barrel length vs bullet type
I don't know for sure, but would guess you'd need faster loads from shorter barrels; and faster opening bullets, since reduced barrel length usually results in reduced velocity.
Is there a general "rule of thumb" about type of SD projectile preferred for 3.5" vs 4.5" barrels? (That is G26 vs G17; G39 vs G38; etc.)
There's a fundamental flaw in a system that passes laws that put an onerous burden on law-abiding citizens, but fails to prosecute the criminals who break those laws.