Unable to secure a Troy Alpha rail

[kidicarus13]

I have a barrel that doesn't have the what I consider the standard shoulder taper on it. (Pic #1 below compared to barrels #2 and #3) I am trying to use a Troy Alpha rail with my barrel but the three screws that are used to secure the rail to the barrel do not contact the barrel because the shoulder is not long enough. Any suggestions besides using different rail? Is there a collar or something I can secure to the barrel?

59048

59049

[kwando]

Maybe I'm wrong but I thought those locking "lugs" locked onto the barrel nut.

[SouthPaw]

The three screws and 'holders' attarch to the barrel nut, not barrel. They go at the back side of the rail closest to the upper receiver. Most barrel nuts fit the rail just fine but I have run into a few that didn't quite fit. At that point you have three options, grind/file down the teeth of the bbl nut, force it, or find a new bbl nut. Personally I would go with option three from experience.

[kidicarus13]

I'll have to look at it again tonight and repost with pictures. Thanks.

[SouthPaw]

http://www.m4carbine.net/showthread.php?103591-Troy-Alpha-Rail-Install-and-Review

http://youtu.be/mfYpR6TLEMI

This should get you pointed in the right direction. The first one I put on was a little confusing but it's just like assembling a stripped lower. Once you have you done it the first time, it's a breeze afterwards. I think I have put a total of five on over the last year or so.

[Great-Kazoo]

The three screws and 'holders' attarch to the barrel nut, not barrel. They go at the back side of the rail closest to the upper receiver. Most barrel nuts fit the rail just fine but I have run into a few that didn't quite fit. At that point you have three options, grind/file down the teeth of the bbl nut, force it, or find a new bbl nut. Personally I would go with option three from experience.

There's option #4. Is used if you're unable to index the nut correctly. Plus it squares the receiver to bbl extension fit.
http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/receiver-tools/ar-15-m16-upper-receiver-lapping-tool-prod20220.aspx

[kidicarus13]

I got home and played with the rail/barrel/upper and now that it makes sense to me, I feel stupid for asking about it. Seems to lock up tight now that I understand how it secures. Thanks to all that replied.

[kidicarus13]

Dupe... sorry, new version of Tapatalk

[kidicarus13]

Dupe

[SouthPaw]

If you swing up north, I have you covered.

[YammyMonkey]

With the Alpha rails you cannot grind down a tooth on the barrel nut if you're having gas tube alignment issues. The nut needs to be in the proper position or the rail will come loose during shooting.