I was literally laying in bed tonight trying to get to sleep thinking about nothing in particular when I had a nightmarish revelation. Here's the background... I'm having a 6.5 BPC barrel made by the gentlemen at Ballistic Advantage. Its a 13.5" barrel that will have a permanently attached compensator bringing it to 16". Because they have to mount the compensator I went ahead and sent them a low profile gas block to mount first, (because, of course, once the comp is on the gas block wont fit around it).
My plan was to mount this in a Spikes SAR rail. What occured to me last night was that the barrel nut for the SAR might also have to be put on the barrel before the gas block and the comp. It's a BattleComp BA and a Vltor low profile gas block. Can anybody tell me if the barrel nut will fit past these or do I need to get a SAR barrel nut ASAP to Ballistic Advantage. The barrel is supposed to be done around mid March (in about 2 weeks).
The Vltor gas block appears to be .925" in overall width and the BA BattleComp is .900" diameter.
Thanks for any help anybody can give me!

I'll let the Spike's guys make the final call here, but I'm 99% certain that the SAR barrel nut (or any barrel nut for that matter) won't go over the comp and gas block.

I would second that assumption but am not 100% sure either; based on reading I did today on the installation of the SAR rail, step 1 was remove the gas block, compensator, etc. I'll see of I can find that post...

ETA linky:
http://www.weaponevolution.com/forum/showthread.php?t=3059

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neoexodus2, on Flickr

That is correct.

The barrel nut would clear the BC, but wouldn't clear the gas block. And the gas block you have to put on because it won't clear the muzzle device.

Before pinning, make sure you have finalized the decision of which gas block and rail you will be using, because the block and nut will become semi-permanent fixtures of your barrel once you pin a device on it.