What caliber?
Tons of sub 10.5” options for 5.56 out there, but that’s about as low as I’ll go personally, even on the guns I know I’ll always shoot suppressed. Fireballs aside, going that short’s pretty hard on components…fine if you’re religious about inspecting your bolts, etc, not so much if you just shoot and throw ‘em back in the safe. My daughter’s SBR has a 10.5” upper in 5.56, but she only shoots that with a can. Here’s my son shooting it a couple years back without the can attached:
Glamor shot:
So yeah, 10.5” is the shortest useable length for 5.56mm for me…. In my opinion, 12.5” with mid gas is a very nice sweet spot for short and maneuverable vs. accuracy and reliability In a 5.56 chambering. Here’s my workhorse 5.56 upper:
and my son’s SBR…also with a 10.5” upper in 5.56 and an 8” 300BLK with an SDN-6 can peeking out from under that hand guard.
Here’s his SBR next to mine in an older configuration from a few years ago:
Another 12.5” 5.56 tucked under a 14” handguard with a can here too:
I have an 8”, a 9” and a 10.5“ uppers in 300 BLK that work great…better than my 16” in 300BLK frankly. That’ll burn all the powder in ~ a 9” barrel depending on your load. I tend to only shoot that subsonic and suppressed these days now…tend to use all my sub-200 grain bullets in my .308 loads now…. LOL
For other calibers, there’s usually a recommended barrel length for the load you run…I have a 16” 6.8 upper and it works well for its purpose … used almost exclusively for pig hunts at night with thermal at 250-350 yards or so.
Also have both 450 Bushmaster and 350 Legend uppers… 16” for the 350 Legend (small deer rifle for the 120# or so runts we have running around here). This is the only pic I can find of that one right now (on the bottom)…and no, that light isn’t mounted in that position when in use…LOL. Had to stick it there to get it to fit in the safe between a couple other rifles:
That upper at the top in that pic is another 300BLK…. 9” barrel on that one. Here’s my other 300BLK upper on my PDW build:
…and the same lower, only with the stock opened, with yet another 10.5” upper in 5.56 (same TBAC-5C can though):
… and 12.5” for the 450BM thumper…also always paired with a can under a longer hand guard:
It’s a deep brush pig gun for me, always have that or my Ruger Scout rifle in the side by side out on the property for chasing game into brush.