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Posted: 7/7/2026 4:00:50 PM EDT
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I'm building a semi-auto M16A1-XM177 CAR Commando retro clone upper 10.5" in 5.56. Knowing the shorties can be problematic with the gas/cycling, what do you recommend to ensure a reliably-functioning pistol length gun? Particularly interested in buffer weight and BCG recommendations for the above build TIA |
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Originally Posted By Jake1989: Short barrel problems were only a thing when there wasn't 100 options to choose from for each component. An h2 or h3 buffer along with a properly drilled gas port should be all you need if you aren't shooting suppressed. Even with a can it should be all you need. Mk18 was an H2 suppressed or not. But yeah OP this ain’t rocket science, pretty much just slap an upper on a lower and go. |
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If you want to go with an A5 recoil system, and aren't running suppressed, a 3.8 oz A5 buffer and G$ rifle spring works very well with a 10.3-10.5" upper with a 0.07" crane spec gas port. A Sprinco Green spring would work well too Depending on the can, I'd go up a buffer weight |
“All things are said already, but since no one is listening, it is always necessary to start again.”
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Originally Posted By TxRabbitBane: Someone here has a thread where his 10.5 from PSA started to keyhole sometime after 10,000 rounds. It’s a great thread. Here is a link to Lazyengineers thread on his 10.5” PSA upper with 11,000 rounds. I’d say he got his monies worth on that upper. https://www.ar15.com/forums/AR-15/A-10-5-at-11-000-rounds/122-782686/ |
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PSA Premium 10.5 CHF Upper with BCG This has been reliable for me. I run an H2 buffer. I shoot unsupressed with light handloads to full power NATO. It's never choked in 500+ rounds. It has the FN barrel. |
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Originally Posted By Husky629: PSA Premium 10.5 CHF Upper with BCG This has been reliable for me. I run an H2 buffer. I shoot unsupressed with light handloads to full power NATO. It's never choked in 500+ rounds. It has the FN barrel. This is a good one. I like mine a lot. 10.5 got figured out a couple decades ago. |
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Originally Posted By Husky629: PSA Premium 10.5 CHF Upper with BCG This has been reliable for me. I run an H2 buffer. I shoot unsupressed with light handloads to full power NATO. It's never choked in 500+ rounds. It has the FN barrel. Same setup I've got. It was a blem that was on sale; gassy but no problems with anything I've put in it, suppressed and unsuppressed, even a Spike's .22LR kit works in it. |
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Have had a 10.5 psa railed upper for about 4 years and been pretty damn good.FRT on it for the last couple. At first i had a couple minor issues bolt wouldnt close all the way at times.Took bolt apart cleaned it really good oiled and removed the o ring under the extractor and non issue since then.Not sure on round count but it still has good accuracy.I run an h3 for the frt although it can run on the h2 but had a hiccup one time while trying it so went back to h3. H2 works great in semi mode regarless just had one hiccup in FRT mode. |
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Originally Posted By TxRabbitBane: Someone here has a thread where his 10.5 from PSA started to keyhole sometime after 10,000 rounds. It’s a great thread. I had a 10.5 PSA upper that ran like a swiss watch. During Covid. I sold it off to fund some Knights hardware. |
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Originally Posted By Husky629: PSA Premium 10.5 CHF Upper with BCG This has been reliable for me. I run an H2 buffer. I shoot unsupressed with light handloads to full power NATO. It's never choked in 500+ rounds. It has the FN barrel. I got a couple of these back when they built some with a G rail and gas block. I have beat the wheels off of one with a FRT and never had a single failure. I’ve used everything from wolf to hot hand loads suppressed and unsupressed Wolf didn’t like the h3 buffer and had really weak ejections. I only run the h3 since it slowed down the RPM with the FRT. Best guess maybe 6000/7000rds Replaced gas rings once. Other than that run a few patches and keep it greased and oiled. |
"Never argue with an idiot. They drag you down to their level, then beat you with experience."
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I have a 10.3" (home build: DD barrel, MidwestIndustries handguard, spikes reciever set) that's never given me one issue. My setup consists of an h2 buffer and Geissele Super 42 flatwire recoil spring with a Toolcraft BCG. I'm a Neanderthal and still shoot unsupressed. |
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I have a 8.5" I built my self that is my HD gun. Runs like a sewing machine. Attached File |
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I shoot 10.3" more than any other barrel length, and my main CQBR Block II 10.3" has around 30k rounds through it. Well into its 2nd barrel, but still using the original C158 bolt and Toolcraft carrier. As far as reliability, I would put it up against any other barrel length without hesitation. Despite often going 3k+ between cleanings, shooting almost entirely suppressed, 14k or more of the round count being junk Wolf steel case, using light-charged reloads, constantly shooting either rapid and/or FA/FRT fire, and a lot of general abuse, it has been reliable in the extreme. I've logged every round fired, every single part change, and every malfunction. Over the course of its life, I've logged exactly 3 firearm-related malfunctions. All were failures to lock back on empty, and even then, only when ridiculously filthy. We're talking scoop the carbon out with a spoon. The only other malfunctions that I've logged were ammunition-related (i.e., crushed or improperly seated primers, etc.). Even counting those, the grand total was 7. I have multiple other 10.3" guns with sizable round counts of their own, and they are equally reliable. The standard setup for all my 10.3" guns is either a DD or Colt barrel with a 0.070" gas port, a Toolcraft, Colt, or Microbest BCG, H2 buffer, and a Damage Industries 'Enhanced' buffer spring (the spring isn't so much for reliability as longevity -- they are great springs and can last 20k+). Beyond that, I always swap in a Colt 'copper' extractor spring with the black insert, and add a Viton O-ring. Some would say that's redundant or unnecessary, but it has worked extremely well for me. I see no reason to mess with a winning formula. Otherwise, outside of replacing the extractor spring and adding a Viton O-ring, I don't do anything particularly special. I use quality parts -- Colt uppers, DD/Colt barrels, the aforementioned BCGs and springs; the lowers are mostly Colt with Colt receiver extensions and Geissele triggers. Nothing all that crazy; just proven, quality parts. For lubrication, I use a lightweight grease consisting of Mobil Grease 28 and Mobil 1 5W to achieve a consistency of NLGI 00 or 000 (think apple sauce or ketchup). That said, over the years I've used Superlube NLGI 2 grease and Superlube oil and Redline CV2 and Mobil 1 5W as well (at the same 00/000 consistency). I lubricate generously and clean roughly every 2k rounds, give or take. Although on occasion I've gone well above that. Basically, use a properly ported barrel with quality parts and a strong extractor spring, keep it well-lubricated, and you won't have any issues. |
Practice, the master of all things. - Augustus
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers - G Mk16 10.5" DDC
IG: @cqbr.kurdt
Looking for: Savannah Mk18 RIS II in light blonde/bronze - LMT SOPMOD Gen 1 Tan - Aimpoint Comp M3 w/ Lens Covers - G Mk16 10.5" DDC
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Originally Posted By Teamer: Another vote for the PSA. It’s been reliable. Originally Posted By Teamer: Originally Posted By zoe17: Same as above on the CHF Another vote for the PSA. It’s been reliable. Ditto-any ammo, mag, it don’t care. I SBR ‘d mine, and a YHM Turbo lives on it as a duty rifle. |
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I'd be completely comfortable with a PSA upper and expect it to function fine. This 10.5 started as a free barrel from a friend (no idea the mfg), a stripped no name upper, carbine length gas tube with a regular gas block and an H2 buffer. It's a little gassy, but cycles just fine. I think it has 6 different budget manufactures without the accessories  
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