98Z5V

I tuned out a 0.640 on my Matrix tonight. That thing runs like a champ. I also measured a few 0.660s and a 0.670 from the same exact manufacturer, with the only difference being - matched sets versus rack-grade parts. Is there a difference on what they make? I don't know, but that 0.670" measurement was from the first AP that I ever built, quite awhile ago. All the ones I bought after that were matched sets, but were all at 0.660". Did a machining operation change, somewhere? I don't know. But they all run - because the builder of the lower, with that mag catch-height spec that they made - also machined the height in the upper for the BCG placement. That's the only rational way I can explain why I have a rifle with a mag catch of 0.640" that runs like a champ (same upper), and multiple rifles running 0.660" and running - another with a 0.670" and running... And the distance listed earlier in this thread was 0.687"... So, in one gun, I can be almost 50-thou off of a published number - but that thing runs like a champ, with the exact same mags as all the other ones, with a spec that doesn't meet that number of 0.687", and is under by about 30-thou - but they work?... Great!... One of those 0.660s is my hybrid-bastard-from-hell, too - the 13.5" Armalite/DPMS/Aero gun. That thing will eat any ammo I can fit in a mag. The issue here is the different manufacturers of the parts you're using - and the blatantly obvious fact that there is no "spec" on these things. That's the real problem here. Pick a lower. But pick the same upper. Stick with what "is supposed to work" instead of piling parts together. I'm off my on this - but I still want the details on the parts you've tried. That will tell future members what to stay away from, on combinations that don't work.

I certainly didn't quote you in that, man. No, that was not you...

First - in red above - I certainly hope you're not talking about me. But it you are, then let's just drag that out and get it done with. Next - what upper and lower combination are you running, from how many different manufacturers, and what are you expecting to happen? Please list, by manufacturer, what exact upper, and what exact lower, that you've tried to use here - and what the failure was, with each combination? It's pretty common knowledge that you should use the same upper as the lower, when you build these things, and hoping for a perfect rifle when you mis-match this shiit it pretty much like playing the lottery. ^^^ This tells me alot about the combinations you've tried. I have difference measurements in my lowers - with the different mag catch placement - but they all work with MagPul 20s over two different Gens, and with Lancers. Because I'm using the same uppers, as my lowers. That's MY observations on this mess...

You seemed a little pissy in that post. I understand, kinda - but you need to understand that we're here trying to help you out. So, on that note, you need to give up alot of information. Please allow me to respond, again, before you do - and I'll make my points. I wanted to address this first, though.

I had to shave and cut and polish a bolt catch to get it running, on one of these. I'll try to find the info on it. There are pics up and everything, with measurements of what I took off, and what finally worked. I swear it was that first AP that I did, but I built that Matrix right after that one, too, within a month or two - it could have been that Matrix. I'll find it. I know a couple guys here saved my ass on that Matrix, and sent me the pivot and takedown pins for it - they're different from everything else. @blue109 sent me one, and @jtallen83 sent me the other. Those guys are the only reason that gun is pinned together right now.

One interesting thing I didn't mention about these guns - never had a feeding issue, not even one, from MagPul 20 rounders , either 2nd Gen or 3rd Gen (there was no 1st Gen .308 mags from them), or from the Lancer mags. So, with those difference specs on the mag catch placement, MagPul 20s and the Lancers work just fine. Zero feeding issues on those platforms listed above. I had one hell of a bolt catch problem on one of these things, and I can't remember which one it was. It certainly wasn't the original DPMS LR-308. I think it was one of the Aero setups, but it could have been the Matrix. I documented it here, but I don't know what one it was now...

Any one interested in a .375 CheyTac? I'm only asking because I promised to ask - for my Gun Pusher. I talked him into trading this for a SCAR Heavy that he had. He didn't get the optic. This is not a typical .375 CheyTac that you can "click and order" from Cheyenne Tactical's website - and you can see that in the pics. THis one was custom ordered, and the previous owner had to wait for it to be built. My GP already bought the SCAR Heavy, and paid for it - the buyer that wanted it backed out, his Net-30 went by, and he had to pay it off - so he owned the SCAR. This was an even across trade, minus that bitchin' NightForce, so he now owns the .375. He will sell it - and I don't want him to. I'm still working on the "sweet talk" of "you know, this is already paid for - you owe NOTHING on this gun..." We will be "Demo testing" this thing real soon. We found a farmer a little further south that has over a mile of flat, unobstructed ground, and will let us on there anytime we want. I think we have to pay him back by shooting coyotes when he needs it. Uh, BONUS!... So, officially, this is for sale, but I don't want it to be for sale... If you guys wanna shoot this beast at the Fall Shoot, then DON'T BUY IT!!!... If you guys know anything about this cartridge.... WOW! It's THE distance crusher...

