This is my initial range report on my Colt 6721/6920 hybrid which has the Primary Weapons Systems piston kit installed on it. It’s a very nice kit, retails for around $399.99. It features an adjustable gas system with a pinned gas block. The piston is in the gas block and the op rod is attached to the carrier key. The system uses your existing carrier. Primary Weapons Systems removes your DI key and replaces it with their key, with the op rod attached to it. The PWS is the lowest height I’ve seen for a piston driven kit, so low that it fits under many different rails to include the excellent Daniel Defense and LaRue to name just a few, it’ll also fit under plastic M4 handguards.
I fired just over 350 rounds with it, in about 45 minutes, at the NRA Range; 200 of that was Wolf graciously donated by M4C member themadhatter (thanks dude! ). The other 150+ rounds was a mix of plastic cased Natec (yes the really weak stuff), American Eagle, Guatemalan, XM193 and some other stuff. It had 2 jams. One with Natec which was a weak round which didn’t get ejected, I could tell by the recoil that the bolt didn’t move far enough back for ejection. The other was with XM193, an empty was ‘stovepiped’ in the upper with a live round below it, this one I can’t figure out if it was ammo, the rifle or shooter induced.
I used 5 different PMAGs for the shooting that night and had it generously lubed with WeaponShield. The Wolf ammo ran flawlessly and was a mix of polymer coated and lacquer coated.
The only sight used during the initial test is an Aimpoint. I sighted it in quickly at 25yds for a 1" low POA/POI and didn’t shoot for groups, initial testing was just for function. The Aimpoint on the gun is my M4 T&E model, I’ll be doing a write up here on M4C about it and my T1 very soon. There are no iron sights installed on the rifle currently. I’m waiting for my LMT front sight on backorder. I’ll be using a LaRue rear sight. I’ll update this post from time to time with my findings. The bolt is a BCM unit with a 0-ring, no gas rings, BCM cam pin and firing pin. Carrier is a Colt M16 model. I ran it with a H2 buffer. I’ll also be testing with a Enidine buffer, H buffer and a H3 buffer. I also plan replacing my A2 compensator and getting another AAC Blackout flash hider for it for testing with a my M4-2000 Mod 07 suppressor. I plan to use it on friends registered M16 within the next few weeks. The balance is very good with the VLTOR E-MOD stock, I tried one of my CTR stocks on it but that made it feel muzzle heavy.
I didn’t clean the rifle after shooting at all but did wipe off the carrier with a paper towel while showing it to some customers yesterday at the shop, as it was oily not really very dirty.
Thanks for the review. It looks like a really nice system but I want to see how it does long term before diving in head first. My hat is off to you for diving right in.
I’ve been shooting a preproduction model for 6 months or so without any trouble. I now use it as a loaner weapon for other LEO/MIL to shoot just to keep the round count up, but my mistake was not having guys log how many rounds they put through it, so I’ve lost track.
What type of rifle (Colt, LMT, N4) do you have the PWS system? Can you guesstimate how many rounds you have put through the system? How often have you had to clean the system and/or rifle? Any additional information is appreciated.
looks very similar to my PWS setup
i went for a midlength system, though. used a DD 9.0 rail and vltor MUR.
sent it back after the first tests to adjust the size of the port so it’d lock back on an enidine buffer and will test it next week.
Thanks for the review. The PWS piston setup might be the best piston design (to date). Am going to have them put the system on a Noveske 14.5 SS setup.
Assuming Robb, that you have spent some time with the 416, how does the PWS system recoil compared with the HK? Same? Softer?
I’ve only shot about 50 rounds through a 10" 416 (30 of that was full auto). It feels very similar but a little different but then were comparing a 10" gun to a 16" gun. I’d like to try them side by side (maybe somebody will bring a 416 to the Vickers class ). The PWS feels more like a slow heavy push to the shoulder with about 2/3rds of the muzzle lift of a DI 16" gun but definitely feels different than DI guns. I think the Enidine will soften the push, a brake may intensify it just a little.
i shot my midlength PWS alongside a carbine PWS, and there’s definitely a difference - the middy is much softer. both had FSC556 brakes on them.
compared to DI 16" rifles, my midlength PWS with enidine was about the same, or a bit softer than a DI. the carbine PWS had a bit more recoil than the DI.
how much of it was due to the brake, we didn’t know, but both had very little muzzle rise, as expected, with the FSC556’s.
the thought didn’t occur to me - what are the benefits it’d negate?
my reason for choosing it was that i figured it’d be softer shooting than a carbine version, and it was. that was my only reason for choosing it.
softer shooting platform with same barrel length - made sense to me.
edited to add - i also knew that the first PWS conversions would be carbine length, so i wanted something different just in case i got a chance to compare them side by side. just another data point.
Thanks for the great pics and the review Gotm4! Sounds like the two jams were the result of the ammo. Looks like PWS has a sure thing with this new system.
I am going off of LAV’s “benefits of a piston” list:
running a short barrel
running lots of auto
running shit ammo (not by choice)
running suppressed
any/all of the above
Your reason is a new one on me. I’d heard (never shot one) that middys were already very soft-shooting. LAV told us that if your needs are not on the above list then the 16" DI gun is GTG. The middy seems to be the best option for a GP carbine.
those reasons don’t really apply to me (except for the shit ammo once in a while) as my perspective is MUCH more basic/rudimentary than that, being just an enthusiast/hobbyist.
‘which configuration will i like shooting the best?’ pretty much sums it up.
PWS probably makes the middy kit so that you don’t have to buy a new barrel assy (if you own a middy) when getting a PWS installed…just my edumicated guess.
). The other 150+ rounds was a mix of plastic cased Natec (yes the really weak stuff), American Eagle, Guatemalan, XM193 and some other stuff. It had 2 jams. One with Natec which was a weak round which didn’t get ejected, I could tell by the recoil that the bolt didn’t move far enough back for ejection. The other was with XM193, an empty was ‘stovepiped’ in the upper with a live round below it, this one I can’t figure out if it was ammo, the rifle or shooter induced.
). The PWS feels more like a slow heavy push to the shoulder with about 2/3rds of the muzzle lift of a DI 16" gun but definitely feels different than DI guns. I think the Enidine will soften the push, a brake may intensify it just a little.