Compensator changes zero, a lot

bryanshoot · February 11, 2017, 09:50 AM

Hi Bryan here, first time post. I'm a long time shooter-reloader, 40 yrs. Two years ago I got into ar's. 8,000 rds. My latest upper has a 18" stainless barrel rifle gas with comp. Not being happy with accuracy (5moa) I removed comp, accuracy improved but point of impact changed 10" at 50 yds. I'm thinking comp is problem and ordered a new one. My question is should a muzzle device change zero that much?
Look forward to joining this forum

Art Eatman · February 11, 2017, 11:00 AM

All manner of things affect POI. Muzzle brakes, comps, suppressors, muzzle dings, you name it. The amount of change seems to be "luck of the draw".

Bartholomew Roberts · February 11, 2017, 01:13 PM

What Art said. Anytime you add something to the barrel, you change how the barrel vibrates from shot to shot. You don't even need to add something, just lay your barrel against a rest or wall for a quick demonstration of how that changes point of impact.

Barrel rigidity seems to help a lot (heavier profiles and shorter barrels) with minimizing that shift; but it happens. Unless you plan on removing the compensator periodically, I'd just rezero and call it good.

bryanshoot · February 11, 2017, 03:05 PM

I expected a little bit, but thought 10" at 50 yds extreem

Theohazard · February 12, 2017, 02:55 AM

10" at 50 yards is pretty extreme. I'm guessing there's something unusual about that muzzle device.

Also, welcome to TFL!

Targa · February 12, 2017, 08:18 AM

Yeh that is really extreme. I have a Gamma 5.56 brake on my AR, pretty useless really but I had a store credit. I re-zeroed the rifle when I installed the brake but it really wasn't that far off of zero from the standard flash hider.

salt and battery · February 12, 2017, 09:48 AM

sounds like you have a bad barrel comp or not. those are bad groups

mineralman55 · February 12, 2017, 10:58 AM

Sometimes you can get a "bad" one. I originally had a 3-prong flash hider on my 308AR, superb accuracy, modest muzzle climb reduction. I replaced it with another company's full compensator to try it out. Accuracy went down dramatically. The company was good enough to send me another one of their products and I'm satisfied (I have their compensators on other rifles and they work great.)
Stuff happens.

Wyosmith · February 12, 2017, 11:09 AM

It is likely to change POI some, but I'd agree 10" at 50 Yd is extreme.
I am going to bet the threads on the barrel or the comp,(or both) are out of concentric.

It sounds like the bullet it touching the comp inside. Look closely for copper and see if you can tell.

bryanshoot · February 12, 2017, 11:20 AM

I could find no sign of bullet contact in the comp.

P5 Guy · February 12, 2017, 01:04 PM

I wanted to see if the bayonet would change the POI on my SKS. Quite a discussion ensued over whether that was against club rules but the RSO did relent and I shot a ten round group at 50 yards with the blade folded as I had thousands of rounds before. Then folded the bayonet out and locked in place, I swore to the RSO I would not do a bayonet charge when the ammunition in the magazine was exhausted. I sat back on the bench, same hold and was greeted with a group between 6 and 7 inches lower than the blade folded back group.
I was surprised at the difference in the POI.

T. O'Heir · February 12, 2017, 01:28 PM

Your AR have a thin barrel? Adding or removing weight from the end of a whippy barrel will change the POI. Lot of it has to do with how big the compensator/muzzle brake/flash hider is.
"...no sign of bullet contact in the comp..." You know it instantly.

bfoosh006 · February 13, 2017, 01:52 PM

I'm not sure I would blame the comp completely yet.

Make sure your barrel and gas block is not "bonking" the FF tube.... as in not even close to touching.

For that matter... the barrel nut is tight , for sure, right ?

What brand upper and barrel ?

If it was the bullets striking / touching the Comp.... 10 inches at 50yds won't surprise me.

Re zero without the comp.

bryanshoot · February 15, 2017, 07:44 AM

T O'HARA it is not a thin barrel
Bfoosh006 every thing is tight, by ff do you mean free floating handgard? No contact there

February 11, 2017, 09:50 AM	#1
bryanshoot Junior Member Join Date: February 7, 2017 Posts: 6	Compensator changes zero, a lot Hi Bryan here, first time post. I'm a long time shooter-reloader, 40 yrs. Two years ago I got into ar's. 8,000 rds. My latest upper has a 18" stainless barrel rifle gas with comp. Not being happy with accuracy (5moa) I removed comp, accuracy improved but point of impact changed 10" at 50 yds. I'm thinking comp is problem and ordered a new one. My question is should a muzzle device change zero that much? Look forward to joining this forum

February 12, 2017, 02:55 AM	#5
Theohazard Senior Member Join Date: April 19, 2012 Location: Western PA Posts: 3,829	10" at 50 yards is pretty extreme. I'm guessing there's something unusual about that muzzle device. Also, welcome to TFL! __________________ 0331: "Accuracy by volume."

