‘Keyhole-marked’ M4 upper from BCM
Daniel Defense 12" Lite FF Rail
WOA 18" SPR Barrel
Troy F&R BUIS
I used stated torque values when tightening the barrel nut and attaching the rail.
When sighting it in, it required half the available windage to one side, or approximately 12-15 clicks. I’d like to send it to a local gunsmith to have them properly align the barrel. How would they go about doing this, or is this something I can do myself?
I am confused. What makes you think that it isn’t aligned properly? As long as all the parts are within spec and assembled properly then I don’t see the issue. I also don’t think that 12-15 clicks is excessive, though I could be wrong.
12-15 clicks isn’t excessive. However, if you are a little OCD about having your rear sight centered, you could disassemble your rifle and make sure there is no play between the barrel pin and the slot in the upper receiver. If there is play, you could lightly peen the appropriate side of the slot and reassemble. When you peen the slot, make sure you have your barrel in the upper so the upper will be properly supported and you won’t end up making the slot bigger by breaking a corner off!
With an upper receiver that has some radial play between the barrel index pin and receiver slot, I set my barrel indexing using the following procedure;
[b]- Draw a thick black vertical line on a sheet of typing paper. This will be your alignment target.
Tack this alignment target up across from your bench vice where your upper receiver is clamped. Ensure the alignment target is plumbed vertically.
Sight down the upper receiver, adjusting the upper receiver vice clamp and bench vice to position the alignment targets vertical line so that it runs directly through the FSP, FSB, rear sight aperture, and directly through the center line of the bore.
With the help of an assistant, place a non-marring object through the FSB to hold the barrel in position against the direction of barrel nut torque. For this I like to use a large bronze drift.
With the FSB secured and held in place, proceed with the barrel nut tightening procedure IAW the -23&P. [/b]
However in your case your sights are not on your barrel. Your front and rear sights are on your rail and receiver respectively.
Your current windage adjustment is within milspec, however you could double check the alignment of your FF.
VERY GOOD! I wasn’t reading close enough, or it just went right over my head his sights were mounted on a rail. Heck, this might be as simple as shimming the front or rear sight.
12 to 15 clicks? That is roughly 3-4 MOA (assuming .25 MOA clicks) and not excessive. If you 15 clicks is half your available windage, your scope is defective or poorly designed.
I re-checked the number of clicks from center, and it was actually more like 22-23 clicks. I can’t remember if thats still within spec, but like Henny mentioned, I’m slightly OCD. My BCM upper required maybe 1-2 clicks on windage at most, which is a testament to their build quality. I was hoping to reproduce something similar.
I disassembled my upper receiver and checked the play between the barrel pin and slot on the upper receiver. It was almost negligible, so I re-assmebled everything to spec. I will re-zero it in a couple of days and see if anything has changed.
The only other problem I ran into is that I can’t unscrew my Troy rear BUIS from the upper receiver. I used blue loctite on the threads… doh.
Veeref, you should be able to get that blue loctite to loosen up with either a heat gun or putting the tip of a soldering iron on the end of the screw.
handguard mounted BUIS? this doesn’t have anything to do with anything but your handguard- and be glad it’s ONLY off-center by 23 clicks.
take a a mic or caliper to your handguards and measure the distance between the guard and the barrel on either side- if it’s not off by at least .050, i’ll send you a free pmag or something
I use blue Loc-Tite on my screws and am able to break them loose no problem. You might be able to hit it with a hair dryer on max for a couple of minutes, but it shouldn’t be needed once you apply some muscle.
I’ve tried it before and it was A FAIL. With BUIS mounted on a FF rail you’re going to have some adjustment. I always do. You can do a few little things to tinker with it but the bottom line is that the BUIS are just that and that your gas tube and/or barrel nut generally dictates where your rail system locks up. With an optic does it really matter if the rear sight is almost all the way to the right? I know, and it does to me which is why I prefer pinned on front sight towers to a front BUIS. Your shim ends up as thick as the rear sight is off center. With BUIS front and rear you sometimes just have to learn to live with them.
If the width or thickness of the front rail is under spec the front sight may tilt when tightened. I have had that happen with Larue and other clamp on optic mounts on name brand uppers.
