Down the bullet rabbit hole

[GetReal]

So I got a pretty good 6mm load, but gonna hafta switch lots. So I gathered a buncha data. I'm thinking the OAL factor is least important, then not sure of the order btwn bullet weight and / or length to ogive.

I think length to ogive *may* have about a 5/1000 window that may allow some wiggle room without opening groups up .... and bullet weight seems important. I think. Ironically, its the most consistent metric of these Berger bullets.

Also, I'm guessing if I move toa bullet with 4/1000 shorter bullet length....say 0.6555 to 0.6510, then I adjust my seating die 0.004 to get the same base to ogive ...theorettically.

End of the day, what happens at the range, on the target matters most.

But what conclusions would you draw from these different lot #'s ?

Mostly, how do you go about changing Lot #'s?

 

[Fuj]

End of the day, what happens at the range, on the target matters most.

And that sums it up.

 

[Bill Norris]

^^^ what he said.

 

[GetReal]

And that sums it up.

Yes, absolutely.

I'm just trying to find out if the numbers tell me anything.

 

[Bill Norris]

Yes, absolutely.

I'm just trying to find out if the numbers tell me anything.

I don't believe the numbers will tell you anything concrete until you put the loads on target.

 

[Dusty Stevens]

All itll take is a seating depth tweak. No need to write it down ahead of time

 

[dgeesaman]

Yes, absolutely.

I'm just trying to find out if the numbers tell me anything.

I’ve never found the numbers to matter much about whether a barrel will like that lot.

 

[calgarycanada]

FWIW, I keep my jump to lands the same. I haven’t had to adjust load anymore than that. Just my experience.

 

[K22]

I've shot a lot of 6mm, 85 BTHP's over the last 30+ years out of my various 243 Wins. I've found that the ogives of this bullet can vary quite a bit from lot to lot, but I've never been able to see it affect performance on target. This bullet, at least in my rifles, with IMR 4064, or Varget or IMR 4350 is extremely accurate, lot to lot.

As a comparison, the Nosler BT's, 90 grain are fairly consistent lot to lot and this bullet, while it shoots good enough in my rifles, isn't as accurate as that old Sierra 85 BTHP.

 

[AlNyhus]

Just because the bullet base-to-ogive differs in your new lot doesn't mean the case head-to-ogive will change by the same amount.

Try seating a new one and compare case head-to-ogive to your old lot and go from there. -Al

 

[mikecr]

I'm just trying to find out if the numbers tell me anything.

The numbers are the sum of too much to act on.
For example, [base to ogive] measure includes base length, bearing length, and ogive datum (affected by ogive radius). Each a different contributor to BC, and nothing proven to internal ballistics.
OAL adds nose length, which could sum to nothing in itself, but points to a potential meplat difference, which matters a lot to BC. But you'd have to measure the meplat to know.
Until your ogive radius is qualified, your ogive datum stands unqualified.

It's not easy to measure and consider these attributes with hard meaning.
So unless you're willing to, you might as well just shoot em and see how it goes.

 

[GetReal]

Just because the bullet base-to-ogive differs in your new lot doesn't mean the case head-to-ogive will change by the same amount.

Try seating a new one and compare case head-to-ogive to your old lot and go from there. -Al

That was one interesting outcome. I did as you said... and the 6/1000 bullet base to ogive difference didn't amount but to 1-2 / 1000 diff in case base to give loaded round difference.

 

[GetReal]

It's not easy to measure and consider these attributes with hard meaning.
So unless you're willing to, you might as well just shoot em and see how it goes.

True enuf. I'm still glad I did it....to educate myself on the differnces BETWEEN lots.

But yes....only testing can tell me which if any of these differences will actually matter.

 

[barefooter56]

So I got a pretty good 6mm load, but gonna hafta switch lots. So I gathered a buncha data. I'm thinking the OAL factor is least important, then not sure of the order btwn bullet weight and / or length to ogive.

I think length to ogive *may* have about a 5/1000 window that may allow some wiggle room without opening groups up .... and bullet weight seems important. I think. Ironically, its the most consistent metric of these Berger bullets.

Also, I'm guessing if I move toa bullet with 4/1000 shorter bullet length....say 0.6555 to 0.6510, then I adjust my seating die 0.004 to get the same base to ogive ...theorettically.

End of the day, what happens at the range, on the target matters most.

But what conclusions would you draw from these different lot #'s ?

Mostly, how do you go about changing Lot #'s?


