Selecting an AR barrel

[Irving]

I don't want to take the thread off topic, but I've also read that 9" is the most efficient length for 300BO barrels as far as getting a complete powder burn. Is this for all projectile weights and velocities, or only the heavy subsonics? I imagine there is a bit of difference depending on the burn rate of the powder used, and I assume that 9" is used as a general rule of thumb since differences in burn rate and velocity are negligible within an inch or two on either side of 9". Maybe we should start a new topic altogether for this question, but would you mind expanding a bit on that particular comment?

[SA Friday]

I don't want to take the thread off topic, but I've also read that 9" is the most efficient length for 300BO barrels as far as getting a complete powder burn. Is this for all projectile weights and velocities, or only the heavy subsonics? I imagine there is a bit of difference depending on the burn rate of the powder used, and I assume that 9" is used as a general rule of thumb since differences in burn rate and velocity are negligible within an inch or two on either side of 9". Maybe we should start a new topic altogether for this question, but would you mind expanding a bit on that particular comment?

I would start a new thread on this. It will be easier to find during a search that way.