You can use .OO buck, but you have to worry about ricochet. The plus side is depending on the quality of the door, you can penetrate with .OO....... there was a Marine I ran into at the hospital - they were clearing a hallway and the room doubled back. He reached for the knob to check it - the friendlies outside didn't realize he was on the other side - the way the room twisted, he didn't realize it come off the other hallway. He's missing the tips of some of his fingers from when the breacher fired the lock and his hand was on the other side.
So far as Russian reliability.....I don't know what it is about the Saiga, but they seem to have feeding issues unless you have had them worked on.
It must be an anomaly because I am a die hard AK fan. The little gas tube on my brand new M16A4 (I was the first one it was issued to) couldn't keep up with heavy intense fighting and clogged up and jammed - I had 2 malfunctions requiring remedial action within 5 minutes.......this while pinned down in the street and surrounded 360 degrees. I've put AKs through incredible abuse and they still fire. As an aside, we had guys slinging the M16s and picking up [dead] enemy AKs for the stopping power.
But, that's off topic. Truth be told, I intend to get a Saiga next as I already have a Mossberg. But if you are looking for a good versatile shotgun for breaching - I highly recommend the Mossberg, and also a breacher's kit - (hooligan tool and pry bar).
I have built my own gas-inpingment M4 clone (16" barrel including compensator, and wrong gas system, so not really an M4) and an M16A3 clone (no select fire). I haven't had any problems, but my shooting conditions are certainly not close to combat.
I reload my own M193 and M885 ammo in addition to some really low grain, fast sh!t for personnel armor penetration (those pesky varmints).
So I am curious, regardless if a weapon is an AK or an M10, is stopping power that different? Is it worthwhile to hump heavier ammo?