Bullet Variation

[mtang45]

I'm working on a 7mm STW load for 180gr VLD Bergers and am trying to sort to eliminate as much variation as possible. I've sorted by weight, and right now I'm sorting again by the length of the bearing surface. What other dimesions should I consider measuring? Total length? Base to ogive? Nose to ogive? Or other? A person could go crazy sorting out all the possible variables.

By the way the range I'm getting is .12mm total variation on the bearing surface, and .4gr total variation on the bullet weights. Does this sound excessive, normal or good?

 

[RonAKA]

I've sorted by weight, and right now I'm sorting again by the length of the bearing surface. What other dimesions should I consider measuring? Total length? Base to ogive? Nose to ogive? Or other? A person could go crazy sorting out all the possible variables?

I have done sorting by weight but found in 68 grain Berger bullets I'm only seeing a variation of 0.05 grains spread. I think a work up of the ballistics would show the weight effect to be insignificant. Total length I think would be a waste of time, as the tip can be all over the place, and I think has little effect. Bearing surface length may be worthwhile. I have not tried it yet, but plan to. I have also measured body diameter and sorted on that. It might help. Variation in Bergers is not much but I have seen up to 0.0003" extreme spread.

 

[mtang45]

Just a followup. I measured all 100 bullets in the box and found the bearing surface to vary from 16.25mm to 15.91mm. Weight was fairly consistant and varied from 179.6gr to 180.1gr.

The majority of the bullets fell into three groups 16.2mm +- .02, 16.15mm +- .02, 16.10mm +- .02. I did have three greater than 16.22 and 5 less than 16.08.

Most bullet weights fell within 180gr +- .1 with about 10 weighing less than 179.9, none were over.

This is the first time I have checked Berger bullets, is this normal variation?

 

[Shynloco]

I've sorted by weight, and right now I'm sorting again by the length of the bearing surface. What other dimesions should I consider measuring? Total length? Base to ogive? Nose to ogive? Or other? A person could go crazy sorting out all the possible variables?

I have done sorting by weight but found in 68 grain Berger bullets I'm only seeing a variation of 0.05 grains spread. I think a work up of the ballistics would show the weight effect to be insignificant. Total length I think would be a waste of time, as the tip can be all over the place, and I think has little effect. Bearing surface length may be worthwhile. I have not tried it yet, but plan to. I have also measured body diameter and sorted on that. It might help. Variation in Bergers is not much but I have seen up to 0.0003" extreme spread.

RonAKA,

I know you do alot of testing of all sorts. And I see you use 68 gr bullets. Just out of curisoity, have you weighed and tested any other manufactured 68 gr bullets and looked for variances in their weight? If so, which manufacturer has the least deviation? Thx

Alex

 

[RonAKA]

RonAKA, I know you do alot of testing of all sorts. And I see you use 68 gr bullets. Just out of curisoity, have you weighed and tested any other manufactured 68 gr bullets and looked for variances in their weight? If so, which manufacturer has the least deviation? Alex

Alex I have measured a few. Here are the results:

Bullet Weight/Type - AVG Weight - ST DEV WT - AVG Body Dia. - ST DEV Dia

Berger 62 Target - 61.995 - 0.02838 - .24283 - .00009487
Berger 68 Target - 67.965 - 0.02415 - .24269 - .00003162
Bart's Ultra 68 - 68.030 - .04830 - .24274 - .00005164
Sierra HP 75 - 74.930 - .03496 - .24260 - .00000000

Lowest ST DEV in bold. Spreadsheet attached. The Lowest standard deviation for weight are the Berger 68's. They also shoot the best with 3 shot groups in the .1's. However next lowest are the Berger 62's. They are the worst bullet I shot and I can't get three shot groups under 1.4".

On body diameter, the 10 Sierra 75's I measured were exactly the same diameter, so zero standard deviation. All bullets are flat based. Both the Berger and Bart's have a significant pressure ring, and the Sierras have none that I could measure. Have not loaded any of the Sierras yet, so it will be interesting to see how well they shoot.

Based on measurements, I suspect Sierra form their bullets differently than Berger and Barts. Must be a reason why Sierra has no pressure ring...

 

[jonbearman]

Do you guys have any hair left on your heads?LOL LOL Wow that takes alot of concentration to figure it all out.I dont even know how to measure the ogive.

 

[HolyMeekrob]

In all the reloading and shooting I've done I've never found bullet sorting of any kind to make a discernible difference that can be shown to fall outside normal human error (that might be a redundant statement but I'm out for specificity and not efficiency), so I generally consider it a waste of time. But that could be less a statement about the usefulness of bullet sorting and more a statement of my talents in reloading and shooting.
Either way I love reading German Salazar's journal and find he's spot on about everything. I also think he takes a very practical and efficient approach to reloading, so I'd heed his word. Anyway he's talked about bullet sorting at least twice. Here's one and the other should be linked at the bottom:
http://riflemansjournal.blogspot.com/search?q=bullet+sorting

 

[Heavies]

Very good read. I like very much how German does things.

So, what exactly are you doing when you use your comparator?
Do you set all the bullets to the same depth in relation to the ogive? Or do you just set up a dummy round and make the rest close? Does the relation of the bullet to the lands make the most difference in accuracy, or is the uniform depth intrution into the case make that accuracy improve?
;D

 

[Bob3700]

I sort bullets by bearing surface length. The weight variation follows the variation in bearing surface length so I don't wt. sort.

The bigger the bullet the more variation you see. SMKs have more than a Berger but the variation in Berger's is still there.

If you are shooting 7mm 180s, the present price is approaching $50 a box. For that kind of money, I don't feel that I should have to sort anything!

SMKs in 6mm (107s) once sorted and pointed will shoot with the best that anyone is producing today. In fact, my highest X counts have been with SMKs.

At 600 yds, sorting will give you groups that are more round and even. Less flyers. At 1000 yds everything matters. The other aspect is that I enjoy precision reloading and don't mind spending the time assembling ammo that gives me confidence when I pull the trigger.

If you think it matters, it does!

Bob

 

[6BRinNZ]

Brian Litz has an interesting section on bullet variation and potential affects in his book, he makes some suggestion as to the % of variation that matters, my interpretation is that you need to look at the differences as a percentage to obtain meaning, having said that everything exactly the same is best.

It appears as though the shooting application and the bullet type selected drives the effort vs reward of bullet sorting.

I definitely agree with Bob, going shooting (whatever type) thinking that you have every thing sorted gives a lot of confidence, only experience tells you that some of the prep probably didn't matter. LOL.

Good luck!