February 12, 2017, 08:18 AM	#6
Targa Senior Member Join Date: March 20, 2014 Posts: 2,084	Yeh that is really extreme. I have a Gamma 5.56 brake on my AR, pretty useless really but I had a store credit. I re-zeroed the rifle when I installed the brake but it really wasn't that far off of zero from the standard flash hider. Last edited by Targa; February 12, 2017 at 08:36 AM.

February 12, 2017, 10:58 AM	#8
mineralman55 Member Join Date: September 29, 2009 Location: deep south Posts: 99	Barrel Comps Sometimes you can get a "bad" one. I originally had a 3-prong flash hider on my 308AR, superb accuracy, modest muzzle climb reduction. I replaced it with another company's full compensator to try it out. Accuracy went down dramatically. The company was good enough to send me another one of their products and I'm satisfied (I have their compensators on other rifles and they work great.) Stuff happens.

February 12, 2017, 01:04 PM	#11
P5 Guy Senior Member Join Date: December 1, 2005 Location: Tampa Bay Posts: 1,804	Harmonic Vibration? I wanted to see if the bayonet would change the POI on my SKS. Quite a discussion ensued over whether that was against club rules but the RSO did relent and I shot a ten round group at 50 yards with the blade folded as I had thousands of rounds before. Then folded the bayonet out and locked in place, I swore to the RSO I would not do a bayonet charge when the ammunition in the magazine was exhausted. I sat back on the bench, same hold and was greeted with a group between 6 and 7 inches lower than the blade folded back group. I was surprised at the difference in the POI.

February 11, 2017, 11:00 AM	#2
Art Eatman Staff in Memoriam Join Date: November 13, 1998 Location: Terlingua, TX; Thomasville, GA Posts: 24,798	All manner of things affect POI. Muzzle brakes, comps, suppressors, muzzle dings, you name it. The amount of change seems to be "luck of the draw".

February 11, 2017, 01:13 PM	#3
Bartholomew Roberts member Join Date: June 12, 2000 Location: Texas and Oklahoma area Posts: 8,462	What Art said. Anytime you add something to the barrel, you change how the barrel vibrates from shot to shot. You don't even need to add something, just lay your barrel against a rest or wall for a quick demonstration of how that changes point of impact. Barrel rigidity seems to help a lot (heavier profiles and shorter barrels) with minimizing that shift; but it happens. Unless you plan on removing the compensator periodically, I'd just rezero and call it good.

February 11, 2017, 03:05 PM	#4
bryanshoot Junior Member Join Date: February 7, 2017 Posts: 6	I expected a little bit, but thought 10" at 50 yds extreem

February 12, 2017, 09:48 AM	#7
salt and battery Junior member Join Date: September 24, 2016 Location: ny Posts: 112	sounds like you have a bad barrel comp or not. those are bad groups

February 12, 2017, 11:09 AM	#9
Wyosmith Senior Member Join Date: December 29, 2010 Location: Shoshoni Wyoming Posts: 2,713	It is likely to change POI some, but I'd agree 10" at 50 Yd is extreme. I am going to bet the threads on the barrel or the comp,(or both) are out of concentric. It sounds like the bullet it touching the comp inside. Look closely for copper and see if you can tell.

February 12, 2017, 11:20 AM	#10
bryanshoot Junior Member Join Date: February 7, 2017 Posts: 6	I could find no sign of bullet contact in the comp.

February 12, 2017, 01:28 PM	#12
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	Your AR have a thin barrel? Adding or removing weight from the end of a whippy barrel will change the POI. Lot of it has to do with how big the compensator/muzzle brake/flash hider is. "...no sign of bullet contact in the comp..." You know it instantly. __________________ Spelling and grammar count!

February 13, 2017, 01:52 PM	#13
bfoosh006 Senior Member Join Date: February 17, 2009 Posts: 1,089	I'm not sure I would blame the comp completely yet. Make sure your barrel and gas block is not "bonking" the FF tube.... as in not even close to touching. For that matter... the barrel nut is tight , for sure, right ? What brand upper and barrel ? If it was the bullets striking / touching the Comp.... 10 inches at 50yds won't surprise me. Re zero without the comp.

February 15, 2017, 07:44 AM	#14
bryanshoot Junior Member Join Date: February 7, 2017 Posts: 6	T O'HARA it is not a thin barrel Bfoosh006 every thing is tight, by ff do you mean free floating handgard? No contact there