1/2, its not weight its length that counts, you SHOULD be able to shoot a 60 gr partition, or the 64 gr win power point. because they are short ogive flat base bullets so they are short for their weight, or if you can find them dead coyotes makes (or use to) a 7o gr thats the same length as a normal 55 gr, that'll be about max for a 12 twist.
RR
The bearing surface on the 69's BTHP is going to be much less per grain of weight than with the 55. You will have to push them pretty hard to get the velocity up enough to offset the lost stabilization with the heavier, less bearing bullet. I am not sure there is enough room to do it with the case and a 1/12 twist. With normal loads, the 69 is just not going to be able to spin fast enough to stabilize completely.
I hope that makes sense, at least thats the way I understand it.
Later,
Marcial
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You won't get a 69 grain SMK to stabilize at .223 velocities in a 12 twist barrel.
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A 55-gr Remington measures 0.619", while the 69-gr SMK measures 0.895". The key is not the length alone, it's how much of that length is in contact with the rifling, as has been mentioned already.
I'd like to hear how bearing surface of a particular bullet effects how fast a bullet is spun as it travels down the barrel.
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makes sense to me..the more surface friction, the more it slows. how much, i have no idea.
since your asking..i imagine bearing surface is the part that dont touch the rifling?
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223 12twist heaviest bullet?
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