So close, and yet....

J-B welder

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I have two different 85 gr HPBT bullets, about 50 of each. One bunch is factory fresh, the other is pulled. I took a sample of 10 from each and weighed them and measured them, and found that the factory bullets all weighed 84.9 grains and varied in base to ogive length by only 0.0005". The pulled bullets weighed between 84.9 and 85.3 grains, and were around 0.0090" shorter from base to ogive than the virgin bullets. I say "around" because they varied in length from base to ogive by 0.0025".

My question is this: Knowing that I will probably get the advice that any time I change a single component I should start low and work my way up again, would an accurate load developed with the pulled bullets at least give me some useful information about what will work with the factory fresh bullets, or are there other variables about bullet construction that would render any such info useless?
 

Bob Wright

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I have two different 85 gr HPBT bullets, about 50 of each. One bunch is factory fresh, the other is pulled. I took a sample of 10 from each and weighed them and measured them, and found that the factory bullets all weighed 84.9 grains and varied in base to ogive length by only 0.0005". The pulled bullets weighed between 84.9 and 85.3 grains, and were around 0.0090" shorter from base to ogive than the virgin bullets. I say "around" because they varied in length from base to ogive by 0.0025".

My question is this: Knowing that I will probably get the advice that any time I change a single component I should start low and work my way up again, would an accurate load developed with the pulled bullets at least give me some useful information about what will work with the factory fresh bullets, or are there other variables about bullet construction that would render any such info useless?
I would just shoot them in different groups. A little science experiment for groups and speed. I wouldn't start over and waste ammo and components. If the inferior ones scatter, they're plinking bullets.
 

J-B welder

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I would just shoot them in different groups. A little science experiment for groups and speed. I wouldn't start over and waste ammo and components. If the inferior ones scatter, they're plinking bullets.
Well, yeah. I'm sure the pulls will shoot less consistently than the factory fresh bullets.

I guess what I'm asking is if the pulls were more uniform, would a 0.5% difference in weight and 1% difference in length translate to radically different trajectories between the two, or is there more to it than just those numbers? Would the performance I get from the pulls help me avoid the component waste you refer to by reducing the range of charges and seating depths I might try for the factory pills?
 

Bob Wright

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Yes. Shoot the same level of powder and just see if there is any degradation in group size between the two. Run 2 sets of 10 for both bullets. I would guess there will be some small variation but not enough for hunting.
Of course run a chronograph on both for velocity changes. I wouldn't want to waste any components during this ammo shortage.
 

QuietTexan

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Are these the same make/model of 85gr HPBT bullets? Or is the 85gr just coincidental and they're two drastically different bullets?

If they're the same make and model, this is just a lot change for the same component, not a "new" component that you have to work back up for. Normally for a lot change I would say keep the same seating depth, and:
  • If you aren't at max, go 0.1-0.2gr high and low around your change (or whatever an appropriate ~1% change would be)
  • If you're at max, drop 0.2-0.4gr below (two steps down) and shoot back up to it
  • 9-15 shots to re-verify you're in the node still
If you only have 50 and aren't at the max I would load using the same data as the previous lot. If you are at the max... that's your call based on what signs you're seeing on the brass. Big difference between "book max" and seeing spooky signs.
 
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MagnumManiac

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I have never found a weight difference show up on target.
I HAVE found a difference on target with bullets that did not have the same CBTO.

Cheers.
 

J-B welder

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Are these the same make/model of 85gr HPBT bullets? Or is the 85gr just coincidental and they're two drastically different bullets?

If they're the same make and model, this is just a lot change for the same component. Normally for a that I would say keep the same seating depth, and:
  • If you aren't at max, go 0.1-0.2gr high and low around your change (or whatever an appropriate ~1% change would be)
  • If you're at max, drop 0.2-0.4gr below (two steps down) and shoot back up to it
  • 9-15 shots to re-verify you're in the node still
If you only have 50 and aren't at the max I would load using the same data as the previous lot. If you are at the max... that's your call based on what signs you're seeing on the brass. Big difference between "book max" and seeing spooky signs.
I don't think they are the same make and model. The person I got the pulls from didn't know what make they were. I figured I could at least load them for trigger time practice.

I'm new at this and had started working up a hunting load for the factory bullets but seem to be spinning my wheels, not getting closer to a good load. So I thought if the pulls measured near enough to the factories I might be able to use them to get in the ballpark and prevent wasting too many more of the good ones.
 

J-B welder

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I have never found a weight difference show up on target.
I HAVE found a difference on target with bullets that did not have the same CBTO.

Cheers.
Understood, but I could load them all to have the same CBTO. I think the difference I'm measuring between the bullets (not the cartridges) means the ogives are shaped differently, though. Thought that might affect POI.
 

MagnumManiac

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Yes definitely will change POI if the CBTO is different and you don’t adjust for it.
I ran into this, was way outta the nose and I didn’t know why...worst match I had in quite a while. I always load more than needed, so when I got home I measured the ogive from case base and it was a full .020” shorter...WTH?
Different Lot # and different ogive length.
I’ve never failed to measure every batch since.

Cheers.
 

Mikecr

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or are there other variables about bullet construction that would render any such info useless?
USELESS
A BTO measure includes base length, bearing length, and ogive datum(as affected by ogive radius). You don't know which is contributing to what in summation -for each and every bullet in measure.
So you have nothing actionable to consider with any one bullet, or either group of bullets.
 

J-B welder

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USELESS
A BTO measure includes base length, bearing length, and ogive datum(as affected by ogive radius). You don't know which is contributing to what in summation -for each and every bullet in measure.
So you have nothing actionable to consider with any one bullet, or either group of bullets.
Thanks for the feedback.
 
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