Can we get this to page 4 maybe on the "correct" term?
I would call it either, as Maxim named it... And they would be controlled or regulated whether it was called a silencer or a hoopa pah loopa.
A silencer can completely silence, as long as a person does not get too nit picky, on what silenced means. When the firing pin dropping is the loudest sound heard, I would consider that silenced.
Of course the bigger the volume of gas exiting the barrel, the bigger the can will have to be to contain it. Just like the huge mufflers on the new high horsepower cars and trucks. A bit of an aside, but a V8 can be very quiet when the exhaust is run through a 45 gallon drum. Don't even need baffles.
If you want to run a can on an M1 carbine, you will want an adjustable gas block, as the pressure being directed through will be a fair bit more due to the back pressure/volume from the suppressor (You win that one, terminology Nazis!
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You'll note that I referred to it as a suppressor there, as the bullet travels quite a bit faster than the speed of sound with a convential load. Possibly could run a heavier bullet like a 200 gr. roundnose to get subsonic, to quiet it down. Of course it will probably not open up very much at those speeds.
I was always intrigued with doing a big bore, as it would not seem like you are giving anything up. A .450 Bushmaster would be pretty neat with heavy bullets. Of course so would a 50 Beowulf, but unless you are casting, I don't believe there is many good sporting bullets for it.
Of course being a lever guy, a suppressed 45-70 is a natural fit. A 500 gr. (or so) flat nose at a little over 1000 fps still has a heck of a thump on the receiving end, no gas block to mess around with, and an exposed hammer eased back, is about as silent as you can get... Oh yeah!
Low speed, high drag! No, wait....