I want to build a 12.5" 6.5 Grendel SBR  (already have 10.5", 14.5", and 19.5").  I want to do it in a super light weight with a Balios Lite receiver set, and need a light weight rail.

I'm wanting to use a lightweight thread-on suppressor (haven't picked it yet-  I have a 762-SD, but want much lighter), and would like the rail to end near the beginning of the can if possible.  I'm thinking a 12.5" barrel with about .6" inch muzzle threads would set the back of the suppressor back to about 11.9" or so.  With that in mind I'm thinking I want a rail that's about 11" to 11.5" long.  The closer to 11.5", the better.  I like the weight of the BCM KMR10, but just wish it was a tad longer.  I'm also looking at the Noveske NSR 11", but kind of prefer the mounting method of the BCM rail (anti-rotation tabs).

Thoughts, suggestion, pics of your lightweight 12.5" builds with long-ish rails?

P.S.--- I know some guys do builds with the can starting inside the rail "SD" style, but in the event that I need to take it somewhere that I can't use a can, I need to retain the ability to add a normal muzzle device that won't blow up the rail.  Also-- Most very light weight rails have inner diameters of 1.5" or less, so it'd likely be too small to fit a 1.5" diameter suppressor anyway.

Not sure if this helps or not, but figured I'd post it. I had a 16" Bison 6.8 upper with a YHM Lightweight rifle length rail. I wanted to have it cut down, but still able to shoot it unsuppressed. So, I had ADCO cut right about 4" off, so the ports on the QD FH mount were outside the rail. Even though you want direct thread, the idea would be the same for your standard FH. The YHM rails are 1.75" ID, so both my YHM LT and Saker 7.62 should fit inside the end of the rail. The LT was approved last week but stamp hasn't arrived at dealer...and the Saker just had the check cashed on 6/30, so I haven't actually test fit either.






And the scientific way I decided on 4" being the right amount:

I've seen a couple of light weight rails (sub 10oz.) that could be chopped, but usually by very little i.e. maybe .25" at most.  All of the cutouts in the lightest rails make it so they'd look screwy if chopped.

If only BCM made a KMR11.5

Your build looks pretty nice.  I like my other builds, but just have a wild hair to build something very light (Sub 5# I'm thinking).

I had an 11.5" barrel cut down to about 10.8" to get rid of the gap between the muzzle and rail.  I think you might be able to get away with a 12" handguard, but I would put it together with just the barrel and measure it to be sure.

Nice looking build.


Re: 12" rails--  The pisser is that most of the 12" rails I've been reading about are actually over 12.5" already (around 12.58").  That puts them past the 12.5" muzzle before even threading on the can back to roughly 11.9" in coverable barrel length.   I could grind/mill off a little bit, but no way could I take off almost 3/4" from the front of a lightweight rail.  You'd have broken slots looking ugly at the front.LOL

I could go shorter for the barrel length, but I already have a 10.5", and I really want the 12.5" barrel length.   Every half-inch counts heavily towards down range performance in barrels that short.

I am looking at a 12.5 barrel with a Samson 12.37 evo rail. Based on bow an 11.5 barrel and an 11 rail fit I expect the threads on the barrel to end very close to the end of the rail. With muzzel device it *should*  work. My intended supressor fits inside the rail, so that's a plus. An 11" rail would give plenty of clearance if the suppressor wont fit inside.

The evo rails are very light also. 11" rail is about 10 oz. 12" rail is 11 oz.

What length barrel and rail is that?  It doesn't look like a 10" rail (really 10" according to their website) on a 12.5" barrel.  It can't be the 12" rail on a 12.5" barrel either, because according to MI's website their 12" rail is actually 12.625" long....

If your barrel is really a 12.5", is that a 10" rail and your can sits back over your barrel more than the usual .6" thread length?

Okay, cool.  Thanks for the info.   A 12.5" barrel with 10" covered by the rail would leave 2.5" bare, then thread the muzzle device back over the barrel for a distance of .6" and that leaves a normal gap of 1.9".  Yours looks like it has a shorter gap than that.  What can are you using in that pic?  I like how it fills in the gap (aesthetically).  It looks "tidier" that way.  I know I shouldn't care, but the fashion queen in me is trying to figure out how to balance out the looks without adding undue weight.

That's the roughly 1.9" gap I'm expecting to see, and it doesn't look quite as bad as I thought it would.  Of course the rear of your AAC is sitting back a tiny bit further than the .6" threaded section of the muzzle too.  The 10" KMR is the obvious choice ounce-wise, and I may still default to it.  Thanks for the pic!

No problem for the pic. yeah the 11.5" looks good kmr 10" rail wise, but my 12.5" is just to good a shooter, and um that soft recoil .  But by the time I mount a light I really wont notice the gap.