View attachment 1387674

I seat a bullet from the new lot without adjusting the bullet seating stem first. Then compare the CBTO to the previous lots CBTO. If they are the same or within .003 either way ( + or -) I drop the powder charge 1/2 to 1 grain to compensate for more or less bullet length of the new lot being down in the cartridge case. Then work the load back up in 1/10th grain increments to get back on my velocity accuracy node. If you are seating by COAL I will try it this way also. UNLESS the bullet tip of the new lot is " bottoming out" in the bullet seating stem cavity changing the CBTO FROM ROUND TO ROUND IN THE BULLET SEATING PROCESS AND THE BULLET SEATING STEM CAVITY NEEDS DRILLED DEEPER this has worked for me

 

[GetReal]

I seat a bullet from the new lot without adjusting the bullet seating stem first. Then compare the CBTO to the previous lots CBTO. If they are the same or within .003 either way ( + or -) I drop the powder charge 1/2 to 1 grain to compensate for more or less bullet length of the new lot being down in the cartridge case. Then work the load back up in 1/10th grain increments to get back on my velocity accuracy node. If you are seating by COAL I will try it this way also. UNLESS the bullet tip of the new lot is " bottoming out" in the bullet seating stem cavity changing the CBTO FROM ROUND TO ROUND IN THE BULLET SEATING PROCESS AND THE BULLET SEATING STEM CAVITY NEEDS DRILLED DEEPER this has worked for me

That's pretty much exactly what Berger told me to do. Thx.

 

[AlNyhus]

That was one interesting outcome. I did as you said... and the 6/1000 bullet base to ogive difference didn't amount but to 1-2 / 1000 diff in case base to give loaded round difference.

First off, good for you for taking the initiative to dive a bit deeper into a subject that's misunderstood even by experienced accuracy hand loaders.

When comparing 'identical' bullets (ie: different lots/runs) that measure differently from bullet base-to ogive, there will be no difference in 'touch depth*' (expressed as a seated bullets distance to just touch the rifling*).... provided the bullets were pointed up in the same die.

The only difference will be how much bullet is in the case neck.

Once that concept is grasped, it's easy to see how 'touch depth*' is the point at which you work from.

Good shootin' -Al

 

[GetReal]

First off, good for you for taking the initiative to dive a bit deeper into a subject that's misunderstood even by experienced accuracy hand loaders.

When comparing 'identical' bullets (ie: different lots/runs) that measure differently from bullet base-to ogive, there will be no difference in 'touch depth*' (expressed as a seated bullets distance to just touch the rifling*).... provided the bullets were pointed up in the same die.

The only difference will be how much bullet is in the case neck.

Once that concept is grasped, it's easy to see how 'touch depth*' is the point at which you work from.

Good shootin' -Al

That's a GREAT reminder / explanation. Duh on my part. LOL

I've just hear SOOOO much handwringing about different bullet lots....

That aside.... most of my life exists in deep diving into what others would consider irrelevant and a waste of time. I'm just a curious person by nature. I don't mind a little hard work that might not "pay off" in ways that others think is worthwhile.

 

[Webster]

So I got a pretty good 6mm load, but gonna hafta switch lots. So I gathered a buncha data. I'm thinking the OAL factor is least important, then not sure of the order btwn bullet weight and / or length to ogive.

I think length to ogive *may* have about a 5/1000 window that may allow some wiggle room without opening groups up .... and bullet weight seems important. I think. Ironically, its the most consistent metric of these Berger bullets.

Also, I'm guessing if I move toa bullet with 4/1000 shorter bullet length....say 0.6555 to 0.6510, then I adjust my seating die 0.004 to get the same base to ogive ...theorettically.

End of the day, what happens at the range, on the target matters most.

But what conclusions would you draw from these different lot #'s ?

Mostly, how do you go about changing Lot #'s?


View attachment 1387674

Sounds like a varmint hunting rifle. You don't need to get OCD measuring things. Shoot a few groups and you know everything you need to know.

 

[mikecr]

Sounds like a varmint hunting rifle. You don't need to get OCD measuring things. Shoot a few groups and you know everything you need to know.

Well, maybe determine how far out you could put 5 shots into a varmint (From a benchrest, after sighters and warmups).
And then from there you should probably figure out a lot of real world things about varmint hunting.

 

[Webster]

Well, maybe determine how far out you could put 5 shots into a varmint (From a benchrest, after sighters and warmups).
And then from there you should probably figure out a lot of real world things about varmint hunting.

Figure out what real world things. I have been hunting GH since 1972.