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Affect of muzzle attachment on POI?

910 Views 3 Replies 4 Participants Last post by  gunner69
Does the presence of a muzzle attachment change the point of impact compared to a bare muzzle?

I ask as I just got back to the range from shooting my DPMS .308 and my XCR after removing muzzle attachments.

I removed a 5 slot phantom from the DPMS and an A2 from the XCR. The DPMS shot 2 inches high and slightly right. The wind was 5 mph at 30 degrees to the right so that may have accounted for the slight right shift. The temp was 23 degrees colder from Friday when I shot it with the Phantom. The size of the groups were the same.

The XCR shot 3 inches lower without the A2 from its previous zero.

Any thoughts? I had never shot before and after groups with respect to with and without muzzle attachment and it was suprising to me at how much difference I got.
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Does the presence of a muzzle attachment change the point of impact compared to a bare muzzle?
Anything that disrupts or vectors the escaping gasses asymmetrically at the muzzle will probably have a POI shift, albeit very small. Hence the reason for careful machining on crowns of precision rigs. It would make plenty of sense to notice a POI shift in your scenario. I haven't tried shooting my XCR without a muzzle device, but it wouldn't surprise me if this happened to me as well.
Martens- Here is a message I sent to Aussie Arms a couple of weeks ago. I've ordered a new break for my XCR, and was wondering about it's performance.

My buddy has a 14.5 barrel with a perm. attached break, and I don't know which brand. Anyway, his XCR with Ficochi will shoot an inch or better... I've seen it done.

He also has a Bushmaster Predator in 5.56. It's a 20inch barrel. It's always rated @ .5 moa or better. We've shot it sub moa but are still testing ammo for the right choice. He had a Vortex put on that Bushmaster and his groups went from sub moa to 2" plus. Took us a while to figure out what was up. We took off the Vortex and low and behold sub moa. Put it back on, and 2 inch groups.

Anyway my point in all of this is that I wonder if my SBR will shoot better with that new break on it. Maybe the Vortex doesn't hurt the XCR, maybe on the Bushmaster it's an issue of harmonics and shouldn't even have a flash hider (it doesn't come with one nor is it threaded for one). Anyway, it's just a thought. My SBR seems to shoot fine but I've always had that Vortex on there except for when I first got it. And I broke it in on a CQB range, so there was no precision involved.
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Surprise..... yes different muzzle/flash hiders/brakes will make a difference. That's why you try different products til you find one you like, that shoots acceptable. Also keep in mind different (yes, in the same caliber) barrels may like one manufacture (or hand load), or bullet weight better than another. Confusing? Yup, but thats the fun of it all. One of my hunting friend uses one load only. He weights the case, bullet, powder charge, and uses one specific primer for his favorite load. All the rest are practice. Shoots GREAT groups and seems to get more "one shoot" game than most. Myself, I don't go that extreme, nor recomend it. But raise your ass too far up, at 500 meters, and I WILL put a new crease in it. :toast:
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