Yeah, I'm not seeing the point. If bolt guns are common and powerful, they are not trivial weapons. I've seen folks run bolt guns in carbine matches and if they skilled, they are not that slow as to be taken lightly.
Also, I've read that Australian guns are making some nasty homemade SMGs. Finally, MSRs - give you my take. That term is idiotic and the Australian case is a prime one for that opinion. The 2nd Amendment doesn't protect sports. Calling the gun a sports toy makes it easy to justify a ban. In Australia from past discussions, the gun community tried to protect their guns as they for 'sport'. Australian males are supposed to have a 'sport'. Thus, don't take away our manly sport - not an SD or defense against tyranny rationale. It flopped. Guns were banned
Gun folks in the USA, like the major gun periodicals and NSSF, have tried the same excuse - it's a toy, it's for sport. Won't work.
Plenty of high end expensive, 'sniper' rifles in use today that are bolt guns. If they feel they need the plates, that's their call. The ban on semis isn't really that relevant.