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Posted: 10/31/2025 6:40:42 AM EDT
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Looking to get a shorter piston upper as I have never had one. Currently looking at a PWS mk 111 mod 2 that with a coupon code I can get for $1080 to my door. Also have thought about the MR556 A4 upper option that would be right under 2k to my door. I always shoot suppressed and just wanted to try something different than a DI gun. So from what I have read PWS seems to make a really good product. Is that the general consensus here? Would there be an advantage to splurging for the HK over the PWS? Also just reading about this cam pin issue deal. Is that something to worry about? |
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The PWS uppers are nice, plenty of good reviews in the pic thread in this forum There’s also the Brn-180 from Brownells (also mfg by PWS) if you want an option that doesn’t need buffer tube. Here’s my gen2.5, they have also released a gen3 that’s slimmed down with different ergos 
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i have a PWS 11.85" or whatever it is (not 11.5, not 12). It's a great shooter, accurate, always runs with a can on it. I don't really notice too much difference vs. other DI guns - recoil impulse is a little different but not enough to write home about. I've probably got 3-4K rounds through it trouble free. I cleaned it once I think mine was the budget version as it was in the 600-700 dollar range |
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I have a PWS mk 111 mod 2 11.85" and a LWRC 12.7" piston upper. Both are great. I shoot the LWRC more...not sure why but I do...I suspect I shoot it more because I have the LWRC lower to it and it's a matched set....I think the LWRC is built a little nicer and is more polished...should be since it is so much more Attached File |
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My current AR-lowered/piston upper guns consist of a MK111 Mod2, BRN-180S and a Spear LT. The Sig is noticeably heavier than the other two. The BRN is the lightest and smoothest of the bunch, but the offside charging handle is a PITA. My only dig on the PWS is the use of the buffer tube and not being able to fold.    If you decide to consider piston-driven options outside of AR-lowered uppers, I absolutely love my Bren 2. They can sometimes be found for about the same $$ (or not much more) than some piston uppers.  |
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Originally Posted By DetroitSounds: Little experience with piston uppers, but I have been considering that MR556A4 as well. Just handled one yesterday. Pair it with a B&T can supposedly a super accurate, soft, flat, reliable shooter. |
As said before the brn 180 is light, it swings like a toy. I like the old school charging handle but if you don’t there’s the gen 3. 
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If a 147 grn 9mm at 1000 FPS is the hammer of Thor then a 165 grn. 40 at 1200 fps must a lightening bolt from Zeus!
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Originally Posted By CJofFL: Hk’s are the opposite of soft, they’re overgassed and oversprung for reliability. Originally Posted By CJofFL: Originally Posted By DetroitSounds: Little experience with piston uppers, but I have been considering that MR556A4 as well. Just handled one yesterday. Pair it with a B&T can supposedly a super accurate, soft, flat, reliable shooter. The A4’s are a bit less so than the original, plus you can adjust how much gas it vents via their overpriced screws. But it’s an awful lot of money for a naked upper. BRN-4 is much softer shooting, though still a bit more violent than a standard AR. This would be my recommendation, slap a 10” G rail on it, and it balances very nicely. Preferably the MK15, having the fixed 1913 sections at the front gives you more options for mounting a LAM on a shorter rail, Primary arms might still have blemulas in stock. 16” midweight barrel, flow 556k, Iris-3, Rein light, and a Razor 1-6 is far less cumbersome than I expected it to be, very similar to the way an M16A4 clone handles. Plan on shaving off almost ~10 punces by swapping to a 13.7” barrel and Iris-4 when that releases. It needs a heavy stock for balance, and I did have to go out of my way to get a G national match 1.3” zero cant LPVO mount, standard 1.54” mounts were too tall for my tastes on the taller receiver. MCX is even more violent than the HK, but its recoil cycle is much faster, with less mass moving, so it tends to jump around a little less. The Virtus is front heavy as shit, so it barely moves under recoil. |
| I have a BRN-4 upper in 10.4 with the chrome lined heavy barrel and a BRN-4 14.5 mid weight barreled upper. I really like them, especially the 10.4 paired with an OSS (Hux) 556K suppressor and the A5 H2 buffer setup. My 14.5 uses a Surefire RC-2 mini and using the same recoil system. The recoil impulse seems to have a more straight back push rather than my DI uppers that tend to push and rise. Both uppers have Geissele rails, Blemula models, but the fit and function is outstanding. I would really like to do an 11.5 or a 12.5 BRN-4 upper, but that's gonna require getting a new barrel and having it cut down, unless Brownell's decides to open up their variety on their barrel selection. |
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I have a 12 inch LMT that I really like but PWS has a very good reputation so i would not have any issues trying out any of there stuff. As for the HK stuff, its nice but like with most stuff, there is a point of diminishing returns. If you have the money, like hk, go for it. |
