Sierra MK Jump/Jam

eshorebwhntr

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Apr 20, 2011
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I've primarily only used Bergers since I've been reloading. All my rifles have shot best with minimal jump with the VLD and I've had good luck.

I'm loading up some 190 SMK's for a buddy in his 30 Hart. What is the rule of thumb with SMK's? (if there is one) Do they like jump, jam, impervious....

Thanks in advance for the help.
 

HodgdonExtreme

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In chambers with a short enough throat that any given Sierra bullet can even touch the lands, I start .020" off and that usually seems to work fine.

I try to remind myself a lot of rifles with exceptionally long freebore seem to shoot Sierras great, with a huge jump to the lands.
 

boone3380

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In chambers with a short enough throat that any given Sierra bullet can even touch the lands, I start .020" off and that usually seems to work fine.

I try to remind myself a lot of rifles with exceptionally long freebore seem to shoot Sierras great, with a huge jump to the lands.

+1

I've jumped them as much as .150 and they've shot well. My 300 WSM settled on .050 jump with 200gr SMKs but with 185 Berger VLDs it's only jumping .010
 

eshorebwhntr

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Apr 20, 2011
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In chambers with a short enough throat that any given Sierra bullet can even touch the lands, I start .020" off and that usually seems to work fine.

I try to remind myself a lot of rifles with exceptionally long freebore seem to shoot Sierras great, with a huge jump to the lands.

That's what I'm working with now, a long freebore. I think Hart of PA sort of sells that 30 Hart as a cookie cutter type package and assume that everyone will shoot their 180 NBT & RL19 recipe. Not my ideal combo so I thought I'd give the smk a try to start out. Hopefully the freebore isn't so much that I can't get the max potential out of the gun.
 

eshorebwhntr

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Apr 20, 2011
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In chambers with a short enough throat that any given Sierra bullet can even touch the lands, I start .020" off and that usually seems to work fine.

I try to remind myself a lot of rifles with exceptionally long freebore seem to shoot Sierras great, with a huge jump to the lands.

Good point. Hopefully holds true with this gun b/c I don't think I'll get to the lands with this gun and if I do it def won't be magazine.
 

JeffinTX

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SMK are relatively jump tolerant, having said that, I've found 0.020" off to be a common sweet spot for SMK 80 in .223/5.56 or SMK 155 in 308 Palma or SMK 175 in a bolt 308. The 168 SMK jumps just fine in the M1A, as does SMK 69/77 in .223/5.56
 

eshorebwhntr

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Apr 20, 2011
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I loaded up a few this weekend at magazine in a standard R700 to 3.600 OAL which was .145 jump. They shot decent at 200, roughly .75 moa. I've had the gun shoot the VLD less than .5 moa at 100 when seated .010 off the lands.

I loaded up 18 more smk's last night...3 batches of 6 each. Same charge with .010, .055, and .090 jump. Hope to shoot in the next week or 2 for comparison. I'll post results.