i think the 223 will be the most plentiful the military uses it the most and alot of cizilians have rifles in it..everything from varmint rifles to assult rifles all in 223....the 7.62x.39 will never have it in America...about the only popular gun in it is a AK... but than again 7.62x39 is cheap as dirt and the people that do own them may have lots..we still have a few hunderd rounds laying around of it from when dad had an AK a while back...i dont htink its #1 though...maybe second but next to the 223 i think 308...alot of guns in all forms are chambered in 308...i have a FAL and 2 ar-15s in the house...i got 18 mags for my FAL alone..i duno what dad has for his 15' s..but he has more than enough ammo for the 15' s...308 ammo were down to about 500rds...if there was a war id be shooting 308 for my assult rifle and my 3006 for my sniper rifle...true classics never go out of style! man thats a scary thought..that really can happen..and thats when people try to rob eachother and when terrorists or other military groups try to take up over..in my neighborhood i dont know any gun owners except 4...and all i know they have is hunting rifles and shotguns...we are pretty prepared though...i know what to do because when im at school dads here and when im here dads working so i am the man of the house when im here..i have to know these things...i hope that doesnt happen though...