I recently bought a lightly used (less than 500 rds) Bushmaster AR15 (XM15, A1, 20" BBL) from an old fella locally.
Anyways the appperatures on the rear flip sights on the fixed carry handle upper are both mighty small.
I have it in my head to change to the type like the one that came on my RRA. One side of the flip is small and the other is a much bigger diameter apperature.
So my questions are:
Is this a good idea?
Is it easily done? Seems like it is.
If possible, what/ which do you recommend I get to replace the stock one from Bushmaster?
If this topic is located on the forum please just point me there.
The rear sight can be somewhat tricky to disassemble & reassemble but not something to be afraid of. Just look online for instructional videos or if your not comfortable doing that just run it to a local gunsmith. but…
…before you change anything out look at the existing sight and make sure he doesnt have a screw in aperture in the large apeture hole. Some service rifle shooters screw them in to help there focus (old eyes for me). It usuakky has a lens in it.
You may want to try some gun show parts suppliers. I’m not really sure though. As an armorer I tend to order my parts right from colt, and the aperture L is not something I’ve ever ordered.
If I recall correctly one of the apertures on an A1 is supposed to be for longer range use, often indicated with an L.
You could simply drill the other one out. Sounds low tech, but if you keep it concentric and hit it with some alumiblack, should be fine. If you muck it up you can replace it.
Replacing the A1-type rear with an A2-type is pretty common and relatively simple. Here’s a video from Brownells that shows what’s involved in the process: http://www.brownells.com/.aspx/lid=11433/learn/
The only problem you may run into is that the A2 is slightly wider than the A1 qnd you will lose some windage adjustment. It’s usually not a problem, but some rifles have canted fsb or sloppy barrel pin slot and need extra adjustment to get zero’d.
Changing out the parts shouldn’t be too bad. I’ve done it before.
You’ll need to drive out the roll pin on the windage drum on the right side. I put some masking tape on my roll pin punch to know when I had driven the pin out far enough to remove the drum but not so much that I drove the pin completely out.
Use some care when removing the windage drum, or the detent could pop out under spring pressure.
After that, unscrew the windage screw until you’ve unscrewed the sight. Install the new sight (here, the flat spring may give you some fits with lining up the windage screw properly for the windage drum), and reverse the process.
