12.5" barrel characteristics ??
I have run 10.3-11.5" barrels suppressed and non-S for some time, but have fairly recently been trying 12.5. I have noticed what seems to me like a larger difference in operating group speed, and the associated functions, with 12.5 than with the shorter barrels.
For example, I have a Colt SOCOM I cut down to 12.5" with the factory .063" port. It is at the low end of the functionality range without the can, and at the high end with it. It's very over-gassed.
For comparison, I have an 11.5" that I have gassed to be reliable with and without a suppressor. With the suppressor, it runs well, but is not as over-gassed as the 12.5.
I would have thought that the 12.5 would be less sensitive to back pressure changes than the 11.5.
I'm interested in observations and experiences of others who run 12.5" barrels both suppressed and non-S.