KMR compatible gas blocks

**BoilerUp** · 11 February 2016, 20:32

For those of you running a KMR, please post what gas block you are running underneath the rail and if you had any clearance issues.

I ask because I swapped handguards for a 15" KMR-A over an 18" WOA SPR w/ Geissele Super Gas Block and it only takes a tiny bit of deflection for the rail to touch the bottom of the gas block. This is also after grinding down the "ears" that guide the cross pin. So, I'm going to have to swap out gas blocks. But, my WOA is a bit thick at the gas journal so fitting the gas block was a bit of work to begin with. I'm thinking about trying one of the oversize Black River Tactical or perhaps an SLR clamp-on.

Obviously the BCM lo-pro works, but I'd like to hear what else has been successful for the Illuminati.

**Josh S.** · 11 February 2016, 20:58

No personal experience here but I got curious and googled it. A lot of people seem to be running SLR Sentries underneath their KMR's. Apparently SLR has two series of gas blocks and the Sentry is the smaller of the two.

**Aragorn** · 11 February 2016, 21:04

Originally Posted by Josh S.

No personal experience here but I got curious and googled it. A lot of people seem to be running SLR Sentries underneath their KMR's. Apparently SLR has two series of gas blocks and the Sentry is the smaller of the two.

That's what I'm using under mine...

**alamo5000** · 11 February 2016, 21:16

I've never used the KMR but my google fu tells me that the ID is the same as the SLR rails.

I use SLR adjustable blocks now, but before I was using Rainier Arms Low Profile gas block. If you're not interested in anything adjustable that is one choice.

The RA block was physically longer by quite a bit vs the SLR blocks. That shortening of the length solves some of the M Lok conflicts (but not all).

I am guessing the KMR only comes in keymod though which I have zero experience with.

**Farva** · 11 February 2016, 21:42

I would also assume BCM's gas blocks would work under the KMR

Edit: it would help if I read all of the OP's post

**BoilerUp** · 12 February 2016, 06:11

Originally Posted by Aragorn

That's what I'm using under mine...

Are you running the set-screw or clamp on?

**Jerry R** · 12 February 2016, 06:33

I have two KMR rails. I used Syrac Ordnance Low Pro Adjustable under both - no issue. They are both pinned. Large pic below, you can see the Syrac in the upper left corner. Click it twice and you can see the fitment.

**EO3** · 12 February 2016, 06:49

Not sure if you want clamp, set screw, adjustable, or what, but I know the Faxon micro gas block is very small as well and comes in at a good price point if that matters to you.

**RiverRat** · 12 February 2016, 08:30

Factory-pinned Daniel Defense (0.625") under mine with plenty of clearance on all sides.

The Syrac and SLR Sentry work. Jerry showed us the Syrac and the dimensional drawing for the SLR is below:

Image credit: SLR Rifleworks, externally referenced from their product information page.

BCM reported that the Vltor clamp-on will fit if you want non-adjustable.

The Daniel Defense clamped version has been reported as no-go with the KMR.

**Aragorn** · 12 February 2016, 10:22

Originally Posted by BoilerUp

Are you running the set-screw or clamp on?

Set screw.

**mtdawg169** · 12 February 2016, 17:37

BCM, Vltor, Noveske, etc

**BoilerUp** · 13 February 2016, 17:10

Thanks to those that posted, especially those add their direct experience. I took advantage of the sale at SLR and ordered two Sentry 7 gas blocks. One clamp on and one set screw. Besides by 18" WOA SPR barrel, by ARP 6.8 could stand to have the gas system dialed back a bit. I'll report back later on how they work out.

**alamo5000** · 13 February 2016, 17:31

I will add that the dimpling of the barrel will be crucial no matter which block you use. (of course I am talking about set screw types) One of my barrels seems to have the dimpling 1 or 2mm off and it makes for some minor contact with a rail with a really slim interior. The clamp on one would probably fix that issue. On my other barrel Todd at SLR actually dimpled it for me with the jigs they have at their shop and the fit is perfect.

**cjd3** · 13 February 2016, 20:26

Originally Posted by BoilerUp

Thanks to those that posted, especially those add their direct experience. I took advantage of the sale at SLR and ordered two Sentry 7 gas blocks. One clamp on and one set screw. Besides by 18" WOA SPR barrel, by ARP 6.8 could stand to have the gas system dialed back a bit. I'll report back later on how they work out.

It seems like we're building clones. I just put a Sentry clamp on my WOA SPR, which lies under a 13" EMR, that will be shortly upgraded by a few inches. After today's trip, no problem with the clamp on with just under 100 rounds down range, most suppressed.

**BoilerUp** · 20 February 2016, 16:51

For the record, the clamping screws on the Sentry 7 Clamp-On can easily make contact with the KMR with a little bit of pressure to deflect the 15" rail. This probably isn't an issue on the short KMRs as the dimensions of the gas block itself give it plenty of clearance and there is no contact with the rail if there is no pressure on the rail. The set screw version would be no problem (as others have already reported). Generally, I'd go with a set screw gas block anyway, but my WOA barrel has the notoriously over sized gas journal so a clamp on is the easiest fix.

Edit: note this is a 15" KMR over a rifle length gas system, so the block is pretty close to the end of the rail, which means enough pressure will deflect the end of the rail enough to make contact. I suspect on the shorter rails and gas systems wouldn't have this problem.

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