i know for a fact that when shooting primer powered rubber bullets in my handguns, there's definitely a difference between std & mag!
38spl case w/std primer = 350fps from 2.5" security six; chrony 3ft from muzzle
38spl case w/mag primer=500fps from 2.5" barrel
44spl case w/std primer = 300fps from 3" bulldog at 3ft
44spl case w/mag primer= 400fps from 3" barrel
...also a very noticable flash from cylinder gaps with mag primers.
There's some really good advise on this website... I'd follow their lead when experimenting; the ones that are still alive anyway!
hunt when it's cold; fish when it's not.
South Louisiana IS the sportsman's paradise!