'Compression projectile' definitions:

Definition of 'Compression projectile'

From: GCIDE

Compression projectile \Com*pres"sion pro*jec"tile\ A projectile constructed so as to take the grooves of a rifle by means of a soft copper band firmly attached near its base or, formerly, by means of an envelope of soft metal. In small arms the modern projectile, having a soft core and harder jacket, is subjected to compression throughout the entire cylindrical part. [Webster 1913 Suppl.]