Bullet Ogives Change with Lot Numbers

[QuietTexan]

Anyone else frustrated? I don't understand how manufacturers can't control something like this better - it is pretty critical.

They run a lot of presses. There are multiple die sets in their popular calibers. Tooling wears over time. It's something to be aware of and not upset about.

When I ordered custom benchrest bullets the company I used was very upfront with the differences between their hand pressed and machine pressed bullets, the differences that result, and the possible ramifications of them. I actually use machine pressed bullets because the variances they were holding, while not as good as possible, were more than good enough for my use.

At least Berger keeps bullets in a lot coming from one press, they usually show a peak around a single bullet length. Sierra often shows two lengths inside one lot - either bad dies or mixing press output. Hornady has shown a wider spread inside a lot, but groups around a single length instead of two like Sierra. I haven't bothered with sorting Barnes Match Burners, the one time I tried it was tough to even get enough of the same length to sort by.

Litz's Vol 3 showed a lot of data behind his recommendation to sort by bullet length to capture multiple inconsistencies, instead of measuring by weight, BTO, bearing surface, etc. Interesting read. I gave up on weight sorting bullets, I'll still sort by length inside a single lot.

I sit down with calipers and a set of 13 parts bins. I start with 10-20 bullets, write their lengths on sticky notes, and sort out another 100 or so. By then I can normally tell where the center of the distribution is going to be, tag one bin as 0.000", set my calipers off of those bullets. The other 12 bins have permanent +0.001", +0.002" etc labels all the way out to +/-0.006+". Rock through the remainder of the lot, very fast to sort because the calipers spit out easy numbers I don't have to really think about. Usually the +/-0.006" bins are empty, but I have caught some very very off bullets before. Never wrong caliber, but probably wrong model. Pack them back into bags marked with their variance and count, into their original boxes.

This is why I buy as many same-lot bullets as I can. Last 6.5-284 barrel I ordered shipped with 2000 153.5gn Bergers, same lot numbers.

But correct me if I'm wrong, but if you are measuring to the Ogive thats the first contact point for the lands.

I agree that you would need to adjust the die, but the load will be fine as long as you maintain the BTO number. Thats all I was saying.

That's a common misconception. Bullet comparators, unless cut and measured to be accurate, typically measure a point forward along the meplat of the actual land diameter for the caliber. My Hornady comparators aren't even round, much less cut to an exact diameter.

Something you can do is lock a pair of calipers at at .300" for a .308 bullet, use the calipers to scribe a ring around the meplat, then compare to where your particular bullet comparator is landing. My Hornady set is at best +/-0.002". Some are better, some are worse. This is why BTO measurements are always relative to the individual measuring tool use, whereas COL, even with varied meplat length, is usually closer to repeatable.

 

[LRNut]

And you confirmed there's nothing interfering with your measurements? It's 100% just an actual variance in the dimensions of the bullet?

Not trying to be a jerk, just trying to confirm the actual problem.

Measuring ogives with a comparator is pretty simple. I check my OALs using a comparator for every LR round I load, and I have often noticed I need to tweak my seating die.

 

[LRNut]

They run a lot of presses. There are multiple die sets in their popular calibers. Tooling wears over time. It's something to be aware of and not upset about.

When I ordered custom benchrest bullets the company I used was very upfront with the differences between their hand pressed and machine pressed bullets, the differences that result, and the possible ramifications of them. I actually use machine pressed bullets because the variances they were holding, while not as good as possible, were more than good enough for my use.

At least Berger keeps bullets in a lot coming from one press, they usually show a peak around a single bullet length. Sierra often shows two lengths inside one lot - either bad dies or mixing press output. Hornady has shown a wider spread inside a lot, but groups around a single length instead of two like Sierra. I haven't bothered with sorting Barnes Match Burners, the one time I tried it was tough to even get enough of the same length to sort by.

Litz's Vol 3 showed a lot of data behind his recommendation to sort by bullet length to capture multiple inconsistencies, instead of measuring by weight, BTO, bearing surface, etc. Interesting read. I gave up on weight sorting bullets, I'll still sort by length inside a single lot.

I sit down with calipers and a set of 13 parts bins. I start with 10-20 bullets, write their lengths on sticky notes, and sort out another 100 or so. By then I can normally tell where the center of the distribution is going to be, tag one bin as 0.000", set my calipers off of those bullets. The other 12 bins have permanent +0.001", +0.002" etc labels all the way out to +/-0.006+". Rock through the remainder of the lot, very fast to sort because the calipers spit out easy numbers I don't have to really think about. Usually the +/-0.006" bins are empty, but I have caught some very very off bullets before. Never wrong caliber, but probably wrong model. Pack them back into bags marked with their variance and count, into their original boxes.

This is why I buy as many same-lot bullets as I can. Last 6.5-284 barrel I ordered shipped with 2000 153.5gn Bergers, same lot numbers.



That's a common misconception. Bullet comparators, unless cut and measured to be accurate, typically measure a point forward along the meplat of the actual land diameter for the caliber. My Hornady comparators aren't even round, much less cut to an exact diameter.

Something you can do is lock a pair of calipers at at .300" for a .308 bullet, use the calipers to scribe a ring around the meplat, then compare to where your particular bullet comparator is landing. My Hornady set is at best +/-0.002". Some are better, some are worse. This is why BTO measurements are always relative to the individual measuring tool use, whereas COL, even with varied meplat length, is usually closer to repeatable.

To your point, I learned the hard way that you can't take two different Hornady comparators and assume they are they are the same. I have the Hornady comparators in both CO and PHX. I developed a load in CO but grabbed the wrong box of bullets when I went to Phoenix. No big deal I thought, I have the load data on my iPhone. Wrong. Even though I matched the comparator OAL in Phoenix to what I had developed in CO, when I got back to Colorado with some rounds loaded in Phoenix, they had a different comparator OAL. It was only a few thousandths, but it wasn't the same.