Heat

My dick has a gentle curve up, so 5.45x39 would fit me like a glove. Also, this is now my headcanon for the vaginal shapes of gungirls.
The ones with multiple branches like 5.56 would need to be reduced to a single path though, that shit would just lead to weird health problems in a vag.

It has that squeeze part in the middle, that's gotta feel good.