Coal/cbto

[MeatBuck]

Seated some Berger elite hunters a couple weeks ago and had fits getting a dozen loaded to the same coal. Had to adjust mic top on each one and ran several in too far while the one before was perfect. Pulled and reseated those so all were at 3.080”(mag length).
Now measuring the cbto I’ve got several different measurements and only two are the same. They range from 2.2975”-2.3090” when using Sinclair comparator.

Is this difference excessive or am I just trying to be too much of a perfectionist?

I have but have not used my vld stem but that will only maybe seat them more accurately with less fooling with mic top but wont change the variation I’m seeing in cbto right?

 

[Tahoe1305]

Not to say I’m an expert reloader, however I reload to CBTO because the way I understand it that is what matters (where the thickest part of the bullet is going to hit the rifling).

This takes out the variability in the tips and finishing process and minimizes jump differences.

If this was done you would likely expect the COAL to have the variances you describe but they in theory would shoot better.

Hope that helps.

 

[Brendan]

Don't use COAL except to make sure loaded rounds will fit in your mag. After that, everything should switch to CBTO using your comparator.

That's too much variation for me. I have found though that there's a technique to getting consistent readings - if you measure the same loaded round multiple times, are you getting the same reading?

 

[nhyrum]

Coal will vary because the die pushes on the ogive, and bullet shapes aren't identical and length can vary, especially with otm bullets. Seat and measure cbto, that's the critical dimension anyway.

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[MeatBuck]

Don't use COAL except to make sure loaded rounds will fit in your mag. After that, everything should switch to CBTO using your comparator.

That's too much variation for me. I have found though that there's a technique to getting consistent readings - if you measure the same loaded round multiple times, are you getting the same reading?

Ya same reading

 

[Brendan]

I'd probably check first to make sure bullets are not bottoming out in your seating stem. Then, things like making sure dies are set up correctly with a little cam-over, a mandrel for consistent neck tension and using some dry-lube on your brass.

 

[MeatBuck]

I don’t have this issue with the hammer bullets when I load to coal, the cbto is very close to the same.
this being the reason for my question about the Berger’s.

 

[Brendan]

Bottom line: You shouldn't be loading to COAL. Load to CBTO.

 

[MeatBuck]

I'd probably check first to make sure bullets are not bottoming out in your seating stem. Then, things like making sure dies are set up correctly with a little cam-over, a mandrel for consistent neck tension and using some dry-lube on your brass.

There’s a contact ring on them from stem so don’t think they are bottoming out.
I run mandrel to set neck tension.

 

[MidGAHunter]

Bottom line: You shouldn't be loading to COAL. Load to CBTO.

^^^ This

 

[Brendan]

Effects of Cartridge Over All Length (COAL) and Cartridge Base To Ogive (CBTO) - Part 2

The first half of this article focused on the importance of COAL in terms of SAAMI standards, magazine lengths, etc. There is another measure of length for loaded ammunition which is highly important to precision.

bergerbullets.com

There is another aspect to knowing your CBTO when checking your COAL as it pertains to performance. With good bullets, tooling, and carefully prepared cases you can easily achieve a CBTO that varies less than +/- .001” but your COAL can vary as much as .025” extreme spread (or more with other brands).

 

[N2TRKYS]

I only load to COAL. I’ve never had a reason not to.

 

[Brendan]

I only load to COAL. I’ve never had a reason not to.

If it's worked for you, great, but you're potentially adding in variability in jump / distance to the lands that you don't need to. If you're curious, read the article linked above from Berger that explains it. And it certainly can cause issues in certain scenarios.

@MeatBuck - The reason it probably works with Hammer Hunters is that they're an individually CNC machined / small volume all copper bullet. Much easier to to keep bullet dimensions exact that way.

 

[N2TRKYS]

If it's worked for you, great, but you're potentially adding in variability in jump / distance to the lands that you don't need to. If you're curious, read the article linked above from Berger that explains it. And it certainly can cause issues in certain scenarios.

@MeatBuck - The reason it probably works with Hammer Hunters is that they're an individually CNC machined / small volume all copper bullet. Much easier to to keep bullet dimensions exact that way.

Bergers have been the most inconsistent bullets(length and weights) I’ve measured compared to the Noslers that I use. Their overall length was more consistent than measuring to the ogive.

A better use of my time has proven to be weight sorting bullets than worrying about measuring to the ogive.

So, excuse me if I don’t care to read what Berger has to say. Lol

 

[MeatBuck]

Thanks for replies.

I read that article but either missed or forgot that part as I’ve read seemingly a thousand articles recently.

I measure both coal and cbto to ensure I’m not into the lands but will just scratch coal measurement and likely single feed the Berger’s.
I’ll keep doin what I’m doin with the hammers as it seems to be working.

 

[Brendan]

A better use of my time has proven to be weight sorting bullets than worrying about measuring to the ogive.

How is it a "Better Use of Time" when both methods take exactly the same amount of time, and one gives more reliability on the measurement that matters?

I think it's one of those scenarios - do whatever's working for you. Hell, I've had awful luck with Nosler and am doing whatever I can to stay away from them from here on out.

 

[nhyrum]

How is it a "Better Use of Time" when both methods take exactly the same amount of time, and one gives more reliability on the measurement that matters?

I think it's one of those scenarios - do whatever's working for you. Hell, I've had awful luck with Nosler and am doing whatever I can to stay away from them from here on out.

Weight consistency matters. You can point and trim meplats. Easy. I'd spend my time wight sorting, then trim and point the meplat vs sort by bearing surface. It's ignorant to say someone else's approach is stupid. More than one way to skin a cat


Now, the best of both worlds is to buy CNC machined bullets, like cutting edge. Identical (for all practicality) weight and measurements. Easy. Done and done
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[mvrk28]

I don’t have this issue with the hammer bullets when I load to coal, the cbto is very close to the same.
this being the reason for my question about the Berger’s.

hammers are milled on a CNC lathe so they should be very consistent, that being said best practice is always to load to CBTO. You really don’t care about what’s happening from ogive to meplat.

 

[mvrk28]

If it's worked for you, great, but you're potentially adding in variability in jump / distance to the lands that you don't need to. If you're curious, read the article linked above from Berger that explains it. And it certainly can cause issues in certain scenarios.

@MeatBuck - The reason it probably works with Hammer Hunters is that they're an individually CNC machined / small volume all copper bullet. Much easier to to keep bullet dimensions exact that way.

You’re nailing all the answers, can’t help it when people don’t listen.

 

[mvrk28]

Weight consistency matters. You can point and trim meplats. Easy. I'd spend my time wight sorting, then trim and point the meplat vs sort by bearing surface. It's ignorant to say someone else's approach is stupid. More than one way to skin a cat


Now, the best of both worlds is to buy CNC machined bullets, like cutting edge. Identical (for all practicality) weight and measurements. Easy. Done and done
Sent from my SM-G975U using Tapatalk

You are wasting your time to weight sort any cup and core bullet and your method IS stupid. There is no universe where it makes sense to weight sort in lieu of seating to CBTO and to say it’s a waste of time to seat to CBTO shows how little you know about the process.

PLEASE tell me how spending the time to weight sort and tip meplats makes more sense than seating to CBTO and being done with it. You are using the caliper one way or another.

also for the heck of it I just weighed 5 140 gr VLDs, 4 of the 5 came back at 140.0 gr and one came back at 140.1 gr. Weighed 5 124 gr hammer hunters and the weights ranged from 123.7 to 124.1.