Clearance Needed Between Gas Block and Free Float Rail

[GlockenSpiel]

I have a Midwest Industries M-Lok rail with a Criterion Hbar barrel, and an aero low-profile gas block. The bottom of the gas block is pretty close to the inside of the rail. I don't have feeler gauges, but I measured it with a 13pt piece of cardstock, and two of those fit so it is at least .026 inches of clearance. I can squeeze the barrel and handguard together, but it takes a fair amount of force, as the barrel and handguard are both pretty stiff.

I do not see any signs of stringing or accuracy issues. I shoot with a sling a lot but I am not planning on getting a bipod or anything. Everything is all aligned and screwed and pinned together at this point, so I would rather not have to take it apart and find an ultra-low profile gas block for it. Should I worry or just drive on?

[drummer]

That's awful close. I would look for another rail or smaller gas block.

I haven't used any MI rails, but if you do any bipod, barricade stop, or sling shooting, the rail may flex enough to contact the gas block and hurt accuracy.

Also, if you end up putting any MLok pieces near the gas block, the retaining nuts may touch the gas block.

[OlongJohnson]

Look in the quality tools thread for angle grinder recommendations if you don't have one already.

[Rick R]

Some of the MI “Slimline” rails don’t leave much clearance but feel really good. I have a couple and haven’t had any issues with normal use. Sure you might cause interference with techniques that put a lot of torque on the rail but what percentage of your shooting requires that kind of sideways pressure?

Before you break out the grinder you might call MI and see if another rail is compatible with your barrel nut. If so sell off the used rail with the new nut.