Well...bummer

[gatordev]

Thought this was going to be a fun and quick build, but alas... First up, the mock up:



I have a 7" Centurion Arms rail just waiting to go on this, but it looks like the billet upper interferes with the anti-rotation tabs:



Here you can see where one of the tabs is wearing on the receiver:



Other than the barrel and barrel nut, I had all the parts already, so I was hoping to just throw this together, however now I'm worried I'm going to have to invest in a different rail, which makes this become more expensive than I hoped.

Other than grinding down the rail, any ideas on how to fix this? I'm not too keen on doing any metal work on the receiver, either. I'm not even really sure what to look for in a new rail to make sure the same thing doesn't happen.

[Joelski]

That sucks, man. No matter how cool it looks, if it ain't spec, forget it. A midwest rail would fit and not break the bank (again) like that CAA rail. Personally, I'd sack the non-standard upper. Good luck!

[gatordev]

Hmm...I'll have to look at MI.

The story behind the upper (and lower) is a little more complicated. I'd prefer not to just ditch it, lest the wrath of Stick strike.

Also, just for the sake of satisfying my OCD... Centurion Arms most definitely is NOT Command Arms Accessories (CAA). I don't think that's what you meant, but I'd hate for the Google machine to record the error!

[UWone77]

Ran into the same issue when I tried to swap out handguards on an older Mega Arms Billet upper. Couldn't bring myself to cut off the tabs.

[cjd3]

Just how often do billet uppers like this interfere with anti-rotation tabs?

[Tyrannosaur]

Happened to me with a Lantac UAR and that same rail....

[Dstrbdmedic167]

Just how often do billet uppers like this interfere with anti-rotation tabs?

Quite often unfortunately...

[gatordev]

Booooo!

Looking at the MI Gen 2 T-series, it looks like the tabs lock into the included barrel nut, and doesn't go far enough back into the receiver. Anyone see any issues with that? It's interesting to see how much harder it's becoming to get quad rails that don't break the bank and don't weigh the equivalent to a RIS II.

[Dstrbdmedic167]

Not to derail but I assume quad rails that use a standard but are the only thing of interest to you? Fortis makes a great rail that uses a standard nut and works with good amount of billet uppers. Just curious?

[gatordev]

Don't care about the nut other than it not interfering with the upper, but I prefer a lightweight quad rail for this because a) it's light and b) then I don't have to spend more money on some sort of hand stop that's compatible with whatever the attachment mount that's on the rail (though M-Lok has started to win me over after seeing what these guys are doing). I've got a bunch of Larue hand stops stashed away, so sliding one of those on a quad rail solves a problem and doesn't require yet another "thing" to buy.

[UWone77]

Just how often do billet uppers like this interfere with anti-rotation tabs?

Newer uppers have cut outs. Like the Mega, now has a cutout on a revision.

[Former11B]

I was concerned the Anti rotation tabs on my Rainier/Samson rail I ordered several years ago would conflict with the kill switch on my WAR upper. Fortunately, no issues


Can you remove a tiny bit of material from the inside of the tabs so they'll fit around the upper without cutting them completely?

[gatordev]

Can you remove a tiny bit of material from the inside of the tabs so they'll fit around the upper without cutting them completely?

It's kind of tough to tell (I need to get in there with a flash light), but it looks like the tabs would still hit the "shoulder" of the receiver right below where you see the wear mark. The receiver bows out some and I think the bow is slightly wider than the tab ID. But it's worth looking at again.

I may just grab the MI rail and call it good, though. Since the DD MK18 rail is 9.25" and works on a 10.3" barrel, by my math, I believe the MI 9" rail will work on this 10.5" barrel and still give me access to thread on a can.

[Pyzik]

It's kind of tough to tell (I need to get in there with a flash light), but it looks like the tabs would still hit the "shoulder" of the receiver right below where you see the wear mark. The receiver bows out some and I think the bow is slightly wider than the tab ID. But it's worth looking at again.

I may just grab the MI rail and call it good, though. Since the DD MK18 rail is 9.25" and works on a 10.3" barrel, by my math, I believe the MI 9" rail will work on this 10.5" barrel and still give me access to thread on a can.

I say mod the rail and touch up the marks with a little paint and call it a day. It won't take much to remove a little material from the tabs, they are aluminum afterall.

[Former11B]

It's kind of tough to tell (I need to get in there with a flash light), but it looks like the tabs would still hit the "shoulder" of the receiver right below where you see the wear mark. The receiver bows out some and I think the bow is slightly wider than the tab ID. But it's worth looking at again.

I may just grab the MI rail and call it good, though. Since the DD MK18 rail is 9.25" and works on a 10.3" barrel, by my math, I believe the MI 9" rail will work on this 10.5" barrel and still give me access to thread on a can.

I have a 17.5" rail and an 18" barrel and its real close lol