Seating depth for SMK

7

7BR

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Any opinions & advise would be of help, thanks.

I have a center grip xp-100, with a 10 twist Douglas barrel & 36x scope in 7 br. I enjoy shooting 100 yard BR, the ( gun ) will shoot tiny groups with 150 gr. SMK. Thats what the gun likes. Now trying to shoot a rig like this is hard to do consistantly, so I`m still playing around with seating depths trying to shrink my groups. Bullets that heavy, cause it to jump off the bench, so I got some 130 gr. SMK to try. I was told a 10 twist would work for 130 gr. Would the seating depth be the same for the lighter bullet ? I know i`ll have to work up a load, but what are the opinions on the depth. I ask because being so hard to be consistance, it takes a lot of shots to find out what works best. Thanks for the help
 
First of all, I doubt moving from 150 to 130 grain bullets will significantly reduce the "jumping off the bench" phenomena. But that's somewhat subjective, so who knows?

Secondly, while the same seating depth with the 130s as you use with the 150s might be a good place to start, seating depth is one of those variables you just have to test with each change, along with powder, and for some, neck tension. Yes, they all interact.

Shoot three shot groups to rule things out. If three shots are bad, more won't make it any better. If you can't shoot consistently, you can't test, so take your time & be careful. Among the three shot groups, when a couple start to look good, that's time for a 5-shot group. And to evaluate the best of the 5-shoters, either 5 five shot groups, or a 10-shot group or two. I prefer the 10-shot group, but that and a couple bucks will get you coffee these days.
 
Just because lighter bullets don't need a 10 twist doesn't mean they won't shoot with it. My 7BR Rampro pistol with a 10 twist Schnieder shoots Speer 115 Gr HPs into tiny groups. Nothing lost by trying. It also shoots 120 Noslers well. I start with seating to lightly touch the lands and usually stay close to that.

Scott
 
Might want to try a brake to settle down the jump, I've got an xp with a 14 and 8 twist barrels and a brake on both of them. The brake knocks 70% of the hop out.
 
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