11.5 inch is what I would do for SBR, I am building a 223/556 with 11.5 barrel, ofcorse with a can .

Military likes 6.5" barrels in the 300 Blackout as they want compact guns for CQB type work. Most experts/industry people says 8.5-10.5" barrel is the best range. I have a 10.3" and 10.5", with a can they don't feel long, though don't feel short either. I see everything from 5.5" to 16" barrels but feel like you get the most out of a 9-10", that is high velocity and sub sonic shooting. If you are only shooting sub sonic loads and want compact OAL do a 6"-8" barrel. Those big 220gr slugs shoot fine out of the short barrels. Remember shorter barrel equal less velocity means quieter gun.

Chornograph data shows 220gr sub loads run around 950 fps from a 10.5" while the 150gr run 1750 fps.

Gunner

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N/T

Going off of memory, but the .300 blk aka .300 whisper was developed with around an 8” barrel in mind, shooting subsonic, suppressed. I’d have to check mine but I believe my sbr is either 8” or 8.5” and si mainly shot suppressed (99% of the time) sit subsonic ammo (80% of the time) and performs as expected.

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Even using 220 gr at purported subsonic velocity, and using the Surefire RC2 suppressor which you are familiar with, both Tom & I were surprised at how loud it is.

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https://palmettostatearmory.com/psa-8-5-pistol-length-300aac-blackout-1-8-phosphate-7-l...

PSA is calling

Gunner

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41 Mags rule, Baers rock!