Would I regret a 12.5" 300 BLK barrel?

[oberstgreup]

With regard to barrel length, I was told for 300 to stay under 10 inches if shooting suppressed.

Why? The shorter barrel is a little handier, but I can't think of any other disadvantage to a longer one. A 12.5" does have one advantage: since it uses the same pistol-length gas system, it will have a longer dwell time which should give a little bit better functioning with subs. However, most people seem to have no trouble finding subsonic loads that will cycle the 9" reliably. But the longer barrel might give you a little more margin to play with different loads, especially subs with lighter bullets.

For the OP, I'd say get the barrel you want and then see about a rail. Losing a few bucks selling the rail and buying a different one is no reason to take something less than your first choice for the rifle.

[MegademiC]

I think a 12 might cause subs to go supersonic on occasion? I may be confusing it with 7.62x39 though.

I wouldn't worry about reliability, the system was designed around 8-10" bbl iirc. It's been a while since reading up on it, but I think rsilvers was heavily involved with the development of 300blk and suggested sticking to 8-10".

[BC98]

I think a 12 might cause subs to go supersonic on occasion? I may be confusing it with 7.62x39 though.

I wouldn't worry about reliability, the system was designed around 8-10" bbl iirc. It's been a while since reading up on it, but I think rsilvers was heavily involved with the development of 300blk and suggested sticking to 8-10".

All factory loaded subs are loaded to be subsonic in a 16" barrel. They will be slower in the shorter barrels.

[rsilvers]

I prefer 6-9 but 12.5 is more accurate on average and has longer range.