VTAC Rail Issue, or iron sights? Updated w/ SOLUTION

[Gunzilla]

GOT ZERO!

Looks like the backing for the attachment rail was hitting the gas block and that is what was screwing up my ability to get an iron sight zero.

I simply cut the rail backing and remounted the rail in the same place and there was a noticeable difference in where the barrel protruded out the handguard. I knew at that point I found, and solved, my issue.

Zeroing at the range was a snap, considering I wasn't wearing my eye glasses, and by the time I was done I was tagging the square steel targets at the 200 & 300 yard ranges with almost every shot.

I knew I would learn something from getting my first free float hand guard, I just didn't know it would be so soon.......and that it would require a hachsaw.

Thanks again to all those that took time to comment.

[rero360]

I have the exact same set up, factory front sight post though, and I too noticed that the mounting hardware touched the gas block, very minimal on mine, say a few thou, so I took mine out and hit it with a file to take off a bit of material. I can now see daylight between the two so it never became an issue for me and just had to bring my front sight down two clicks to get on steel at 200 meters.

I would say its probably just an issue of tolerance stacking, if they were to make the mounting hardware thingy under the rail say .05 shorter on each end, it would eliminate the chance of this problem happening.

Glad to hear you got it resolved though.

[ache_d]

Bad thing about problems is that they are problems. Good thing is that you usually aren't the first. And in this particular instance, I had that problem.

* Glad you got it to zero, so did I with my original, but I didn't have much faith in it. *

Same deal, 13" vtac, with DD front sights. I had that sight cranked down to it's max! There is a fix to this, though it may not be what you wanna hear.

1. Sell that, with the nut it came with and rail sections on TOS or anywhere!!

2. If you love the lightweight and "customization-ability" of the rail... buy it again............BUT in the new alpha config. It uses the standard barrel nut. (and actually I was thinking about taking a pic and making this a thread, still might)

3. Mount it up! Very easily I might add. and go shoot the hell out of it!!



I have a had a good bit of field use/range time with troy and vtac for that matter and got the original vtac/troy rail when it came up and I about went insane trying to get my rail to 180 deg instead of the tilt, something like 178 deg since it is so long it is noticeable.

The alpha is rock solid and damn near idiot proof when tuning it in. You do have to slightly rotate each allan slowly in sequence but that is easy.

In my opinion the pinch style of mounting is DEAD! Troy got it right this time!

I'll maybe make this a thread sometime later, if y'all think it would be helpful, when I get to my work comp.

[Gunzilla]

Ache_d,

I think you should make your new thread, I'd like to see how it works out, it does sound like a nice set up.

This being my first free float hand guard I really didn't have the extra $$$ to sink into a high end HG at this time, but may want to upgrade later if the VTAC HG fails to stay in place.

I did take more care in remounting the HG so it's not too tight. In fact I installed the long end of the allen into the cap screw and used the short end of the allen as my leverage to tighten the cap screws...using blue locktite to secure them. For now I'm confident, but maybe that's just my enthusiasm coming through after getting this figured out.....either way I'm feeling a lot better now than I was a week ago.

[Nightvisionary]

GOT ZERO!

Looks like the backing for the attachment rail was hitting the gas block and that is what was screwing up my ability to get an iron sight zero.

I simply cut the rail backing and remounted the rail in the same place and there was a noticeable difference in where the barrel protruded out the handguard. I knew at that point I found, and solved, my issue.

Zeroing at the range was a snap, considering I wasn't wearing my eye glasses, and by the time I was done I was tagging the square steel targets at the 200 & 300 yard ranges with almost every shot.

I knew I would learn something from getting my first free float hand guard, I just didn't know it would be so soon.......and that it would require a hachsaw.

Thanks again to all those that took time to comment.

Wow it's hard to believe BCM would ship something that has an obvious design flaw. You as the purchaser should not have to use a hacksaw on a BCM product. That takes BCM down a notch in my book.

[rero360]

Wow it's hard to believe BCM would ship something that has an obvious design flaw. You as the purchaser should not have to use a hacksaw on a BCM product. That takes BCM down a notch in my book.

