Issue zeroing Bushmaster M4 A3 Type Carbine

[SnakeEye]

As the title describes, i have a Bushmaster M4 A3 Type Carbine outiftted with an A.R.M.S. #40 Stand Alone Flip up Rear Sight.

I have been able to get the elevation perfect, but i am having a problem centering it.
The rear sight is pushed all the way to the right as far as it will travel, but my rounds are still hitting several inches left of center at 50 yards.
Does anyone know what could be the cause of this?
thanks all

 

[Lugnut]

If your rear sight is all the way to the right and you're doing everything correctly you need your barrel reindexed. I have a Bushmaster M4A3 that needed reindexing as well. Call Bushmaster they will do it for you. I don't think it's something you can do by yourself. Mine wasn't even as bad as what you describe and I sent it back. FWIW they were very quick. Good luck.

 

[C-pher]

That's good to know. I have one that's doing the same thing...

I was going to wait and have Derek look at it sometime.. But maybe I just need to send it back.

 

[SnakeEye]

im getting the same feedback from the ar15.com forums.
looks like my rifle is going away for a little while.

 

[BoB13]

Maybe there is a fellow AR owner on the forum near where you live who has the tools needed and could help you out rather than send it away with the time and shipping costs. Or a local gunsmith. I'd help you out but I'm a ways away.

 

[Lugnut]

Snake- call Bushmaster first. You only have to ship the upper so it doesn't have to go via FedEx overnight or anything because it's not a firearm. If you wanted to go on a field trip they are not to far up in Maine... not sure if they take drop offs. FWIW with mine, when I zeroed it in the rear sight wasn't quite to the far right but close. I was using the stock BM sights.

 

[Mattitude]

This is actually a pretty common occurance. What happens is when the front sight A-frame/gas block assembly is installed on the barrel it is then drilled through and the taper pins installed. The pin "holes" aren't pre-drilled on the barrels. Sometimes it can be an easy fix if the grouping isn't much far off. Drift out the pins and knock the A-frame in the direction of the grouping...if it's shooting left, move the assembly left. It doesn't take much at all. Then drive the pins back in. They only go in/out in 1 direction, so just be sure which way they came off. If you want to eliminate the whole problem all together, just get a power wedge front sight assembly from www.fulton-armory.com for 60.00 It's a USGI front sight block that uses 4 set screws where the taper pins go through. That way you can center your rear sight and then adjust the windage with your front sight. Tighten set screws and you are set.

 

[SnakeEye]

i shot off am email to tech support at bushmaster yesterday and im hoping for a RMA number or something within the next day or so.
considering that my sight is over-travelled completely right and im still 4 inches left at a mere 50 yards id say its a little more than i want to play with. At 100 yds or more its even more exascerbated.
I want it fixed correctly, so im willing to take the time to wait to have it fixed by the people who broke it in the first place.
hopefully as it was a private purchase by me, it wont hurt me much in the wallet.

 

[Lugnut]

Snake-

Why not just call Customer Service: 1-800-883-6229 Mon. through Fri. 8:30 am - 6:00 pm? It might speed things up for you.

 

[SnakeEye]

okay i called and got an RMA number. I stutter a little so i tend to avoid the phone as much as possible, but i want my damn rifle working.
I ship out the barrelled upper reciever tomorrow UPS ground. Hopefully it wont take a dogs life.