If your barrel isn't from a reputable manufacturer, you might want to have a smith check the concentricity of the threads to the bore, if you're concerned about it. What twist is your barrel? As others have said, if you're worried about stability, put some through paper without the can on, and if they're tumbling, you'll see them going through the paper off-center (the holes won't be round). If you have pistol length gas, AA1680 and IMR 4227 do just fine at cycling the bolt with the can on while shooting subs. Loading subs is a little different than you're used to - you start with a known safe load and work your way down until you get reliably subsonic and reliable cycling. Carbine length gas makes things a little more iffy, but I don't seem to have problems with either powder with the can on either. Supers will always cycle the bolt.
ETA:208 Amax generally works just fine. As you go below 200 grain bullet weight, it becomes more difficult to get cycling at subsonic velocities/pressures without a lot of adjusting. I use Palmetto Projectiles' 203 grain powder coated lead rounds (which requires flaring the case mouth like a pistol round to prevent shaving lead) for practice on steel. They work very well, and are very low cost.