[PDUNN0806]

I took my ACR to the range today to dial in my EOTech 553 w/ 3x magnifier. i noticed when shooting cold bore i could dial the site in on point. but when it got warm the point of impact would shift left a couple of inches @ 100 yards. i fould myself adjusting back and forth. is this normal? i just found it hard to get it dialed in when my POI was shifting as i was shooting. any comments or suggestions for getting my optic dialed in, please let me know.

 

[bigdog2003_99]

is your barrel completely tight? mine was past the 90 degree point by a couple of clicks i'd start there, mine held zero pretty well cold or warm

 

[cjt50]

is your barrel completely tight? mine was past the 90 degree point by a couple of clicks i'd start there, mine held zero pretty well cold or warm

+1: Make sure your barrel is nice and tight.

When I 1st got my rifle, I noticed the same thing. Barrel wrench was at 6'oclock. I tugged on it getting 2 more clicks out of it and it has held zero perfectly since then.

 

[PDUNN0806]

after the first time i shot mine i pulled it apart and cleaned everything. i also tightened my past 6 o'clock until i got a possitive stop. It could have just been my aim. at 100 yards even with a 3x mag the targets were still pretty small. but it was a pattern of shifting. cold it would hit pretty much right on the money, but after about 10 shots a second apart it would shift left by a couple inches. maybe next time out i will try at 50 yards so that i know i am on point when aiming and see what happens.

 

[DSM]

Some of the early ACR's had barrels that sat off-center in the receiver too. (Mine was one of them...) It wasn't so much of a shifting zero as much as it was just way left, but, there could be some kind of bias in the trunnion, extension, or socket threads that is presenting itself as the metal heats up.

How does it look with the handguard removed?

 

[bomjoon]

Mine hangs a little to left when I tighten it.

also i noticed when the barrel is not fully tighten I would have Failure to extract sometimes.

 

[DSM]

Mine hangs a little to left when I tighten it.

also i noticed when the barrel is not fully tighten I would have Failure to extract sometimes.

Bushmaster knows about the canted barrel problem on some of their rifles so they should be able to fix that in short order. Though with the factory shutdown and move it might also be worthwhile to wait a little longer to let them catch back up.

 

[PDUNN0806]

it looks fine with the handguard off. it only seems to shift a couple inches after it warms up