Troy Vtac XTR Rail Alignment Issues

AR/M4 Custom Build Forum
1

I don’t know if any of you have had this particular problem/issue arise during an installation of the new Troy Vtac XTR FF tube but this is what happened to me.

I recently purchased a BCM 14.5" LW middy w/ the Troy Vtac ff tube.

Mounted it to my LMT lower with the LMT NM trigger and off to the range for some bang bang goodness.

Great right? NOT!!!

Couldnt align my irons for love or money… the weapon didn’t just climb right it JUMPED. Very uncomfortable to fire and insanely frustrating to shoot.

I fired 68gr OTBT Match Winchester, 62 gr Lake City, 60 gr Hornady Tactical…

nada… nothing worked. Group looked like a shotgun pattern not a rifle group.

I should have had a clue when my irons wouldn’t zero at 25 yrds unless I cranked it ALL the way down into the sight body. (CLUE #1!)

Well, I’m thinkin… “maybe the tube is loose.” Nope, solid as a rock.
Out of alignment?

YEP!!!

Took an steel engineer’s rule that lives on my drafting table and checked the upper reciever/FF tube. It had a shallow but noticeable declination towards the receiver. It was off true by only 1.2 mm. but that was enough to through everything else out of wack.

Loosened up the tube (went to the website and found the install directions first thanks) and using a set of shims left over from a PWS 556 install reseated it and placed two (2) peal washer shims from the pws brake kit between the upper receiver and the tube.Tightened it back up.(Finger tight… not too much, not too little)

Checked it with a torque wrench and I was on the money at 58 ftlbs.

With much trepidation I returned to the range today and…

Guess what? Straight back recoil… not “hooked” like before.

Groups are groups again!!!

The moral of this story is that like Irangunz and other have stated and stated again…

The AR-15 is the SUM of ALL it’s parts.

So simple a fix… so frustrating a problem

Hope this doesn’t happen to anyone else but here’s the fix.

2

I’ve installed more than a couple Troy and Troy/VTAC tubes. With some uppers the rail and the uppers rail will not align when the barrel nut is aligned perfectly for gas tube straightness. The only fix I’ve seen is using another upper receiver or just not using a rail mounted front sight. YMMV.

3

In this case I didn’t have to leave the shims in place. I just used them as spacers during the tightening process.

If I found that I would have had to have them there full time I probably would pull the gas tube and slip a shim over it to act as a full time spacer between the tube and the upper receiver.

I’m hoping that this was THE fix and not the start of chronic tube alignment issues.

Thanks for all the input and information over the last year GotM4.

Always learn lots from you and Irangunz

4

The Brownells rail alignment tool does help with many of them as well. I use this as well as lots of blue loc-tite on the two bottom screws. The alignment tool can be adjusted to pull the rail up to equal the height of the receiver. Most of the time the side to side alignment is okay but not always.

5

Grin,

GMTA and all that… I wanted to order one of those tools but Brownell’s has been sold out/backordered on them for over a month.

Guess I’ll just have to wait to get one for myself.

Too date my alignment tool has been a removable carry handle from my old patrol rifle. It works reasonably well … granted it’s not perfect but it does get you in the neighborhood.

Untill I do get the proper tool for this job I’ll just have to Rube Goldberg my way through it.