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Posted: 9/22/2008 6:55:24 AM EDT
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I'm very seriously considering the PWS Piston Conversion for my SBR (when approved paperwork arrives). For those of you who have had the PWS conversion, how has (or hasn't) it affected accuracy? |
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We build brand new Gas Piston Uppers using the PWS Gas Piston System. Our uppers are called the Addax GPU. We are going to be conducting some full auto testing of our SBR upper with PWS next week. I will also try to squeeze in some accuracy shots into the mix if I can and report back.  
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Accuracy really would still depends on the barrel of your choice.... I ran a PWS uper with Diemaco cold hammered forged C8A2 barrel for the past year shooting various ammo out of this upper... The best group are with the Hornady TAP 75GR, I was able to group in the 1.5-2MOA using a Leupold MR/T 2.5-8x scope with M1 turret and TMR reticle mounted on an ADM scope mount. Diemaco barrel are free float via a Daniel Defense Lite 9.5FSP rail. lower using a single stage Accuracy Speak trigger group. groups shot on sandbag off the bench. usually I just run an EOTech and that usually return in the 3MOA on the square range. PWS group pretty close to a DI gun and shoots very similar to the recoil impulse of the DI gun also. I also ran some suppressor test on it recently, the supressed rounds using a GemTech G5 can returned about the same accuracy as the unsuppressed version... |
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WHETHER PISTON OR DIRECT GAS IMPINGEMENT, ACCURACY IS ALWAYS GOING TO BE MOSTLY ABOUT THE BARREL, BUT TO A CERTAIN EXTENT THE COMPONENTS AND ASSEMBLY, AS WELL. THIS MSTN CUSTOM UPPER WITH A NOVESKE N4 BARREL CUT TO 12.5" SHOT (BARREL WEIGHING A MERE 20 OUNCES) FIVE INTO 0.80" AT 100 YARDS, WHEN DIRTY:   OF COURSE, I DID USE A BIG NIGHTFORCE NXS SCOPE IN A LARUE SPR MOUNT, A COLT M16A1 LOWER WITH A BEAUTIFUL KNIGHT'S TRIGGER, BLACK HILLS RED BOX 50 GR VMAX, AND A 40 LB SANDBAG UP FRONT WITH A BUNNY EAR BAG IN THE BACK. BUT, I HAD CONSUMED THREE TRIPLE LATTES THAT DAY ... GOOD SHOOTING, WES GRANT MSTN.BIZ |
THERE IS A TENDANCY TO OVER-GAS PISTON UPPERS. DON'T ASK ME WHY. MAYBE IT'S TO OVERCOME THE SUPER-HEAVY BUFFERS, HEAVY DUTY CHROME SILICON RECOIL SPRINGS, AND CHEAP, WEAK AMMO SOME FOLKS INSIST ON USING. LESSER QUALITY COMPONENTS ALSO TAKE MORE GAS TO RUN, DUE TO TOLERANCES AND FINISH. PAUL AND I ARE AR' PARTS SNOBS. WE ONLY USE THE BEST OBTAINABLE. THAT'S WHY WE SETTLED ON THE PWS SYSTEM, BTW. WHEN DOING A NEW BARREL LENGTH WITH THE PWS SYSTEM, WE COME UP WITH THE SMALLEST GAS PORT WE THINK WILL WORK, AND THEN GO DOWN TWO NUMBERED DRILL BIT SIZES. WE LIKE TO WORK OUR WAY UP TO "ENOUGH". WE USE STOCK LMT RECOIL SPRINGS WITH H BUFFERS IN THE PWS PISTON BUILDS, NOT THE HEAVIER STUFF USED IN D.I. GUNS. WE WANT OUR GUNS TO RUN "SMOOTHLY" WITH MINIMUM MOVEMENT UNDER RECOIL. ONCE WE GET WHERE WE THINK WE NEED TO BE IN TERMS OF GAS PORT SIZE, WE DO SOME FULL AUTO TESTING TO CONFIRM WE'RE GETTING WHAT WE'VE COME TO UNDERSTAND IS A SUITABLE RATE OF FIRE, TO ENSURE FURTHER WE'VE GOT IT RIGHT FOR A GIVEN BARREL LENGTH. SOME OF THIS DATA ON THE 10.5" BARREL LENGTH WE'VE SHARED WITH YOU EARLIER IN ANOTHER THREAD ON THE PWS PISTON SYSTEM. YOU MENTIONED APPARENT RECOIL AS AN ISSUE; I AGREE. BUT LET ME TELL YOU THIS: I HAVE AN ACCURATE 12.5" UPPER WITH A NOVESKE S/S BARREL. I ALSO NOW HAVE AN UPPER WITH A NOVESKE N4 BARREL CUT TO 12.5" I RUN WITH A PWS PISTON SYSTEM, THAT'S NOT TOO SHABBY OFF THE BENCH, EITHER. IF YOU DID NOT KNOW WHICH WAS WHICH, YOU COULD NOT TELL FROM THE RECOIL WHICH GUN WAS THE PWS PISTON RIG AND WHICH WAS THE D.I. GUN. IF YOU THINK YOU HAVE A BETTER WAY TO BUILD UP A PWS PISTON SYSTEM UPPER, I'D REALLY LIKE TO KNOW WHAT IT IS. GOOD SHOOTING, WES GRANT MSTN.BIZ |
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