They are a sheet metal cup that is pressed on to the back of a lead bullet to hold the pressure better, sort of a gasket on the back.
The velocity limit of cast bullets is dependant more on the hardness of the alloy than anything else. The use of gas checks should increase the limit by 300 to 400 fps. I use an alloy of 95% wheel...
Methane: CH4 Ethane: C2H6 Propane: C3H8 Butane: C4H10 Usually a mixture of these.
natural
awesome things like, propane or natural gas :) ;) :D LOL! hi you people are weird!!!!!!! :p
I'm not sure about the tear gas but laughin gas is nitrous oxide or N2O.