Bullet Sorting

[300 RUM]

I would like to hear from the people who sort their bullets by ogive to base and/or weight.

The question is:
Does it really matter if you sort or not? If so is there a choice preference between the two?

 

[ridgeway]

I sort boat tail to ogive just because I obtained a Mark King comparator at no cost. I used to sort base to ogive. Honestly, either way will work just fine. Sorting does make a difference especially if you plan on trimming and pointing. Sierra especially. Berger is much better in uniformity. The reason I sort is to keep things consistent. I trim and point in sorted lots because tooling adjustment may be warranted from lot to lot.

I do not sort by weight.

 

[300 RUM]

I just sorted 250 @ 175 SMk and had a spreed from .640 to .669.. So how you you suggest I group them?

 

[Scott Harris]

I did a small experiment at 1000 yards recently . Fired six shots in a row at the end of a match string. 3 shots had a short bearing surface length and three shots had a bearing surface length .009" longer. I use the Tubb comparators at both ends of the bullet to get total bearing surface length (BSL). I alternated short, long, short and made no scope or aiming adjustments. The wind was from 4 o'clock and slowly increasing during these 6 shots...don't think they had any effect on elevation. Here is the result I got:

The odd numbered shots have short BSL and the even ones have long BSL. This was a small test at long range. But the results seem to clearly point to a relationship between bearing surface length and impact elevation.

I'm still collecting data and these results have caused me to come up with a bunch of new questions to explore. Is this effect seen at shorter distances? What is the maximum variance that effectively has no/minimal elevation dispersion? Do base-to-ogive and BSL have a strong correlation? Strong enough so that the quicker base-to-ogive measure can effectively substitute for a BSL measure? Are some brands of bullets better than others with this measurement? Lots of work to do, but some of my preliminary testing indicate:

1. All brands of bullets show BSL variation. When comparing Sierra, Hornady, and Berger, there were good and bad samples from each company. Each brand showed a standard bell curve pattern of variance. The amount of variance seems to be more about the lot # and type of bullet than which company you select. I'm collecting lots of samples and will put them into a spreadsheet to calculate SDs.
2. Only did a small test (like 100 bullets): measured both BSL and base-to-ogive on the bullets. I did not see as strong of a correlation as I expected. Using only this small test result, I would conclude that you need to measure BSL and base-to-ogive does not capture all the variance in bearing surface.

That's my .02 for now.

 

[300 RUM]

I did a small experiment at 1000 yards recently . Fired six shots in a row at the end of a match string. 3 shots had a short bearing surface length and three shots had a bearing surface length .009" longer. I use the Tubb comparators at both ends of the bullet to get total bearing surface length (BSL). I alternated short, long, short and made no scope or aiming adjustments. The wind was from 4 o'clock and slowly increasing during these 6 shots...don't think they had any effect on elevation. Here is the result I got:

The odd numbered shots have short BSL and the even ones have long BSL. This was a small test at long range. But the results seem to clearly point to a relationship between bearing surface length and impact elevation.

I'm still collecting data and these results have caused me to come up with a bunch of new questions to explore. Is this effect seen at shorter distances? What is the maximum variance that effectively has no/minimal elevation dispersion? Do base-to-ogive and BSL have a strong correlation? Strong enough so that the quicker base-to-ogive measure can effectively substitute for a BSL measure? Are some brands of bullets better than others with this measurement? Lots of work to do, but some of my preliminary testing indicate:

1. All brands of bullets show BSL variation. When comparing Sierra, Hornady, and Berger, there were good and bad samples from each company. Each brand showed a standard bell curve pattern of variance. The amount of variance seems to be more about the lot # and type of bullet than which company you select. I'm collecting lots of samples and will put them into a spreadsheet to calculate SDs.
2. Only did a small test (like 100 bullets): measured both BSL and base-to-ogive on the bullets. I did not see as strong of a correlation as I expected. Using only this small test result, I would conclude that you need to measure BSL and base-to-ogive does not capture all the variance in bearing surface.

That's my .02 for now.

WOW, now thats Black and White!

Assuming thats a scale F class target your about 7-8" change in elevation at only .009. I would then say one need to group no more then .003 difference to get good consistent accuracy.

Oh Also I'm going to shoot these 175 SMK's the OD meassured .3055-.306, do you have any you can measure to cross check the OD for me.

I going to make a gauge *(Double ended) to meassure the BSL and would like to get a good idea of avg dia.