13.7" AR: Pros and Cons

[Stickman]

I threw my BE Meyers on my 14.5", it is a little bit longer than 16", but keeps everything pretty close and doesn't ride under a rail. With the Centurion Arms CMR, it is perfect for barrel coverage (if that is a concern).

[nate89]

It's been awhile since I started this thread, and I figured I would write a quite update for anyone who cares. I did end up building a 13.7 gun, with the following parts

MUR Upper
BCM BCG
Geissele CH and MK14 13" forend
13.7" Ballistic Advantage Barrel, pinned gas block, and gas tube with a double shimmed Dead Air flash hider pinned and welded to ~16.1"
Dead Air Sandman-K lives on this gun
Rainier Ultramatch (ambi) lower
BCM LPK
LAW folder
Vltor A5
Magpul SL-S stock

I added a two-point sling, Trijicon 1-4 in a Larue 1.93 mount, and called it good. Since building it I have shot it in a couple two-gun competitions, took a Sage Dynamics two day carbine class, and basically used it as my go-to rifle since I finished it. The TL;DR: if I had to go back I would pretty much have built it exactly the same. In my experience BA has very reasonable gas port sizes, and this 13.7 is no exception. I originally has a bootleg adjustable bolt in the gun, but found it unnecessary with the Sandman-K, and replaced it with a standard BCM BCG. The gun shoots very well with and without the can.

Although I haven't done any serious accuracy testing, in preparation for the Sage class I had a range session that was primarily getting a solid 200 yard zero, as well as testing for holds at different distances. Out to 300 from prone shooting monopod on the magazine I had no problem keeping a good group on cardboard USPSA targets that I had on hand, and steel out to the same distance was not a problem. I'm sort of interested in exactly what the accuracy is, so hopefully soon I can go out and really get some decent data.

Opportunity cost: myself and pretty much everyone else has a finite budget, so would I give up other barrel lengths to have this gun? I would pick this gun for a 'general purpose' gun over any barrel length that I either currently have or have owned. I have an 11.5" SBR, and like shooting this much better. I know many people regard the 12.5" gun as the optimum 'general purpose' barrel length, but getting a bit longer handguard, and only adding about 1" to the gun that also eliminates any NFA considerations is a good trade for me.

The only real downside I hear from people is "well now you can't change muzzle devices as easy." My response now is "who cares?" I have a 16" BCM upper I bought over 6 years ago with an A2 flash hider on it. I have never had some burning desire to play barbie with the gun and be constantly swapping muzzle devices to the new hotness. Owning Dead Air cans made the decision of muzzle device very easy, and I have never wished I had anything else on it. Maybe after 10K plus rounds through the gun I'll need to replace the barrel or something, and I can do that when the time comes.

The 13.7 gun is shorter and handier, especially with a can, than my 16" guns, while still remaining a title 1 firearm. It also is almost as handy as my 11.5 BCM while having more real estate on the handguard, higher velocity, and smoother shooting. I have been slowly eliminating accessories and guns that I don't use, and getting duplicates of the ones I shoot a lot. My plans in the near future are to build a replica of this upper. Most likely I'll just keep the muzzle device unpinned and use my SBR lower unless I find the need to use this on a standard lower.

If you care about a 13.7 project, hopefully that gives you one person's opinion about the idea.

[jdgiii]

It's been awhile since I started this thread, and I figured I would write a quite update for anyone who cares. I did end up building a 13.7 gun, with the following parts

MUR Upper
BCM BCG
Geissele CH and MK14 13" forend
13.7" Ballistic Advantage Barrel, pinned gas block, and gas tube with a double shimmed Dead Air flash hider pinned and welded to ~16.1"
Dead Air Sandman-K lives on this gun
Rainier Ultramatch (ambi) lower
BCM LPK
LAW folder
Vltor A5
Magpul SL-S stock

I added a two-point sling, Trijicon 1-4 in a Larue 1.93 mount, and called it good. Since building it I have shot it in a couple two-gun competitions, took a Sage Dynamics two day carbine class, and basically used it as my go-to rifle since I finished it. The TL;DR: if I had to go back I would pretty much have built it exactly the same. In my experience BA has very reasonable gas port sizes, and this 13.7 is no exception. I originally has a bootleg adjustable bolt in the gun, but found it unnecessary with the Sandman-K, and replaced it with a standard BCM BCG. The gun shoots very well with and without the can.

Although I haven't done any serious accuracy testing, in preparation for the Sage class I had a range session that was primarily getting a solid 200 yard zero, as well as testing for holds at different distances. Out to 300 from prone shooting monopod on the magazine I had no problem keeping a good group on cardboard USPSA targets that I had on hand, and steel out to the same distance was not a problem. I'm sort of interested in exactly what the accuracy is, so hopefully soon I can go out and really get some decent data.

Opportunity cost: myself and pretty much everyone else has a finite budget, so would I give up other barrel lengths to have this gun? I would pick this gun for a 'general purpose' gun over any barrel length that I either currently have or have owned. I have an 11.5" SBR, and like shooting this much better. I know many people regard the 12.5" gun as the optimum 'general purpose' barrel length, but getting a bit longer handguard, and only adding about 1" to the gun that also eliminates any NFA considerations is a good trade for me.

The only real downside I hear from people is "well now you can't change muzzle devices as easy." My response now is "who cares?" I have a 16" BCM upper I bought over 6 years ago with an A2 flash hider on it. I have never had some burning desire to play barbie with the gun and be constantly swapping muzzle devices to the new hotness. Owning Dead Air cans made the decision of muzzle device very easy, and I have never wished I had anything else on it. Maybe after 10K plus rounds through the gun I'll need to replace the barrel or something, and I can do that when the time comes.

The 13.7 gun is shorter and handier, especially with a can, than my 16" guns, while still remaining a title 1 firearm. It also is almost as handy as my 11.5 BCM while having more real estate on the handguard, higher velocity, and smoother shooting. I have been slowly eliminating accessories and guns that I don't use, and getting duplicates of the ones I shoot a lot. My plans in the near future are to build a replica of this upper. Most likely I'll just keep the muzzle device unpinned and use my SBR lower unless I find the need to use this on a standard lower.

If you care about a 13.7 project, hopefully that gives you one person's opinion about the idea.

Another muzzle device option if you’re running Deadair or any key-mo comparable can is the SOLGW NOX. It is slightly longer than a Deadair flash hider or brake and will bring a 13.7” barrel to 16” without extra shims.

[nate89]

Yes, I have looked into that for the muzzle device on my next 13.7. I know it is quality, but I have also heard of it being more concussive to the sides than the warcomp. Honestly I will probably buy one at least to try out, and if it's not for me I'm not out a ton of money, and I'll hopefully will have learned something. I do like it for the little bit of added length to eliminate the need for a second or thicker shim. I have not had a single issue with alignment with my set-up as is, but a single shim for timing has to be better than the two thick and one thin set-up I have currently.

[kirkland]

Just get a 16" rifle if you want to take it out of state without filling out a 5320.20. Just search the forum and look how any people regret pinning.

But I already have a bunch of 16" inch rifles and I don't want to deal with the paperwork and fees hassle of aquiring an SBR, taking it out of state, transfering it. So it's Pinned and welded or pistol shorties for me!