another compensator question

[dennisp5]

I am wondering if anyone is getting a POI change when they install a comp. I know this can happen on rifles, but does it happen with a 9mm.  I put a cheap e-bay single port comp on my 16" PSA  barrel and it shoots a little low and right now, but I have a cheaper Primary Arms red dot (can you tell I am cheap?) that might be failing, so I am curios about POI shift with the comp.

Thanks

Dennis

[Xanatos903]

I think I did have to rezero after putting my comp on. It doesn't seem like much at the ranges we shoot, but you'd probably see drastic shifts in zero at 100 yards just with the addition or removal of a comp. 

 

If you're having problems with a Primary Arms optic, send them a message (info@primaryarms.com). I've sent two of their microdots for service after years of use, and they fixed them free of charge. 

[Steve RA]

In my experience any change regarding the barrel can affect the accuracy/POI.  Sight it in again with the comp installed and see if the accuracy - group size - changes.

[Aircooled6racer]

Hello: One thing to check is to make sure the bullet is not hitting the comp. Look for marks on the baffles. Some barrels are not threaded concentrically with the bore. Thanks, Eric

[Flatland Shooter]

I finally got a PCC barrel that gives me decent groups at 100 yards.  It still has the birdcage on it.   

 

Until I decide I really need a comp (hard to justify on a 9mm PCC) I'm not messing with it.

 

A change in POI I can fix.  Bigger groups I can't. 

[dennisp5]

I haven’t shot this gun past 25 yards but the groups didn’t change, just moved. I re zeroed and it seems fine. I was just kind of surprised to see the POI shift at close range. 

Dennis

[BartCarter]

FWIW, I drilled and squared a 6 inch AL piece of round stock for a friend so he could have a linear comp. He tapped the threads off center and after we zeroed at 10 yards, was off the paper at a 25-yard confirmation.

 

I enlarged the bore and re-taped it for him. That fixed it. I am thinking that when the bullet exited, the bullet was close to one side and actually put a curve on the flight path. Who would have thought that could have happened?

[MikieM]

I think that's called the Bernooly effect. Like when two ships get too close they suck into each other. 

I'm almost certain that's right.

[Steve RA]

Bernoulli's principle