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Posted: 10/21/2025 6:16:00 PM EDT
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So I thought there was two types of 308 AR aside from the AR-10b. I thought square back and round back was it. I learned the hard way today that PSA uppers don’t fit the Aero M5. I have them both now. So what are my options. If I get a M5 stripped upper, will all the PSA parts fit it? With the barrel line up? Will the bolt and carrier work ok? Or am I better off getting a PSA lower? If the PSA parts will fit, what other stripped uppers will fit properly? Bear Creek? Any other recommendations? |
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Originally Posted By bruh44: So I thought there was two types of 308 AR aside from the AR-10b. I thought square back and round back was it. I learned the hard way today that PSA uppers don’t fit the Aero M5. I have them both now. So what are my options. If I get a M5 stripped upper, will all the PSA parts fit it? With the barrel line up? Will the bolt and carrier work ok? Or am I better off getting a PSA lower? If the PSA parts will fit, what other stripped uppers will fit properly? Bear Creek? Any other recommendations? Never tried that combo but have successfully installed an Aero 308 uppers on a a PSA gen 3 lower. |
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I own a few Armalite AR10 B's, I prefer the Armalite Gen 2 mags over anything else currently on the market. That being said, I wouldn't hesitate to buy an Armalite AR10 A if I was starting over from scratch. The only real difference when assembling an AR10, compared to an AR15, is barrel nut torque. I start at 55-foot pounds on a well lubed upper receiver and torque higher going from there. 70-foot pounds of torque is common, sometimes it's even higher. Because Armalite's B magazines aren't really a viable option now, you are forced to go with the KAC/DPMS/Magpul option. A custom barrel really shines when building an AR10. I own two of Noveske's and one Lilja, all of them are hammers. |
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Originally Posted By borderpatrol:... Because Armalite's B magazines aren't really a viable option now, you are forced to go with the KAC/DPMS/Magpul option. ... I got a few of these to replace prebans I sold into MA a while ago. |
Disclaimer - OP is bad at knowing things, and might catch on fire.
Vet - Op MMAMA
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Vet - Op MMAMA
Every other species kills off their stupid......we cater to them. -- spin-drift
Nobody ever called 911&said I just did something smart. -- TheFlynDutchman
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Originally Posted By Amish_Bill: Not a thing because of a state specific rule? I got a few of these to replace prebans I sold into MA a while ago. Originally Posted By Amish_Bill: Originally Posted By borderpatrol:... Because Armalite's B magazines aren't really a viable option now, you are forced to go with the KAC/DPMS/Magpul option. ... I got a few of these to replace prebans I sold into MA a while ago. They are expensive and have had very spotty availability. I assume that's what he meant. The current Armalite seems very different than the Armalite when I was younger. It just seems like they slide into obscurity a little more every year. It seems very noticeable since they got bought up by the group that owns them now although they've stayed around longer than I would have guessed when it happened. There have been some severe blowouts I wish I would have taken advantage of including B magazines and a complete 6.5 Creedmoor gun for $1200. |
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For some reason, the Bear Creek uppers won’t fit on my PSA lower. The convex curve of the upper does not mate with the concave curve of the lower. I modified the upper so that they will actually work together. I will agree that one should match the upper with a lower of the same brand. https://imgur.com/a/qt3AY07 |
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For years, at least 15 (that's how old my 308 is), I thought you either have the Armalite or DPMS pattern AR in 308 cal. Upper Receiver must have those specifics profile to fit the same profiled lower receiver. I've done 3 assemblies using different upper and lower brands with the DPMS profile, all fit together nicely. Even the latest one is the Genesis Arm 12 gage shotgun upper, it dropped into the Sun Devil Manuf. lower just fine, including the GenArm 12 shotshell magazines. Perhaps we now have a 3rd profile from PSA? And to make it more complex, PSA has 3 generations of 308 lowers and apparently the 3rd generation works with Aero M5 upper according to one of the reviews on PSA. 
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| It's been a few years since I put one together. Back then the general consensus was to always get matching receivers. Parts have a little more compatibility - but you do have DPMS (LR308) hi and low handguards , DPMS or Armalite (AR-10) bolt/barrels. There are others such as the SR25 and small frame receivers but not as common. |
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Originally Posted By bruh44: So I thought there was two types of 308 AR aside from the AR-10b. I thought square back and round back was it. I learned the hard way today that PSA uppers don’t fit the Aero M5. I have them both now. So what are my options. If I get a M5 stripped upper, will all the PSA parts fit it? With the barrel line up? Will the bolt and carrier work ok? Or am I better off getting a PSA lower? If the PSA parts will fit, what other stripped uppers will fit properly? Bear Creek? Any other recommendations? I forgot to answer OP's questions, geez!! 1. Will all PSA parts fit an Aero M5 upper - Apparently you have a PSA upper with the 'modified' DPMS contour so it must have used DPMS pattern barrel to receiver interface + barrel nut, my educated guess is YES, parts should fit into a new Aero M5 upper including BCG and gas tube. 2. Getting a PSA lower - Up to you, which one cost less, a new Aero upper or new PSA lower? This might be your most sure fire way to ensure the assembly will work since your only variable would be the new lower, as long as it is of the same PA10 generation. 3. Bear Creek upper should fit the Aero M5 lower. However to be sure, make a call to Aero with a pointed question 'M5 lower followed DPMS pattern?' And do the same with Bear Creek. Good luck with your AR 308 venture! |
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Thank you all for the advice. The most frustrating part of it is that PSA makes no mention of their stuff not being compatible. This is a gen 3 upper. Plus I could have just got a matching Aero complete upper for a little more than I’m now spending on getting a stripped upper and switching out parts. I have a LMT 308 so I’m familiar that some of these don’t match up well. I did switch out the bolt and carrier just to see. The PSA bolt does seem to function in the LMT, though I didn’t actually fire it. I feel like I’m throwing money at my issues now. The only reason I liked this PSA upper is because it had the A2 front sight gas block. Seemed like a fun toy. Hopefully it all works out now. From doing some research, it sounds like Aero upper will match up fine. My only concern is the castle nut possibly having a different thread pattern. Hope that’s not the case. |
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Originally Posted By Colt653: There is no "mil-spec" standard AR10, like the Ar15 Every company makes there own design. This is why instead of building, I simply bought an ARMALITE I would stick to one company, not mix & match  Super easy to do one's homework these days, mix and match parts to their heart's content, and come up with a rifle that easily outpaces factory offerings. If one doesn't save money, they'll probably come out even- with something that suits them better. The biggest thing is not matching uppers and lowers. Everything else is pretty straightforward. |
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