View Full Version : Rail that will fit over 1.5" inside diameter .936 Gas Block?
Swapping out my one pound tube on my 20" White Oak upper and would like to go with a lighter 15" rail that would cover the .936 GB with an outside diameter of 1.5"......any suggestions? Most everything is 1.5 with the exception of Seekins line of MCSR/SP rails. Any idea what the ID of the Geissele MK4 MLOK rail is? I'm guessing it's 1.5 as well.
The Geissele I have here is around 1 3/8" ID for the round part. Don't know what size you need.
Yeah, that Geissele won't work....I stumbled onto the Odin Works KMOD rail which is 1.6 ID which would barely work but it's doable. I also like that they offer a 15.5" rail in FDE. Looks like those are my choices. This search brings me to a talking point with rails that are all under 1.5" ID and the popularity of suppressors......companies need to step up and start producing rails that are more accommodating.
The one I measured is a Mk2 but I believe the Mk5 I have is the same ID.
The GB isn't 1 1/2" OD. It's probably 3/4" radius from the center to the top of the tower where the tube inserts. The way most hand guards are extruded there is a pocket beneath the top rail that is out of the ID. The tower on your gas block will occupy this space if it is large enough. I hate to recommend a site I don't particularly like but there are a lot more guys over at the Hide that sport big barrel AR target rifles. You might get an answer faster over there.
I'm just using WOA specs on their site:
https://www.whiteoakarmament.com/xcart/product.php?productid=17656&cat=287&page=1
Match rifle gas block fits .936" diameter barrels.
Gas block outer diameter at the widest point is 1.5 inches.
I already tried to install my MI SSK rail on my WOA barrel with .936 GB installed and it wouldn't clear.......and the ID listed on that rail is 1.3". Perhaps I'm approaching this wrong?
Haven't seen that one before. I stand corrected. Take a look at this one. http://www.brownells.com/rifle-parts/gas-system-parts/gas-blocks/micro-936-gas-block-prod54725.aspx
I would just swap gas blocks and then use whatever hand guard I wanted.
Okay, so my barrel is only dimpled on one location underneath the gas port so I was trying to avoid dimpling myself if I can avoid it.....the GB from WOA is a clamp on style that doesn't utilize a set screw on the bottom. I guess using a clamp style Low Pro is an option, but then I'm out another $40-$50 in addition to the rail. I think the Odin Works 15.5 KMOD with 1.6" ID will work.....as will the 1.8" ID Seekins, which are both solid and viable options.
Haven't seen that one before. I stand corrected. Take a look at this one. http://www.brownells.com/rifle-parts/gas-system-parts/gas-blocks/micro-936-gas-block-prod54725.aspx
I looked at that DPMS GB but after looking at the specs, it is described as this:
SPECS: 4140 steel, matte black phosphate finish. Fits barrels with .936” O.D. at gas block. This will fit in any free float tube with internal diameter of 1.75 (which should be most free float tubes) and this will work with the 308 SASS barrel also.
1.75 ID puts me back to square one.
Rayrevolver
07-30-15, 18:34
I think 1 out of 2 dimpled set screws is still better than a clamp on.
How about this:
https://www.primaryarms.com/Midwest_Industries_low_profile_gas_block_Bu_p/mctar-lpg.936.htm
I think 1 out of 2 dimpled set screws is still better than a clamp on.
How about this:
https://www.primaryarms.com/Midwest_Industries_low_profile_gas_block_Bu_p/mctar-lpg.936.htm
Interesting....any particular reason why? I am in agreement with you on pinning, dimpling etc. over clamp on style, but I haven't had any issues utilizing clamp on GB in the past (My current WOA upper included).
Okay, so my barrel is only dimpled on one location underneath the gas port so I was trying to avoid dimpling myself if I can avoid it.....the GB from WOA is a clamp on style that doesn't utilize a set screw on the bottom.
You don't really need two dimples in order for the GB to be secure. 1 dimple should be fine if the gas block uses the correct knurled cup set screws. Then secure 2nd screw w/ red loctite. IG also instructed me a while back that If desired you could also apply green loctite to the gas block journal for more security.
Aero Precision handguards are fairly large ID at 1.8". I don't tend to like that but it might be helpful for you.
Rayrevolver
07-31-15, 13:18
Interesting....any particular reason why? I am in agreement with you on pinning, dimpling etc. over clamp on style, but I haven't had any issues utilizing clamp on GB in the past (My current WOA upper included).
I have read that people on M4C have had good luck even without the dimple (see thread below, recommend dimple at least the AFT set screw). The general consensus was NOT to use clamp on blocks.
I had a set screw+dimple GB shoot loose (installed by a well known builder) and based on recommendations from M4C, I bought some McMaster Carr set screws:
McMaster-Carr Pointed Set Screw, 10-32x 3/16 Part. No. 90289A337
EDIT:
https://www.m4carbine.net/showthread.php?169034-Non-dimpled-Barrel-and-Set-Screw-Adj-Gas-Block-Install-Advise
EDITED again:
Crap... I bought the wrong type of set screws. Going to Adco for pinning anyhow.
Set screws with a pointed end would benefit from a dimple.
Set screws with a cookie cutter end will bite into the metal when installed.
With that said I just purchased an MI .936" low profile GB for my Lija barrel. The MI GB uses three set screws and will bite into the machined flat on the barrel.
Test fitted a PWS 15" rail that is 1.35" I.D. and have room to spare.
Now to get started with my build :)
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