I took my grendel AR out to an F Class match yesterday and it was all over the place at 1,000.  The day before the match (this was my first) I found out about the no brake thing and took it off and put a thread protector on.  My question is: Did the loads I developed with the brake on become mostly useless when I took the brake off?

I need to pull out the magneeto since I have a bunch of these rounds left and see if it affected my ES or if maybe I messed something up in the reloading process.

Wind was also pretty brutal, but that is a whole different story.

everything matters and especially at 1000 yards and especially with a marginal caliber for that distance like Grendel. So pretty much as you found out your data was a no go after the barrel change .

Yeah I stopped after firing a few sighters and scoring 11 shots. Wind was 15-35mph half value so I was really hoping that would be my only challenge. Once I had a round hit  low and a round hit high while my position felt good I knew I was just wasting ammo.

I'll throw the comp back on and use that rifle for other things... Time to rebarrel a bolt gun for the next match I fit into the schedule.

with that kind of wind and the Grendel slowing down to barely supersonic at 1000 the wind would be all over it plus you would need a new zero without the comp.  F class shooting requires a special gun just for that.  All the other fancy big $ tactical guns must stay home in the safe.  Don' task me how I know.

when i put a brake on my 308 it moved the POI something like 3mils at 100 yards, so while it might not change the load, it does certainly affect the barrel harmonics.

Sounds like your velocity dropped to transonic and your bullets lost stability. Need more velocity, not to remove a brake. A good brake has virtually no discernible impact on accuracy or stability.

I expect a POI shift with a muzzle device but 3 mils is a lot.

the short answer is yes: you will experience a POI shift with ANY change of your muzzle device.  I get POI shift if my thread protector backs out a few threads if I don't snug it down tight.


that being said,  occasionally you'll luck into a gun that doesn't shift much, or at all with a thread protector or muzzle break.  I think I've had 2 that weren't real sensitive to it.


1 of them shot to same POI with my can on and off.  complete and utter stroke of luck.  It was sensitive to how I put the can on though, I had to put it on the same way every time to keep it from shifting, but once I got it down it was repeatable.