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1/25/2018 7:38:29 AM
Posted: 9/29/2005 2:03:55 AM EST
Hi all. I have an OPS Inc type brake collar that I may have a problem with installing onto a WOA SPR SS 18" barrel. When I hand tighten the brake onto the barrel (without a peel or crush washer), it looks like it would need a quarter of a turn more for it to properly index. I don't want to torque it anymore as I feel that doing so will damage the barrel shoulder.


1. Would I have to get work done on the barrel shoulder or brake itself for proper indexing?

2. I have seen that most of the SPR type brakes installed on SPRs are done so without the use of a crush or peel washer. Would there be a difference in accuracy if I used a crush or peel washer for it to index.

Thanks for any feedback.
Link Posted: 9/29/2005 3:16:00 AM EST
Assuming threads at muzzle are 1/2 inch by 28 threads per inch and a 90 degree (1/4 turn) to topdead center. 1 inch divided by 28 TPI = 0.0358 inches per thread times 0.25 (1/4 turn) = 0.009 inches to be removed from the rear of the muzzle brake. It would be best to have a machinist do this for you. I would personally remove 0.008 inches and let 'crush' when torquing the MB take care of the last 0.001 inch. Good luck. Charles the Gunsmith.
Link Posted: 9/29/2005 6:27:10 PM EST
Thanks for the input and formula. In lieu of having a gunsmith do the brake work, would a peel washer be adviseable for proper indexing?

Link Posted: 9/30/2005 5:03:54 AM EST
I have not seen a difference in accuracy using crush washers and peel type washers.

I have a target with one .30 cal hole from 3 shots with a 10.5" M4 in 5.56 using a modified A2 flash hider installed with a crush washer. Shot at 25m while zeroing Eotech. Obviously not as impressive as one hole at 100m, but it's still less than 1 MOA. Point is, once installed it is a constant, not variable, change to the barrel. Your point of impact may shift (most likely not), but your group size should be similar.

Point of impact shift would most likely occur if the brake bore is not perfectly concentric with rifle bore. Take this to extremes, when adding a suppressor (much heavier and longer than muzzle brake) I get a POI shift on less than 15% of the rifles tested.

I prefer crush over peel.
Link Posted: 10/6/2005 10:58:40 AM EST
I have a similar barrel and used a crush washer to get it to index correctly. With the thread protector on it is not even noticable.

Too me it is simpler to add a washer than machine the muzzle device. Besides no one going to care what it looks like as long as it shoots.

PS. Never had a accuracy problem when using a crush/peel washer. The inside of the barrel is what matters.

Hope this helped!
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