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Post by hnpwilcox on Sept 28, 2016 14:55:51 GMT -8
I am new here and to Ar rifles. I had a rifle built using the 18" 1:8 twist 223/556 so far I am disappointed with the accuracy. I am using 55 grain off the shelf ammunition, recently bought some 62 grain federal Fusions with no improvement. I am getting about 2 1/2 inch groups at 100 yds. I had this built as a varmint rifle hoping for 1 in or less at 100 yds. Am I expecting too much?
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Post by wfa on Sept 28, 2016 18:21:35 GMT -8
Is it a BHW barrel? What is the profile? Are you using a "mil spec" trigger, or something a little "lighter"? Optics? When you say "varmint rifle", are you talking about coyotes, or something a bit smaller? There are so many variables! There are lots of folks here that may be able to help you out, but we need more information (at least I do!).
Walt
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Post by GLSHOOTER on Sept 28, 2016 18:38:36 GMT -8
Welcome to the board.
Tell us more. Scoped or irons? Bipod, sling, pedestal or bags? Does it have a muzzle device? Is it a BHW barrel?
Greg
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Post by hnpwilcox on Sept 29, 2016 5:52:47 GMT -8
Yes, it is a BH barrel 18" 556 1:8 twist barrel. The gun was built by a local builder (Outlaw Precision Weaponry Almont, MI). I am using a "sled" type rest. Looking to shoot woodchuck and coyote. Bushnell 3 x 9 Trophy XLT DOA 600 scope. The trigger has been modified, short travel 4lb.
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Post by wfa on Sept 29, 2016 6:47:57 GMT -8
Greg has probably forgotten more about BHW barrels and AR platforms than I'll ever know, but I'll make a suggestion anyway.
Have you tried shooting without the muzzle device installed? The muzzle device is a weight hanging off the end of the barrel, and will effect the vibrations (aka "whip"). About half my barrels shoot better without a muzzle device, but this, too, depends on the load being used and the barrel countour. Yes, it's a "crap shoot", but easy to test. It acts exactly like the "BOSS" that Browning and Winchester marketed years back on their bolt action rifles.
Walt
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Post by GLSHOOTER on Sept 29, 2016 10:23:45 GMT -8
I agree the first thing is to pull the muzzle device. I would examine the crown carefully also. I would also buy some Hornady 223 varmint loads and forego the run of the mill FMJ stuff for the next few tests.
Did they square the receiver?
Greg
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Post by hnpwilcox on Sept 29, 2016 12:47:28 GMT -8
Thanks I will pick up some Hornady varmint ammunition. I did pick up some Remington Premier 223 77grain MATCHKING BTHP to try. Unfortunately windy and rainy for the next few days.
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Post by GLSHOOTER on Sept 29, 2016 12:56:52 GMT -8
Thanks I will pick up some Hornady varmint ammunition. I did pick up some Remington Premier 223 77grain MATCHKING BTHP to try. Unfortunately windy and rainy for the next few days. You have a few to start. It will be interesting to see how it does. Greg
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Post by peabody on Sept 29, 2016 16:06:23 GMT -8
One bit of accuracy-trivia I have yet to test, but plan to do so, involves the installation of muzzle devices. The point of concern is the torque on the muzzle of the barrel from the muzzle device, and how that torque and tension on the barrel end/threads creates a varying degree of distortion in the muzzle area and crown as the barrel heats and cools. Crush washers are reported to be the worst method for accuracy, while timing shims are a better. However, shims with "excessive" torque can still create POI shifts. It is recommended by the purveyors of said "muzzle science" to install the muzzle device only finger tight using red loctite and let it sit overnight. But that is only one of many possible causes.
Do you know what checks/methods your builder used? Was the upper "accurized" or "just built"? If the builder took the time to true the upper receiver to improve the contact between the barrel extension and receiver (squaring, as Greg noted), and to keep the barrel nut torque within spec (some say the lower end of the torque spec range is better for accuracy), then I'd say your builder was making the effort to maximize the upper's potential. "Bedding" the barrel extension and receiver with blue loctite is another method used to improve and stabilize the contact between barrel and receiver, though it might just be voodoo. If your builder just assembled the upper assuming milspec means it's all in spec, then he was right. Your accuracy is within milspec. But for varmint hunting, that's not what you wanted.
So here's a list of suspects to consider:
- Optics mount/scope rings - Scope - Stability in upper receiver/barrel (squaring/truing/bedding) - Gas block contacting handguard during firing (Barrel whip - Greg pointed this out in another thread) - Muzzle device - Combination of some of the above - Combination of all of the above
Food for thought...
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Post by hnpwilcox on Oct 3, 2016 15:28:42 GMT -8
Well got some better weather. Shot with and without the muzzle brake if anything a slight improvement with the brake. Changed scopes to a Bushnell 4-12x 50mm that I took off my Rugger 77 .223. Shot the 77gr. matchkings and 55gr Hornady VMax. Off the sled type rest cannot maintain 1 inch group at 50 yds. I do believe my builder is more of an assembler, squaring of the receiver etc. were never mentioned. The gas block clears the handguard by at lest 1/8 inch. So I am still bumming.
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Post by GLSHOOTER on Oct 3, 2016 15:37:31 GMT -8
Well got some better weather. Shot with and without the muzzle brake if anything a slight improvement with the brake. Changed scopes to a Bushnell 4-12x 50mm that I took off my Rugger 77 .223. Shot the 77gr. matchkings and 55gr Hornady VMax. Off the sled type rest cannot maintain 1 inch group at 50 yds. I do believe my builder is more of an assembler, squaring of the receiver etc. were never mentioned. The gas block clears the handguard by at lest 1/8 inch. So I am still bumming. Let your assembler break it down and redo it. Was the extension tight in the upper or was it sloppy? Does the crown look clean with no obvious damage? Was the brake hard to take off? I ask a lot of questions. (VBG) Greg
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Post by hnpwilcox on Oct 3, 2016 16:17:05 GMT -8
The crown was uniform, no mars of imperfections that were visible. The brake was very tight. I mad a barre clamp by drilling a 3/4" hole in 2 blocks of wood and wrapped the barrel with electrical tape to remove the brake. i do not know what you mean "Was the extension tight to the upper?" Thanks so much for the advice. The upper assembly was sent back to BH for a barrel replacement / check so this is the second barrel. I will take the rifle back to the builder to be taken down and reassembled. I am getting discouraged.
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Post by GLSHOOTER on Oct 3, 2016 18:28:09 GMT -8
On the barrel extension I meant did it slide in extremely easily or was it a nice tight fit? If the first bedding it would be an option. The only thing I can think of otherwise is that the gas tube might be hitting inside the key pushing the bcg to the side with pressure that can cause weird accuracy problems. It's easy to check by just pulling the upper and flipping it over running the bcg by hand should tell you quickly if there is interference.
I don't know how much you've used the sled but I have used one extensively. Technique is not nearly as simple as it looks. I would suggest trying a few groups off some bags before calling calf rope. If no go I would follow up with Black Hole directly as they don't monitor this board. To get two nin-shooting barrels in a row would be extremely rare. I've been dealing with these tubes for five years and this would be a first.
Greg
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Post by hnpwilcox on Oct 4, 2016 2:18:11 GMT -8
Will get sand bags out. Thanks Greg
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Post by hnpwilcox on Oct 4, 2016 8:02:57 GMT -8
Greg attached is a picture of the gas tube, there is wear on the end of the tube and some resistance when the BCG is closing but i am not sure if it is the gas tube or engagement of the bolt. Attachments:
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