Coal/cbto

[Clucknmoan]

Your seating stem actually contacts the bullet forward of the ogive, or at least all of them I’ve measured. Some seating stems just don’t work well with certain types of bullets because of their shape. It’s not that they touch or bottom out at the bullet tip. The seating stem can actually bite into or grab the bullet on your upswing, moving it out. It’s not much and I’m not saying that’s what’s happening, but it can especially with light tension.

Can you see a ring or indent on your bullet between the ogive and the tip after they are seated? How many times have you fired this brass?

 

[MeatBuck]

Not sure what you mean by won’t effect BTO. The BTO measurement is taken below where the seating stem contacts, so by bottoming it out it should effect BTO. Or am I misunderstanding what you are saying.
It really isn’t a bad idea to bottom out a couple times anyway. If I am getting bad runout, I will bottom the press out, then rotate the case 1/3 or 1/2 turn or so and stroke it again. Sometimes it helps with runout if you have a case or die that sits wonky in the press.

Because the coal measurement doesn’t matter at that point just the cbto which should always remain consistent and that was where the difference I was seeing in the loaded rounds came from not from cbto. If I hadn’t dicked with the mic top between rounds trying to get consistent coal the cbto would have stayed the same. Or I would be chasing the seater stem troubles but I’m not because I haven’t loaded anything to cbto yet.
the 3.080” coal would actually be 2.3775” cbto with these hammers the cbto varies from 2.3760” to 2.3780” and with the Berger’s they were way worse when coal is same. I’m no longer going to measure coal to set die only to check mag fitment.

 

[MeatBuck]

Your seating stem actually contacts the bullet forward of the ogive, or at least all of them I’ve measured. Some seating stems just don’t work well with certain types of bullets because of their shape. It’s not that they touch or bottom out at the bullet tip. The seating stem can actually bite into or grab the bullet on your upswing, moving it out. It’s not much and I’m not saying that’s what’s happening, but it can especially with light tension.

Can you see a ring or indent on your bullet between the ogive and the tip after they are seated? How many times have you fired this brass?

Slow down with the questions as your missing info and asking questions I’ve already answered.

yes very slight ring on bullet ABOVE the ogive.

like I said in the last post, not even to once fired state with this Norma brass.

 

[Cahunter805]

Meat
Sounds like you have it figured out. Use CBTO and I bet you see pretty consistent lengths from your die. I assume it’s a Redding die? Install the VLD seater stem and proceed to load to CBTO.

 

[Clucknmoan]

Slow down with the questions as your missing info and asking questions I’ve already answered.

yes very slight ring on bullet ABOVE the ogive.

like I said in the last post, not even to once fired state with this Norma brass.

Apologies Just trying to help.

 

[MeatBuck]

Meat
Sounds like you have it figured out. Use CBTO and I bet you see pretty consistent lengths from your die. I assume it’s a Redding die? Install the VLD seater stem and proceed to load to CBTO.

Yes Redding die and I’ll try the vld stem on these hammers if I’m not getting consistent cbto on the next batch. Otherwise I’ll save on it until I start on the Berger’s.
Panhandle precision does a little test of how the different stems contact the bullet differently just by coloring bullet with sharpie and twisting the bullet in the stem and checking marks. I’ll go with whatever is workin best for that particular bullet even if markings show better contact with one stem or the other.

 

[MeatBuck]

Apologies Just trying to help.

All good just making sure we stay on same page

 

[wind gypsy]

Your seating stem actually contacts the bullet forward of the ogive, or at least all of them I’ve measured. Some seating stems just don’t work well with certain types of bullets because of their shape. It’s not that they touch or bottom out at the bullet tip. The seating stem can actually bite into or grab the bullet on your upswing, moving it out. It’s not much and I’m not saying that’s what’s happening, but it can especially with light tension.

Can you see a ring or indent on your bullet between the ogive and the tip after they are seated? How many times have you fired this brass?

Very good point. So even though most in this thread indicate your die seats to consistent BTO lengths, in reality your die is only seating to consistent cartridge base-to-wherever-die-contacts-bullet lengths (let's call it BTWDCBL ). That is unless bullets are sticking in your die and being pulled out inconsistently.

Since most here agree it's preferable to use loading methods that result in more consistent BTO than COAL, you want a bullet/die combination that results in BTWDCB correlating closely with BTO rather than OAL. I've got a hunch doing this also correlates with less runout, tip damage, and deformed or sticking bullets.

This isn't something I'd previously given much thought...

 

[MeatBuck]

Here’s a good video that I watched and forgot about a few months ago when I was researching. Answers all my questions and most of yours in the first few minutes

 

[OXN939]

So even though most in this thread indicate your die seats to consistent BTO lengths, in reality your die is only seating to consistent cartridge base-to-wherever-die-contacts-bullet lengths (let's call it BTWDCBL)

Gonna be that guy. What this thread has been referring to as "ogive" is actually the very specific point at which the bullet first contacts the rifling, which is very close to where the shaft meets the ogive. To be technically correct, the ogive extends all the way from that point to the meplat, and comprises somewhere around half of the bullet's length.

So really, your seating die *is* contacting the bullet somewhere on the ogive, and as long as you leave that point to be consistent between rounds, BTWDCBL will equal CBTO to within a negligible degree of accuracy.

 

[Clucknmoan]

An ogive is an arc. So I guess if we need to we can start saying the apex of the ogive.

 

[MeatBuck]

And where your comparator measures may be a different point along the ogive than where your die touches. Making the measurements simply a reference point and not the exact point in which the bullet touches the lands. No cbto or coal or other is exactly the same as your chamber is, it’s simply a reference for repeatability. So long as the reference stays the same all data based on it will be repeatable.
Make sure your method of measuring the cbto stays consistent and there won’t be an issue.

Where the issues arise is with coal measurements.
And really these are only issues if you are either shooting a custom rifle, long range or loading outside of saami specs where precision matters most. If you stay in saami specs you would never care about cbto because you don’t get to change the amount of jump, it’s set by saami as coal and published for you to follow.
If you’re shooting a factory gun at ranges less that 300yds you will probably never see the inconsistencies in your ammo and really you are not making your ammo any better than factory.
Once you go custom or outside the saami spec then you actually get to play with jump and I think that’s where most of the confusion comes from. It’s guys who learned reloading by the saami book and not being open minded to an alternative method and also not crossing those methods up.
The only time a coal measurement makes any difference when your loading custom ammo is when your mag length limits how close you can get to the lands but that should be a secondary measurement taken only to ensure fitment but not used to set the length of the loaded round.

Im sure someone can poke a hole in this explanation but I think it’s pretty spot on.

 

[wind gypsy]

Gonna be that guy. What this thread has been referring to as "ogive" is actually the very specific point at which the bullet first contacts the rifling, which is very close to where the shaft meets the ogive. To be technically correct, the ogive extends all the way from that point to the meplat, and comprises somewhere around half of the bullet's length.

So really, your seating die *is* contacting the bullet somewhere on the ogive, and as long as you leave that point to be consistent between rounds, BTWDCBL will equal CBTO to within a negligible degree of accuracy.

View attachment 196017

An ogive is an arc. So I guess if we need to we can start saying the apex of the ogive.

Good clarifications. I use the terms for these measurements the same as Berger does as shown in the clip below.