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I was an early "convert" to the Church of the Holy Piston. I've owned a ton of them over the years. Every model of LWRC (some models I've had 3 or 4 ... .likely a dozen guns in total) Several models of POF (probably 5 in total) Adams Arms HK MR556 (the first and second gen) Several HK MR762 LMT (standard 16" piston and Estonian 14.3" piston) Several PWS (116 Mod-1 and 111 Mod-2 .... several guns in total) Caracal 816 I've also had every generation of the Sig556, every generation of the Robinson XCR, a Robinson 96, several Scar16 and 17s, several generations of MCX, every generation of ACR, Costa Mesa and Sterling AR180s, Gen2 AR180s, Beretta AR70, Galil 386, Daewoo AR100 & DR200, AUGs (every generation), Valmet 76s, several Beretta ARX100, etc etc etc If I were looking for a piston AR today, I would consider a PWS or Caracal. If you want long stroke ... PWS. If you want short stroke ... Caracal. Both are great guns ... these are the two I kept. In fact, I just sold both of my HK MR556 for WAY LESS than I paid. I really like HK, but that tapered bore / no lining is a deal killer for me. If HK would release an updated MR556 with the current generation of improvements plus standard chrome lined barrel, no tool push-pins, and no firing pin spring safety I'd consider it. Until then, the Caracal is functionally a 416. |
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Originally Posted By paigecm1: Well just pulled the trigger on a 12” shovelnose. Can’t wait. LMT would be my third choice in a piston gun or first choice is chrome lined barrels are a "non negotiable". You might want to review the gas plug when you get it. There are different options. If you plan to shoot Russian Steel Case you might find it undergassed too. Use a Carbine buffer and the lightest spring you can find if this is the case. |
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Originally Posted By GaryT1776: LMT would be my third choice in a piston gun or first choice is chrome lined barrels are a "non negotiable". You might want to review the gas plug when you get it. There are different options. If you plan to shoot Russian Steel Case you might find it undergassed too. Use a Carbine buffer and the lightest spring you can find if this is the case. Originally Posted By GaryT1776: Originally Posted By paigecm1: Well just pulled the trigger on a 12” shovelnose. Can’t wait. LMT would be my third choice in a piston gun or first choice is chrome lined barrels are a "non negotiable". You might want to review the gas plug when you get it. There are different options. If you plan to shoot Russian Steel Case you might find it undergassed too. Use a Carbine buffer and the lightest spring you can find if this is the case. What should I be looking for on the gas plug? I run reloads that i load and are significantly “faster than wolf”. I believe I still have a case of wolf put away. What would your number 1 and 2 be? |
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Originally Posted By paigecm1: What should I be looking for on the gas plug? I run reloads that i load and are significantly “faster than wolf”. I believe I still have a case of wolf put away. What would your number 1 and 2 be? Originally Posted By paigecm1: Originally Posted By GaryT1776: Originally Posted By paigecm1: Well just pulled the trigger on a 12” shovelnose. Can’t wait. LMT would be my third choice in a piston gun or first choice is chrome lined barrels are a "non negotiable". You might want to review the gas plug when you get it. There are different options. If you plan to shoot Russian Steel Case you might find it undergassed too. Use a Carbine buffer and the lightest spring you can find if this is the case. What should I be looking for on the gas plug? I run reloads that i load and are significantly “faster than wolf”. I believe I still have a case of wolf put away. What would your number 1 and 2 be? You'll want the 2 Position Gas Plug . LMT's part number is: R-L7S1B6CF. As my above post mentioned, I've owned around three or four dozen piston AR15s and virtually every other piston rifle ever available in the United States. If I were in the market for a piston AR15 it would be a PWS for long stroke or Caracal for short stroke. The PWS is unique because it is a long stroke (basically an AK gas system). The Caracal is closer to a current generation HK416 than just about any other rifle available. The Sig516 was in improved HK416 by the same designers. The Caracal is an improved Sig516 by the same designers. HK416 ... SIG516 ... CARACAL 816 ... see the progression? |
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My DI LMTs are overgassed. The two LMT piston guns I've owned were undergassed. They required a 3.0oz carbine buffer and Springco Yellow light recoil (reduced power action) spring to function with 223 spec (not 556 NATO spec) ammo. |
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I set up a 16" Adam Arms carbine with an A5 buffer tube, RB5007 buffer and Tubb AR15 spring (aka anphibian setup). Tried the Tubb AR10 spring first, but it wasn't cycling reliably. It runs great with my reloads (mostly 50gr frangible). I'm thinking about getting a MK114 Mod2 upper because it's supposed to have a softer recoil impulse than other piston drives. |
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