I load two 20G shells. 7/8 oz in Remington hulls, use in 20G Barrels on a 12 G Beretta o/u and Beretta 391 Autoloader either one usually carry LM chokes. And 3/4 oz in AA hulls oz for my Two Parker Trojan 20’s. The Parkers are tight choked, result on target patterns 3/4 7/8 are about the same. Parkers lighter with slimmer stocks pleasant to shoot with 3/4, felt recoil about the same as the 8 lb Berettas (391 weight added) (different hulls easy to identify.)
Loading 3/4 best information is a sticky on Shotgun World reloading page
https://www.shotgunworld.com/threads...ustice.421067/
In practice only difference wad, bit less 20/28 powder & little adjustment to the press. Factory 3/4 20s great SxS shells problem is reliable supply.
William