What Rastus said. I have 2 cans. I love them both, though I don't use them as often as I thought I would. Mostly because they are a pain to clean. Definitely a fun toy. Both of mine are Gemtech. I have never had a problem with either of them.
I've not shot my Yankee Hill Machine Phantom 7.62 can (it's the quick disconnect model) yet on my .308 Savage as I need to get a scope mount and rings for the rifle. I have tried a few shots with it on my .223. It's certainly not silent but I can definitely shoot without earmuffs.I use my .22LR suppressor almost every time I go shooting. I put on my Buckmark and AR conversion upper. Supposedly one can get a desktop sandblasting setup from Harbor Freight that makes cleaning the lead off a breeze. I've not done that yet but cleaning them can be a bit of a pain but I probably had 1000 rds. through mine before it was cleaned. Sure there was some lead build up but nothing horrendous.
Nope, as mentioned, I've not tried it. Apparently there are different media that you can use that have abrasion characteristics so you can find one that doesn't damage the baffles. I forget where I heard this at, maybe silencertalk.com.