13.7 vs 14.5 vs....


Verified Military
Sep 5, 2019
Looking to purchase a rifle (crossing fingers Sons Of Liberty Gun Works has a Black Friday sale like last year...) and considering their options on doing a 13.7 build with the permanent muzzle device to bring it to non-SBR land... There's obvious physics and ballistics to consider, and already have been, but anyone want to jump into the can of worms of discussing/providing personal anecdotes regarding their thoughts on the matter? Intended as a do-most-things-good-enough rifle.
The difference in ballistics as determined by barrel length of a 13.7" and 14.5" is negligible (as is 16" and 18"). The difference will be somewhat more pronounced with ammo choice. To me, a 13.7 isn't even an option unless I want a SBR (and I would not in that length). Get a pinned 14.5" or a 16" and call it a day. Today's barrel material choice, ammo choice, and optic choice, a 16" can be deadly at 600 yards. If you want a jack-of-all-trades rifle, either of those barrel lengths with a (true) LPVO and good ammo would be solid.
A few things to think about if you are about to build an AR-15:
Are you building a rifle because you want to shoot in 3-Gun matches with it?
Are you building a "BBQ Gun" that you will ONLY bring out to show your buddies when you are waiting for the ribs to finish smoking?
Are you building a rifle for the SHTF moment when the zombies start swarming your yard?
Are you building something that might be used to shoot hogs ?

Just my two cents but I don't see the utility of pinning a barrel on a "work" gun. It doesnt matter if it is for hogs or zombies, pinning an oversized muzzle device on a barrel just to "make it legal" is something that you should only do to a BBQ-Gun.

-If you plan on taking it out and using it for 3-Gun - stick with a 16 or 18 inch barrel (my opinion of course)
-If you are building a BBQ gun - why stop at 13.7 - just build a "pistol" with an "arm brace" then you could put a 7.5 or a 10.5 or any other "pistol" barrel and still not have to worry about SBR problems.
-If it is a SHTF gun, a 16 is short enough to maneuver easily but long enough to accurately engage bad guys several football fields away.
-If you are building a hog gun a 16-18 would be just fine

An AR-15 is one of the most versatile platforms on the planet. If you want to shoot targets at long range, toss on a 6.5 Grendel upper and away you go. You need something to shoot BIG hogs - find an upper in 300 Blackout or 458 SOCOM and have at it. If you just want a tactical rifle with anodized M-LOK hand guards and wicked cool flash suppressors - there are more vendors than you can shake a stick at that will give you the coolest looking gun since Han Solo popped Greedo with his custom DL-44

...and because of the AR's inherent versatility, with one well built lower receiver, you can have a BBQ gun, a target rifle, a SHTF rifle, AND a Hog Killer for just a fraction of the cost that you would spend on four or five special purpose rifles.
Last edited:
Barrel length in this range is a choise secondary to muzzle devise. Pick the devise you want or need for a suppressor host then get a barrel length that bring it just to 16. Say you want a warcomp well a 13.7 can get you to 16. But you’ll be at 17 with a 14.5.