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1/22/2020 12:12:56 PM
Posted: 1/18/2015 11:05:48 AM EST
I am building a rifle with a sixteen inch barrel and it had a mid length gas system. If I use a high profile gas block what is the longest rail i can use? And if i go with a low profile gas block how long of a rail could I use? I'm going to use a free float system. Any help here would be great thank you.
Link Posted: 1/18/2015 11:20:18 AM EST
A 9" rail will end just before the front sight base of a middy.
A 10" rail is about the minimum to cover a low profile gas block on a middy.
Link Posted: 1/18/2015 12:29:59 PM EST
Thank you.
Link Posted: 1/18/2015 6:37:25 PM EST
Anytime. Good luck with the build!
Link Posted: 1/19/2015 2:14:10 AM EST
[Last Edit: 1/19/2015 2:16:17 AM EST by sauceboss]
look up samson they make great quad rails. standard or railed gas block you can use their EX line to get some extra space.

if you go low profile i'd look at a free float tube over a quad rail ( i like both), they're lighter and if you're going for the longest length possible (15 inches i believe) weight does matter.

samson makes regular rails as well without cut outs if you want a long quad rail.
Link Posted: 1/19/2015 8:48:02 AM EST
Seekins makes awesome free float rails. BAR (quad) and MSCR (Smooth Modular Keymod) rails in 7, 9, 10, 12, 15.... if i recall correctly.

All attach to the same nut with 8 bolts. So you can swap sizes and styles if your first choice is too short or too long.

And they resell pretty well on the EE.

And they have a large interior diameter for covering gas blocks and suppressors.

I love all of mine.

And Seekins makes some rails for other companies that are compatible with the attachment nut. Like these Radical modular quad. Which is currently on my high end AR.

https://www.primaryarms.com/Radical_Firearms_Seekins_15_Radical_Rail_p/rf15rail.htm
Link Posted: 1/19/2015 10:03:38 AM EST
If you use a low profile gas block on a 16" mid-length barrel, you can use anything from 10"-15". Most all free-float handguards will clear any low profile gas block. I used a 15" hanguard (Midwest Industries SSM M-LOK series) on a recent build where I used a 16" mid-length barrel and low profile gas block.




This is a 12" handguard with a 14.5" mid-length.




Here is a 10" Geissele handguard on a BCM Jack Carbine with a 14.5" mid-length.




These should give you some idea as to what it may look like.
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