Proper length for free float handguard

[Dos Perros]

I'm building a 6.5 Grendel with Lilja's AR740 barrel and I'm having trouble deciding which handguard to get. The rifle will be fired mostly off a bipod from either a bench (paper), prone (paper and pdogs), or with shooting sticks for coyotes and deer. The gas system for that barrel is rifle length, here's a link to the drawing:

http://www.riflebarrels.com/products/pdf_barrel_drawings/ar_profiles/ar740.PDF

From the front of the upper receiver to the beginning of the gas block section is about 12.1 inches. I see that Midwest Industries offers it's Gen2 SS One-Piece FF in both 12" and 15". So the 12" version will stop just short of the gas block, and the 15" version will completely cover it. Is one preferred over the other? Why?

I am planning on an adjustable gas block, so perhaps exposing it would make adjustments easier, however I'm not opposed to buying the 15" version and using a drill press to put a hole in the handguard for easy gas block adjustments (it uses an allen wrench). Thoughts? Thanks for the advice, folks.

 

[ORD]

I wouldn't get too caught up on the length. Provided you get AT LEAST a rifle-length handguard (~12" or so on a basic AR-15) and your gas tube is covered, that's all that matters. The nice thing about the extended lengths is that they allow you to get your bipod further out toward the muzzle which in turn makes for a more stable shooting platform.

If you do opt for an extended length handguard, there are a variety of front-adjustable gas blocks on the market that make it easier to run handguards that completely cover the journal/block and DO NOT require you to hack up an expensive handguard system. The one thing with the MI series handguards you are looking at though is that they are VERY small in terms of the ID (only ~1.3" or so if memory serves) which may not permit you to run an extended length handguard unless you are running a very low profile gas block. You'll need to take careful measurements to ensure that any adjustable block you get will fit under the MI. Have a look at the new Sentry blocks from SLR Rifleworks, as well as the Gen2 blocks from Syrac. Both are about as low profile as you'll find for an adjustable block and both are front adjustable so no drilling out/milling your expensive handguard so you can adjust the block when needed.