16" Barrel: How long should the rail be?


April 25, 2013, 08:56 PM
I've purchased the following barrel for my first ever AR build:



It is 16" in length, as the range I'm going to use it on is fairly short, I prefer sacrificing the extra length for reduced weight.

From what I've heard, there's tons of good rails out there, but have heard especially good things about the Troy Alpha rails.

See here:



Is a 15" rail an appropriate size to use on a 16" barrel? As I've never build an AR-15 before, I'd appreciate any vet's chipping in their thoughts as to what is the plus/minus equation of using say a 15" rail versus something smaller. Besides the slightly reduced weight of the shorter rail, and the cosmetic difference, do you guys generally recommend having a rail about the same size as the barrel, or quite a bit shorter? Also, beyond the Troy rails, what are your personal favorites that are high-quality and lightweight? I'm open to new ideas.

I'd love to hear your thoughts. Thanks!

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April 26, 2013, 09:00 AM
Many 16 inch barrels come with a 7 in or 9-10 in rail, depending on the gas system. I personally have a Midwest Industries 12 in on mine. I wanted a longer handguard because I am 6' 6'' and I needed more real estate for my long arms to run it the way I wanted to. I needed to free float as well so it seemed a good choice. Any longer rail does add weight, and it is adding that weight to the front end of the gun which is already heavier on most ARs. I think 15 in may be overkill, but I know some run them that way and love it.

April 26, 2013, 09:29 AM
It is a matter of preference. If you like the 15" handguard then go for it. The benefit is large real estate for different grip positions and flexibility with accessories. It also allows you to mount the front sight closer to the muzzle. The main downside is the extra weight. the longer the rail the more weight you add. My buddy swears by the Troy free floats - namely the Alpha. They are very nice but it depends on how you want to use it.

April 26, 2013, 10:16 AM
I got a Midewest Industries 9" for mine. Just long enough to cover the Gas block on a carbine length system and allowed me to use the end plate.


April 26, 2013, 10:44 AM
A 9" railed forearm is plenty long enough for my 16" carbine. As mentioned previously, the longer that rail becomes, the more nose-heavy and unbalanced the rifle becomes.

FYI - I now have Magpul angled foregrip mounted to this rifle, and there is still plenty of room to mount it pretty far forward, with a little room to spare.


April 26, 2013, 11:14 AM
it's mostly personal preference, depending on how you intend to use the rifle.

obviously, the main purpose of the rail is to give you something to put your hand on without touching the barrel (which is HOT and will shift your POI). so, where do you plan to put your hand? or are you mostly going to shoot off bench rests and bags in which case you need a rail that is flat on bottom and slides on bags easy

secondary purpose is protecting the gas block and tube. not so much for the double-pinned FSPs but is a little more important for the smaller ones that are only held in place by a set screw. you go slamming it into a rock and it shifts 1/8th inch left or right and you now have a straight pull bolt action.

April 26, 2013, 02:02 PM
If you have a fixed front sight (http://www.midwayusa.com/find?sortby=1&itemsperpage=24&newcategorydimensionid=9704), match the rail to the gas system (Carbine, Mid-length etc). If not, you can use a low profile gas block (http://www.midwayusa.com/product/335471/yankee-hill-machine-gas-block-low-profile-set-screw-ar-15-lr-308-standard-barrel-0750-inside-diameter-steel-matte) and whatever length rail you want.

April 26, 2013, 02:31 PM
Walkalong I used a cutout rail on mine. This one in fact from Midwest, it's just another option for if you want the solid mount of a FSP and don't want to fool with the gas system.


April 26, 2013, 05:46 PM
I have a 16 inch midlength with an A2 front sight. I used a 9 inch alpha rail on mine and its worked perfectly

April 26, 2013, 06:30 PM
Walkalong I used a cutout rail on mine. This one in fact from Midwest, it's just another option for if you want the solid mount of a FSP and don't want to fool with the gas system.Forgot about those. :)

April 26, 2013, 06:38 PM
This would be MY ideal setup... YMMV.


April 26, 2013, 07:27 PM
I have a 12" Midwest Industries SS12 gen 1 on my S&W 16". Anything less than 10" is uncomfortable for me. A 15" is ok, but i never do need that extra rail. 12" is perfect for me. I am 6" average build. The ergonomics of a long rail fit me better.

Edit: My 15-22 has a 10" rail. It feels good.

In the set up below, i grab the end of the rail with my thumb over the tube. I really don't use the vert grip any more. I only use it as a hand stop now.

http://i33.photobucket.com/albums/d68/50_BMG/Guns/SW032012a.jpg (http://s33.photobucket.com/user/50_BMG/media/Guns/SW032012a.jpg.html)

April 26, 2013, 08:44 PM
Here's the upper receiver and barrel I've purchased to go along with this project:





The barrel looks low enough profile that I think it should slip easily enough inside of the Troy rails or something similar. I'm curious though, do I need any other hardware to connect it to the upper?

I purchased this PSA parts kit to go along with it, but these are all lower parts:


April 26, 2013, 10:27 PM
You need a low profile gas block and that rail will fit fine.

good choice on parts. PSA makes good stuff. I've used their parts several times.

April 27, 2013, 03:11 AM
Thanks for the heads up.

Was looking to get this one, your thoughts?



April 27, 2013, 10:14 AM
That should work just fine. Looks huge though. :D

I turned a .223 carbine upper into a .300 BLK and used a mid-length tube and a low profile gas block. I believe I used a different brand, but they are all similar.


April 27, 2013, 11:48 AM
YHM is good stuff, but i like Daniel Defense for gas blocks.

You have M4 feed ramps on the barrel and not on the upper. That will function but i like them to match. Your combo is the bottom right.


April 27, 2013, 06:31 PM
Good catch gotigers. I did not follow the links and see that.

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