0.670" on an Aero standard M5 lower, upper and lower not purchased together; purchased at different times. 0.660" on an Aero M5 matched set, limited edition ASO set. 0.660" on an Aero M5 matched set, Flag Edition set (the .260 Rem). 0.640" on the original Matrix Aerospace, that is the direct copy of the Ruger SR-762 receivers. Matched set. There's another AP set that's buried, and the original DPMS LR-308 "K-Serial" gun is buried WAY DEEP. I'm not digging those out right now. Those numbers tell me some things about attempting to measure this stuff against a known or published number.

How did a 5.56 guy blow open a thread from 7 years ago - on a .308AR forum?... HOW did you get here?!... 🤩

I wish you could have read my post on gas tube length, gas port postitioning, and everything else I dumped about - that was here 2 days before you posted. It explained it all. That explained exactly why everyone blows off the "short gas tube deal" but why it matters. "M'eh, it's nothing..." It IS something, if you understand this platform.

I did manage to snag one of these tents - but am still looking for another one. The one I found was in the Casa Grande WM store. They didn't have 2, or my search would have been over right then. It was $49 even, plus tax.

Internal depth is 1/8" too short, your buffer is too long... Those two issues together make a weapon that won't cycle. This certainly isn't helping the cycling, or picking up the next round. You had those issues early on? Now, it doesn't cycle...

This right here. That that's a factory upper, so that's aBallistic Advantage barrel. Something is going on, bad - and it's not that second o-ring on the extractor, OP - don't take that out, it's not going to make a single difference. Call a tech rep at Aero, tell them you have videos of the malfunction, and get an email address to send that same vid to. Or, you can send me the upper, and I WILL figure it out quick,ly fix it, test fire it on vid, and get it right back to you.

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They fixed it then - good for them. I'm glad to see that it isn't 7.100" internal, which will make the BCG hit the ears on the lower. Remedied, solved, fixed, on their side.

I would like to know the internal depth (at the top of the extension) on that Aero receiver extension. The only one that I've ever had from them was 7.100" internal depth, for their M5-labeled kit, and it caused me all kind of functional problems, before I traced it to that...

FUK!@!! NOW I remember...

You need to post/host that vid of the BCG not moving, as well as get pics of your brass up, in this thread...

What barrel are you going with on this thing, again?...

He never stated his BCG doesn't move at all - he only stated that spent brass isn't getting out of the gun. First culprit is the BCG length, and that's the quickest thing to solve, by cutting down the poly bumper on the end of it, until that buffer assembly is 5.200" long. The extractor setup isn't the issue, as AP told him - those dual o-rings provide some SERIOUS force on the extractor, and I can say it works, well, myself. The brass isn't getting out of the gun because the BCG is too long - right now, pending internal depth on the rifle receiver extension. The BCG isn't cycling far enough, and screwing everything up - IF the extension is 9 11/16" internal depth, and screwed in all the way...

The cam pin cutout is not in the right place, if you had to round the edges of your cam pin to get the bolt into battery. The better option would have been to take material from the rearward edge of the cam pin cutout, to get the cam pin to clear it. There's plenty of meat in the upper there, to do that.

You can do it with a red dot - this is how we started, Army-wise, with red dots. Aimpoint carry handle cantilever mount.

What upper receiver did you use in your build?...

1. Thank you for the Thank you. We will solve this. 2. Are you absolutely positive on that buffer length? That's 5.313", and it's too damn long. .308AR Rifle Buffers are 5.200" long, so that's an extra hundred thou + that's screwing you up, right off the bat, and that DOES affect cycling. I have a solution to solve this quickly, and at least test the rifle. If it's truly 5.313" long, sand that bastard down to 5.200" long (or file it). Attack that poly bumper on the end of it. If it cycles after that - get a new buffer that's the correct length. For now, don't even worry about that spring... I'll address that spring if we can solve the function of the rifle, first. 3. Good - run it WET. I'm talking about almost dripping-wet, too. .308ARs need ALOT of lube to break in and function. Lastly - will you measure the internal depth of your receiver extension for me? Measure at the top part of the extension, not the base, where the buffer retainer pin is. Top, only - that's the only thing that counts. Stick a tape measure down that until it bottoms out, grab the measurement at the end of the extension - and the extension should be flush with the top of the lower receiver ear. If it's less than flush, it's not screwed in all the way, and we can address that, too. You should see a measurement of exactly 9 11/16". Not more, not less. Right on the money. Lemme know...

Forgot one thing about the SS'19 Shoot = JB Matt. On Sunday, he went nuts on the .260. I think he went through 4 x 20-rd mags. He was literally putting a smilie face on the 300-yard target, after it got fresh paint - I WISH I had a picture of that, because it was a pretty good face, and it was damn funny watching him do it. He had such a good time with that gun - that he has everything getting delivered for his own next week... He's going 6.5 Creedmoor on his, because he has access to an abundance of 6.5C brass. In the next 3 or 4 weeks, we'll get that thing out and shoot it at distance. Might as well zero it, break in the barrel, and whack 1k all at the same time.