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Posted: 10/18/2007 9:08:59 AM EDT
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Hello, I've got an upper that I put together that should, on the face of it, work like a champ. It's got all the right parts... (see list below) but it's just never quite worked right. First, it's never really shot very well. I mean, 1 MOA 5 shot groups at best, despite my best efforts at feeding it match ammo. Average is more like 1.5-2 MOA, even with known-good 'accuracy loads' that shoot and cycle well in everything I've ever ran them thru. I have a wee bit of experience shooting precision rifles from a bipod, so I think we can rule that out. Second, it's been somewhat fussy about locking back on an empty mag or single-shot block (such as a Bob-SLED). I've tried removing all the 'extras' such as extended bolt catch, CWS, etc. and even tried installing a JP gas block, but no joy. Rifle specs: RRA A4 upper, bolt carrier assembly & charging handle Tubb carrier weight system WOA 20" Service Rifle barrel (1" behind gas block, .750 forward) threaded, w/ Miculek brake installed YHM customizable float tube, w/ rail and adapter for bipod Harris BRMS 6-9" swivel bipod w/ Pod-Loc Larue SPR-E 30mm scope mount Nightforce NXS 3.5-15x50mm scope w/ NP-R1 reticle LAR/Grizzly lower Jewell 2-stage trigger SPR extended grip Magpul PRS stock Schuster extended bolt catch Any ideas or suggestions as to where to start looking would be much appreciated. It's getting to the point where I'm beginning to doubt that WOA barrel... this isn't the first one I've had, but the others just clustered the shots into little bitty groups right out of the gate. Thanks, nuk |
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Thats what I mean about not following... if you read my original post, I *have* removed all these things at one time or another. Both individually (as in remove piece 'A', then put it back) and collectively (remove piece 'A', then piece 'B', then piece 'C', etc.) and it made no difference. FWIW, I've used the Tubb CWS on both my Service Rifle upper (another WOA 20" SR tube), and on my space gun upper (WOA 26" tube w/ extended gas port) with no problems on either one. I'm not saying it couldn't possibly be the problem this time... but it'd seem damn odd. Thanks, nuk |
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Can you remove the brake and try the barrel bare? I asked John Hollinger about this issue, that of FS's and brakes being a factor in accuracy when they are tightened, and IIRC, he was not sure about whether or not it mattered. There is some debate as to the harmonics being effected by them. By the looks of all the parts, I can see why you are not happy. If you can, try it bare muzzle. If it still shoots not so good, try a different scope. Outside of those two things, I would suspect perhaps you have a bad barrel crown or just a barrel that's not going to produce. I'm no expert, this is just my thoughts... |
Well... thats interesting.  Took the Miculek brake off (darn thing was on there tighter than I would have imagined, and put the Adco thread protector on instead. Gun shot mostly better... I didn't have any of my 'good' ammo handy (as in none at all!) so I was stuck using some blaster stuff I had available. The gun grouped a little under MOA w/ this stuff, which is about all the better I'd expect anything to. Next test will be with some ammo loaded up from a 'known-good' recipe; I've got my fingers crossed that the results will be what I'm hoping. Gotta work this weekend, 12 hr shifts so odds are I won't be able to get to the range again until Monday. Still had the bolt fail to lock back a couple times. The weird part is that it does it mostly with heavy bullet loads (75-77gr) but almost never w/ light bullets (50-55gr). I guess I can pull the CWS out, but it seems awful odd that it'd affect just this one upper, and only w/ heavier bullets. |
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