I disagree, its not a design flaw, what we are seeing is tolerance stacking when assembling parts from different manufacturers, the Troy V-TAC rail and mounting hardware, BCM barrel with what looks like a Yankee Hill or Stag low pro gas block. I mean what I saw on mine was maybe .01" of interference if that, probably just the thickness of the anodizing.

Overall its still better than some of the clearance and other tolerance issues I deal with at work when we get parts in from our other shop in Michigan.

[MSteele]

I don't think BCM should take on the blame as this seems to be a pretty common issue with longer Troy/VTAC rails. I know that if it was sent back to BCM they would have fixed it or resolved the issue. Even the best companies in the world at times have issues with products or services. The most important thing is what they do to correct the problem with the customer and also internally. Whenever there is a high demand for a company's products and they are maxed out it is understandable that a small percentage of QC issues will occur. Even if it's their manufacturing process or assembly with other manufacturers parts.
BTW good job figuring out the problem and fixing it. These types of things always help out in the long run when trying to diagnose other issues.

[ZoneOne]

GOT ZERO!

Looks like the backing for the attachment rail was hitting the gas block and that is what was screwing up my ability to get an iron sight zero.

I simply cut the rail backing and remounted the rail in the same place and there was a noticeable difference in where the barrel protruded out the handguard. I knew at that point I found, and solved, my issue.

Zeroing at the range was a snap, considering I wasn't wearing my eye glasses, and by the time I was done I was tagging the square steel targets at the 200 & 300 yard ranges with almost every shot.

I knew I would learn something from getting my first free float hand guard, I just didn't know it would be so soon.......and that it would require a hachsaw.

Thanks again to all those that took time to comment.

Care to post a pic on how you cut the rail backings? Or did you simply chop them in half ?

I'm running into a similar issue though I haven't seen it have any negative effects yet. I moved my rail from the original position (far forward) a little further back about 4 inches from the end. (I don't have super long arms)

I noticed while cleaning my weapon that the rail backing was in direct contact with the gas block. I'm not 100% knowledgeable on the subject but I would assume it would influence the harmonics of the barrel. I took a dremel to the screws as one was fully in contact but it still seems to be a little too close for comfort.

I've debated shaving the entire backing down to make it thin - or just not using it all.

But I love my Troy stubby vertical grip.

[Gunzilla]

Wow it's hard to believe BCM would ship something that has an obvious design flaw. You as the purchaser should not have to use a hacksaw on a BCM product. That takes BCM down a notch in my book.

Don't over-react yet, the rail was mounted midway down the bottom of the hand guard when I got it from BCM, I moved it to the end so I could mount a bipod before shooting it. I obviously missed the contact point when putting it back together.

Turns out this was my mistake for not noticing the contact with the gas block and the rail backing, and hand nothing to do with BCM's assembly process. (Funny thing is I had it all boxed up and ready to ship it back when I thought to check the gas block area as a last resort)

This is my second BCM upper, so far, and that's all I'll spend my money on in the future. Not only do you get a nice product but the service is there and ready to help. They were very prompt when I was contacting them on this issue.

Zone one, I simply cut about 3/4" from between the mounting holes, held the small piece that goes farther in with a extendable magnet and got the screw started, then held the backing piece that is closer to the end with my finger until I got the screw threads started.

The backing piece that is closer to the end is turned so the longer part is towards to end of the tube so the rail still has most of it's original strength, and leaves a big enough gap to accommodate the gas block.....it worked out rather nicely.

I thought about grinding the backing piece thinner in the middle but that would have been a longer process. By the looks of the final result (it's hard to get a good picture of it) the piece would have needed a lot of grinding, it was much easier to cut out the middle section.

FYI: This can be done by making only 1 cut but you'll have to turn the ends of the backing piece so they point away from each other, to make room for the gas block.

[rero360]

I moved mine forward one slot, so one back from the one Gunzilla mounted his at, so I just took a few thousands off the leading edge of the backer, opposed to cutting the sucker in half. Either way, not a big deal and easy enough solution to adapt the system to your needs.