VLTOR A5 RE rail lengths: original vs. ?

[DreadPirateMoyer]

In the thread regarding the Magpul fixed carbine stock, Duane mentions (http://m4carbine.net/showpost.php?p=1653112&postcount=40) that the new stock only works on A5 receiver extensions with original rail lengths, not some A5s with longer rail lengths. Does anyone know how to tell the difference?

I asked in the Magpul thread, but got no replies. I figured it was worth bringing up in a new thread since changes in the A5 are probably an individual topic in and of themselves. My concern stems from the fact that I have an A5 tube and a fixed carbine stock on order, and want to know if the tube is compatible.

Thanks everyone. :)

[mtdawg169]

I'm not sure which is the "original" length, but Vltor sells a couple different versions of the A5. I bought the A5SR, which has a shorter rail and works better with stocks like the CTR. It allows the stock to lock up when fully collapsed and I believe it is based on the original AR10 RE.

[DreadPirateMoyer]

That's what I was thinking too: 6 or 7 position. I've got the 7, because I never run my stocks fully collapsed anyway and don't mind some exposed rail, but now I'm scared I'll regret that decision. :\

[mtdawg169]

I haven't been paying attention to the new magpul stocks, so I don't know which one is supposed to work. My A5SR is the same length as the A5, but the rail on the bottom is shorter. I still have some exposed tube when the stock is collapsed, but the adjustment holes line up so that it locks when fully collapsed. As I understand it, the stock adjustment pin would sit inbetween the last two holes on the standard A5 adjustment rail when fully collapsed.

[Todd.K]

The A5SR has the shorter rail, the rail is the same length as a carbine RE. It sounds like you need the A5SR to me.

[DreadPirateMoyer]

Thing is, I don't think the A5SR was the "original" A5, so I don't think Duane would refer to it as such. Plus, if the new stock only fit on the A5SR, I feel like Magpul would specifically state that. What I really think is the standard A5 7-position tube has gone through some sort of iterative development and changed in some way, but that's just inference from Duane's post.

Let me see if I can get him in here...

[SPQR476]

Fits fine with the first A5. The only extension we've found issues with that would require any modifications to the tube are the Larue tubes that have a rail that runs up closer to the castle nut. The FCS is held in place with a cross-clamping screw, so no rail holes are required. It does not engage the rail, just fits in front of where the rail slants up. I haven't personally tried the A5 SR, but looking at it, it should fit. The FCS was specifically designed to work with the original A5 and the AR10 length tubes that were available at the time of design lock as well as standard m4 carbine tubes.

[DreadPirateMoyer]

Ah! Perfect. I completely understand now and realize I misunderstood your post in the other thread.

Thanks a bunch for the help, Duane. Same to Todd and mtdawg.