karnaaj
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Will a 12" rail completely cover a low profile gas block on an 18" barrel with a rifle length gas system?
Question about rail length
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Arizona_Mike
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I believe about 1/4-3/8" will stick out if it is exactly 12", the reason many vendors offer a 12.37"
Mike
Mike
karnaaj
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That sucks. I was going with a Rainier Arms Force Free Float System in 12". I really don't like the looks of a 15" rail on an 18" barrel but I don't want the gas block showing either. Guess it's the 15".
Arizona_Mike
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I would need to check my guns because I like adjustable gas blocks and I usually pick components to get the gas block as close to flush as possible. It's been too long since I measured.
The gasport locations as measured from the barrel shoulder (which the barrel nut pushes on) are:
Carbine: 6.75" (nominally 7")
Mid: 8.75" (nominally 9")
Rifle: 12.125" (nominally 12")
For rifle length the gasport location is 1/8 greater than the nominal length while it is 1/4" less for Carbine and Mid. That is 3/8" further for rifle. Most of my builds have been Mid so if your take my experience about part of the gas block sticking out on Carbine or Mod and add 3/8" it looks like the gas block will be completely exposed as strambo suggested. I've only built one rifle length and for that I used a 15" handguard.
Mike
The gasport locations as measured from the barrel shoulder (which the barrel nut pushes on) are:
Carbine: 6.75" (nominally 7")
Mid: 8.75" (nominally 9")
Rifle: 12.125" (nominally 12")
For rifle length the gasport location is 1/8 greater than the nominal length while it is 1/4" less for Carbine and Mid. That is 3/8" further for rifle. Most of my builds have been Mid so if your take my experience about part of the gas block sticking out on Carbine or Mod and add 3/8" it looks like the gas block will be completely exposed as strambo suggested. I've only built one rifle length and for that I used a 15" handguard.
Mike
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bangswitch
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Geissele makes a 13" rail; I've got their Super Modular Mk2 on my 16" carbine gassed gun, and the block is well hidden. A rifle gassed barrel should have the block just inside the 13" rail.
I have a build going on where I have the Rainier 15" Evolution rail over a Rainier 18" SPR barrel with a low-pro gas block and rifle-length system. I'll post some photos if I get a chance. It actually looks quite good.
I spent a long time looking at 12.5-14" rails and couldn't find one to match my needs. I have no qualms about going with the 15" rail.
Arizona_Mike
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A lot of vendors have their own versions of the Samson Evolution rail (usually different vent designs and different tabs to fit their receivers) but I generally only buy the KeyMod version from Samson themselves and then a few licks of a hand file to modify the tabs to fit any billet or 7.62 receiver.
My last build used a magnesium alloy BCM KMR handguard and I loved it (almost as light as carbon fiber and very rigid). They make 10.5", 13.4", and 15". They are a little more expensive than the Evolution but not too much.
Mike
My last build used a magnesium alloy BCM KMR handguard and I loved it (almost as light as carbon fiber and very rigid). They make 10.5", 13.4", and 15". They are a little more expensive than the Evolution but not too much.
Mike
Zerodefect
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I have a 14" DD lite rail on my 18" rifle. Get the 15" BCM KMR.
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