Hey Norm,
I shoot suppressed quite a bit, the .300 Blackout is the only one of the calibers you mention that I can shoot with the can because it's a .30 caliber (Banish 30) with subsonic ammo it's very quiet and very accurate. I shoot a good amount of supersonic ammo through my can also and it's not obnoxiously loud either, the sound of the bullet hitting a deer in the ribs seems louder than the report from my .277 Wolverine. As far as loading, the .300 BLK brass can be made easily from .223/5.56 brass and there are lots of .30 caliber bullet options, subsonic loading is a little different in that you typically work down from the starting load. If you go with the .300 I have a superb load I'll share with you using the 200 grain Nosler Accubond. As far as suppressors go I really like my Banish 30 and Banish 22 from Silencer Central, they are 100% titanium construction and user serviceable.