barrel break in --please show me some PROOF. -a copper jacket ,glides down a tube and does what?-it fouls.-you remove the copper fouling and she continues to do what it does. if you think that by shooting a hundred rounds,and cleaning every 5 shots or so is going to smooth out the bore and stop fouling,then you are sadly mistaken,unless your barrel is made from cs10/20.or st/10/12-cs 250.(22 rim fire).COPPER DOES NOT LAP EN4140--4153 OR 440 S/STEEL.-check the brinell or rockwell A scale.--after 40 years in the engineering game,i will stand corrected if some one can show me what im missing here.--heard this over the last couple of decades. if it works for you.well and good.-never had to to do all the cleaning break in stuff and think its BS.-P R O V E to me HOW it works.