Reply #48: A vacuum behind the bullet shouldn't be a problem.

[FeebMaster]

Although this is talking about rail guns and not coil guns like the Pskov 1100.

http://www.powerlabs.org/railgun.htm

If full power was to be applied to a static armature the rails and whatever was between them would instantaneously melt under the intense localized heat produced by Ohmic heating as 100thousand amperes tried to make it through the contact resistance. In order to prevent the Rail Gun from becoming a spot welder it is necessary that the armature be moving with some initial speed prior to electromagnetic acceleration. Most amateur designs fail because of lack of knowledge of this. In this design the armature is injected by a gas gun consisting of a 1000CC Schedule 80 PVC gas reservoir connected to a 30cm long barrel through a reducer that goes from 1/2"^2 to 1/4" x 0.6" through a 60 degree taper. A 1/2" diaphragm pilot operated solenoid valve controls the gas flow and essentially serves as the trigger for the gun. Approximately 5% of reservoir capacity is used in one shot. The system is designed for 500PSI (35ATM), enough to consistently fire a 6 gram aluminum slug out at 150m/s, or a Teflon slug at 195m/s (634.5fps, 696km/h, 432.6mph).


He's got some coil guns too:

http://www.powerlabs.org/gaussgun.htm
http://www.powerlabs.org/multistagecg.htm