Hello Gentlemen. Im trying to figure out this twist rate thing for my Russian SKS and Norinco 7.62x39 rifles. i am shooting the lee 155 and 160 gn cast boolits made for this rifle. I am having good results in the bolt action norinco using the 155 grainers at about 2-2 1/2" at 100 y and if i clip the tip off giving me a flat nose and about 146 grain even better at 1 3/4" at 100 y. by the way, gas checked and sized to .312 wheel weights bn of 15. 14 1/2 gn of alliant 2400.
when i try this load in the sks and anywhere up to 16 1/2 gn of the 2400 i get 4" AT ONLY 50 Y. Im not quite ready to give up yet. so I did a little looking on the net and trying to figure the twist rate to bullet stability. according to the formula i should have a twist rate of 1:16 not 1:9.5 like the sks is. according to the trist rate formula i should be shooting a bullet that is roughly 1.45" long to match the barrel twist rate. well for this sks, that would be like lobbing a cannon ball from a sling shot. Im not sure of the twist rate of the bolt action norinco but it has got to be around there somewhere im thinking.
Just a little clarity is all.
Thanx