daytona Tactical for my son's first black gun build. It is the same problem with BOTH lowers & their uppers having the gap. I will get the feeler gauges out shortly to measure the exact amount of gap. Just putting the pins in & holding them up to the light looks like close to 60 thou gap between them.

Ray.

Toolndie7 · January 8, 2015

Im kind of late to the party. But I just picked up a TM 80% ar15 lower and one of their uppers. Machined the lower and found a .015 to .020 gap, no where near your 1/16", damn! I ended up machining my own over sized take down pins and re boring both pin holes. I dont think you would be able to take out .060 worth of gap without breaking out, but it might be worth looking into if it bothers you that much. I guess I cant really complain about my gap because I got the upper and lower for like $75.

survivalshop · January 8, 2015

When you alter your pin holes ,you might alter the Upper Receivers line bore with the Lower Receivers , Extension .

As far as the gap , I would dry fit a complete rife & see how it functions & note any wear marks from the function tests , If all OK , Build it & test it .

I would assume & that's a big assumption , that all these 80 % Lowers are made to MilSpec's. <dontknow>

lakeracer69 · January 9, 2015

When you alter your pin holes ,you might alter the Upper Receivers line bore with the Lower Receivers , Extension .

As far as the gap , I would dry fit a complete rife & see how it functions & note any wear marks from the function tests , If all OK , Build it & test it .

I would assume & that's a big assumption , that all these 80 % Lowers are made to MilSpec's. <dontknow>

This plus 100.^^^. Don't be so fixated on the gap between the upper and lower. Buy a good barrel and trigger, use good ammo.

Also make sure that the spring on the ejection port door doesn't extend up into the port. If the ejection port door opens with difficulty by hand sell the whole thing. LOL Please note that these last two sentences are nonsense as is the perceived "gap" between uppers and lowers.

YMMV

DNP · January 9, 2015

How is he supposed to sneak up on zombies with that damn rifle whistling in the wind?

suzukiray · January 9, 2015

An update: I called Vision & they told me to return the lowers. They are sending me forged lowers as replacements. Apparently these were cast lowers they sent me & had issues & they had just fired the machinist in the shop. I told them that I also had to "fix" the jig they sent me as the trigger/hammer pocket wasn't wide enough to get the trigger assembly down into after machining. They said they would replace that also & would check everything before it all ships out to me. These 5 lowers & the jig were on sale before Christmas for $299.00 but were cast lowers, which they didn't state. The forged lowers are $23.00 more each but they are upgrading me due to the lost time I have in machining the two I did. It will be interesting to hear what they have to say when they get these back & what I see when they send me the new ones.

Ray.

DNP · January 9, 2015

Clean livin pays off. Sucks to lose the time you put in, but good luck with the new ones.

survivalshop · January 9, 2015

Cast ?

suzukiray · January 9, 2015

Sure did seem like it the way they machined while in the mill. I had powder coming out of the holes I had drilled before milling the trigger group pocket. Even my CNC buddy, who owns the mill I used, said they machined like a casting. Go figure!

Ray.

lakeracer69 · January 9, 2015

Maybe Sintered Aluminum? I looked it up and it exists, although I don't know if it would be feasable to use in this application. I saw no properties correlation to other grades i.e. 2024,7075, A356, etc.

I used to machine pure sintered Molybdenum for high temperature parts. It would leave a powdery dust insted of chips. It also chipped off on edges so you had to be careful of cutters and toolpaths. In some respects it machined like cast metals.

You might ask them about it, I'd be interested to know too.

shibiwan · January 15, 2015

Greg, the 80% lowers are legal if you complete the machining yourself and use it to assemble a firearm for your own use. As long as you retain ownership of it it is legal. It doesn't even have to have a serial number! If you want to transfer it to another person I believe you have to engrave your name, location and a serial number on it and submit a form to the ATF, much like you do when you manufacture an SBR. I am not positive on that last part but that is the way I understand it. Shibi might be able to say for sure since he has a manufacturer's license.

It's legal to complete an 80% lower for personal use. No serial number required but it remains "for personal use". The ATF recommends engraving your name + address on it.

In order to sell the firearm, you have to file a Form 1 and the name/address engraving becomes a requirement.

In order to sell a "personal use" unseria

slugger43 · January 15, 2015

I'm about to start an 80% .308. Got the lower and jig from 80percentarms.com. Appreciate the info on required or not required ID on the lower. I intend to have some sort of identifying info, to be certain i can identify the gun should it ever be stolen. Hope to get started on it next week, time permitting.

liber · January 23, 2015

Also, their jig was to narrow after the trigger pocket was cut & I had to open it up another 10 thou, 5 thou per side, just to get the trigger down where it was supposed to be.

I'm not expert and have only milled a handful of lowers, but the AR-15 jigs are specific to forged or milled lowers, AFAIK, as they measure differently. Most of the LR-308 lowers are billet (some forged are coming on the market), so most of the jigs are for billet. For AR-15s using the wrong jig will put the templates off center in my limited experience. The other problem is that on AR-15s, the trigger guard is more often than not integral to the billet lower, and doesn't use the trigger guard as the forged lower does from the LPK. That presents a problem on some jigs as the trigger guard hangs below the jig bottom. That wasn't a problem to mill the pocket, as the center of my kurt vise has an opening over the screw, but when drilling I needed to use a small trestle block to hold the fixtured lower solid against the vise jaws, otherwise it would rock on the intregal trigger guard of the billet lower.

Make sure you have the correct drawing, and keep in mind that the trigger control group pocket is the same as on the AR-15, just a different location on the LR-308 lower. In reality the LR-308 lower has way thicker wall for the TCG opposed to the AR-15 which has very narrow walls and less room for error.

In each of the lowers I've milled, the trigger opening has always been the one piece that needs to be worked on with extra milling or some file work. I find it is actually just better to measure to the center and mill it out by hand, rather than using the trigger template. I've had them off center where the side of the trigger rubs the side of the opening, and have had them too short and the trigger rubbing on the front of the opening, etc...I've had it seem as if the trigger fit, but it was rubbing and would prevent the pins from going in easily. That seems to be the problematic area for me. <dontknow>

The jigs are useless for precision work, which is why I measure by hand. But mine got the holes correct for the safety/trigger/hammer, so that along with being able to hold the lower to do the work on was worth it alone. As a bonus, the templates were the same for both the AR-15 and LR-308 so I only needed to buy a set of extra side plates.