308 sbr gas system length

[corey4]

i am starting to narrow down my build and getting hung on the barrel decision.

i originally wanted a 13.5 middy, but no one makes one. aero makes a 12.5 carbine. i know it's going to cost a bit more money (extra cost for the barrel and the cut/thread job), but i am considering getting a 16" middy and having it cut to 13.5 to get exactly what i want. any reason not go with a 13.5 middy? my reasons for the 13.5 middy is a bit more velocity and a smoother operating gas system. or am i being too picky?

build details:
aero m5e1 enhanced upper
aero lower
SLR agb
saker 762

[MistWolf]

In case you weren't aware, if you use an A5 RE with a 308 AR, it needs a carbine length buffer. This is due to the extra length of the 308 carrier.

[corey4]

Yes, and vltor also suggested a certain armalight spring as well.

[Failure2Stop]

Unsolicited advice, but I highly recommend against going under 14.5 with .308, and under 16" only if the user has a specific niche application and/or is shooting very light projectiles at at least moderate velocity.
Quite frankly (again, unsolicited, I know) if I had a need for a 13.5" .308, I'd buy a SCAR-H and the CQC barrel. I promise that it will save you a lot of headache.
Dropping under 16" of barrel makes a significant detrimental effect to ammunition performance, and while I like my 14.5" SR-25, I am demonstrably more efficient with my 16" guns.
Now, change that to a 13.5"-14.5" 6.5mm CM or .260 Rem and I will sing a different song, but that's better left to another thread.

[corey4]

i have a scar17 and i'm not really warmed up to it for some reason. i played with a buddies 12.5 308 SBR and liked it much better over the scar17. i have a seekins sp10 and like that much better as well over the scar17. i know, different animals and different uses, but im preferring the AR large frame animal.

[Failure2Stop]

i have a scar17 and i'm not really warmed up to it for some reason. i played with a buddies 12.5 308 SBR and liked it much better over the scar17. i have a seekins sp10 and like that much better as well over the scar17. i know, different animals and different uses, but im preferring the AR large frame animal.

I gotcha, just warning that 7.62 DI guns under 14.5" tend to be finicky.