im not sure if this topic has been covered yet, I tried running a search, but got either nothing or everything. If it has, and somebody can post the link, Ill let this thread die an early death.... On to the topic.
Ive been reading/thinking about the culling process used by many benchrest shooters. supposedly the best way to make the smk's shoot with the custom bullets is selective culling, and grouping the like bullets.
I have been shooting 220SMKs for a couple months now at 1350, and I have notticed a marked trend towards a 2 and 1 group, or 3 and 2 group, depending on 3 or 5 shots.
I just finished sorting a box and a half of these bullets. here is what I found.
lot#001830853
4 @.674
8 @.674
3 @.675
24 @.676
13 @.677
the other was a full box from
lot#001831067
1 @.673
10 @.674
10 @.675
46 @.676
32 @.677
1 @.678
In the next few days im going to find some time to sort the larger samples within a given length for weight as well, then shoot these to see if I can shrink those groups on down.
Any body out there sorting bullets by bearing surface or by any other method than weight?
I had an earlier post on this very subject but I couldn't find it.
Yes, there is an ogive variance in custom bullets and it can make a big difference at long ranges. I noticed that bullets measuring .002" difference in ogive length hit about 2' 6" higher at 1785 yards out of my 6.5-.284! So now I measure every bullet(before and after seating) and put them into rows in my ammo box according to ogive length. The .002" diff didn't make too much difference at 1000 yards, but it was still noticeable on a calm day.
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basically the same setup im using. Im using twin comparitors for bearing length measurement. Much faster than using my neco, and youre right, just as accurate if you use cosistant pressure.
maybe ill go back and do some measuring to see where the extra length is... compare the bearing surface inconsistancies vs the base to ogive length.
My rifle keeps "wanting" to shoot smaller groups at that range, I can usually get a few in 5"-8", but one always manages to open it to 14"-20". Very annoying. Then I have to stay up till 2am trying to figure out what im missing...
Ive gotta figure out how to weed that one stinking bullet out, that way I can get some sleep!
I sorted some .338 300SMK by bearing surface. They were all one of two lengths, with one odd one a couple thou longer.
I tested the accuracy, but had also checked concentricity, neck-turned and a few other things for the first time.
I was very happy with the groups, but can't say how much was the bearing length sorting.
I also trimmed meplats.
FWIW--I also use the dual SP comparitors, but a local buddy that builds his own perfectly little precisie bullets is telling me i might be better off sorting by OAL.
might try both on paper and see what happens.
also FWIW, i have found my case of lapua 105 scenars to be EXTREMELY close in BS length--even better than customs i have measured.
and by extremely close i mean 200 bullets broke down into 4 BS lengths (.543-.546 IIRC) with only 3!! bullets outside of .544"-.545"
the other 197 were pretty evenly split between .544"BS and .545"BS
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