cz muzzle brake changes POI?

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ceilingcat

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I installed a CZ muzzle brake on my 858 tactical -2 and while I used to hit dead on at 100 m shooting 3-4" groups with surplus, with the muzzle brake it was not even on target!! I had to re- sight to get it on paper again, but now the groups are more like 6-7" ? (more random, no 3 shots in small groups within the five groups like it used to do)

anyone have experienced POI change in the horizontal/ loss of accuracy with the attachment of muzzle brakes?

I tried to shim the brake to make it screw tightly, but I suspect this was not good enough.. how do you attach a muzzle brake tightly while allowing for thermal expansion? or reduce/ remove POI changes for that matter?

:redface:
 
I have never experienced this, I can switch between the brake and no brake and it does not change at all. That is on all 4 of my rifles. Mine dont even use a washer. Maybe F the brake from now on then. I only use it on my 7.5" CSA rifle now.


edit: this should really be in the red rifles section
 
Here is what Rick at ATRS wrote on a similar subject.

alberta tactical rifle said:
ANY muzzle attachment can change the POI, but it should not effect accuracy.
IF the gun is capable of shooting 1/2 MOA with no muzzle device, it should be able to retain the same 1/2 MOA accuracy WITH a muzzle device, the POI will likely be different however.
IF a muzzle attachment alters the accuracy there is something definately wrong.

I can speak for all but we have found NO change in accuracy at all with shooting several rifles with and without the Eliminator attached.
Noise, flash and concussion at the muzzle all are different from shooting with or without the device attached.
Click to expand...

This is post #22 of the following thread: http://www.canadiangunnutz.com/forum/showthread.php?t=600034

Hoping this answers your question correctly.
 
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Installing and removing the muzzle brake on my M14 doesn't seem to make an difference in POI; but it's a 2-to-3 MOA rifle on a good day (in my hands).
On my 6.5-'06 the brake did change the POI noticeably; but the groups didn't seem to change in size (with the "well loved" barrel it was a .75 MOA rifle).
On my .221, removing the muzzle device only moves the POI the tiniest bit (about 1/4" at 200m) but noticeably opens the groups (with the FE it'll shoot 10 shot groups of factory ammo into a 1/2 MOA all afternoon; but unscrew it and a _good_ group will just fit into .75 MOA)

So, based on my (very limited) experience, the answer is "maybe." I've never even thought about the "thermal expansion" question, I just make sure that the brake is snug and if required, properly indexed, and leave it alone until it's time to clean.
 
it is indexed, I even put a crush washer on it to make things tight, the indexing is right on because like the ak muzzle there's a pin which fits onto a notch on the brake.

It's the Czech military brake I"m using, I bought it from wolverines.

when I look down the barrel (gun stripped unloaded) I see that the crown and the "crown" of the muzzle brake are not completely true to each other, but way enough to give clearance for the exiting bullet, no bullet scratches etc (I tested with a pencil and actually shot it)

My question is do the escaping gases push the bullets around, analogous to a bad crown, or does the bullet leave before the escaping gases from the muzzle brake, making it not matter?

I'm considering filing down the muzzle brake to fit perfectly with the front sight base without the need for a crush washer Like I see all the other vz's have...
 
ceilingcat said:
it is indexed, I even put a crush washer on it to make things tight, the indexing is right on because like the ak muzzle there's a pin which fits onto a notch on the brake.

It's the Czech military brake I"m using, I bought it from wolverines.

when I look down the barrel (gun stripped unloaded) I see that the crown and the "crown" of the muzzle brake are not completely true to each other, but way enough to give clearance for the exiting bullet, no bullet scratches etc (I tested with a pencil and actually shot it)

My question is do the escaping gases push the bullets around, analogous to a bad crown, or does the bullet leave before the escaping gases from the muzzle brake, making it not matter?

I'm considering filing down the muzzle brake to fit perfectly with the front sight base without the need for a crush washer Like I see all the other vz's have...
Click to expand...

actually shot "it" the rifle, with real rounds, not shooting the pencil out of the bore XD
 
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