A question for those who sort their bullets.

[Nowhere Man]

After you've measured base to ogive and sorted your bullets into piles, do you readjust your seating die for each pile to maintain the same distance from ogive to lands?

 

[mmcu]

Yes.

 

[hrlincoln]

No. The seating stem, once adjusted for desired CBTO, should position the bullet at the same point with respect to the lands regardless of different bullet base-to-ogive measurements. What will be different, however, is where the base of the bullet is in the neck due to the differing bullet measurements.

 

[KenOath]

IME above is correct, your jump or jam will remain the same but the amount of bearing surface of the bullet in the neck will be more or less depending on bto lengths..

 

[Nowhere Man]

I knew I was trying to overthink it. Thanks.....

 

[JFrank]

Above is correct, your jump or jam will remain the same but the amount of bearing surface of the bullet in the neck will be more or less depending on bto lengths..

Gents
If I may chime in '
I'm hearing trust the seater even though the CBTO is varying from bullet to bullet and don't adjust ?
J

 

[KenOath]

CBTO shouldn’t vary much even if your projectiles are shorter or longer BTO

 

[JFrank]

CBTO shouldn’t vary much even if your projectiles are shorter or longer BTO

I've encountered BBTO the same however CBTO varying as they come out of the seater, understanding that the seater will contact in a different location than the comparator which shall I trust is the question of my week?
My target says something is wrong
J
CBTO varying.008

 

[mikeeg02]

I think the OP is talking about specifically sorting bullets. Not loaded rounds. I think.

If you've sorted bullets into piles and well call BBTO as done above, seat them into the cases as you normally would. Now measure CBTO. You can sort them into piles, and then adjust your seater to make CBTO consistent. It can be hard to find your rythem to get consistent CBTO with a standard press. But it is important.

Using an arbor press with hand dies really makes life a lot easier in this department. Some people figure out a method using standard dies and press to be consistent. That's how I did it before getting hand dies, and a great shooter friend of mine still does it. Seats them all .002" short. Groups them in piles, and adjust the seater accordingly for a second seating. So as to not have them go in too deep.

I'm not sure what discipline you're shooting or loading for. We do our best to be competitive lol

 

[KenOath]

I've encountered BBTO the same however CBTO varying as they come out of the seater, understanding that the seater will contact in a different location than the comparator which shall I trust is the question of my week?
My target says something is wrong
J
CBTO varying.008

Donuts can cause seating depth to vary if one donut is taller than the other, that’s if the bearing surface is making contact with the donut .. .008” is considerable..

 

[JFrank]

Donuts can cause seating depth to vary if one donut is taller than the other.. .008” is considerable..

Indeed
I'm loading the same lot number 107SMK for my br as Dusty pointed out Sierra lot numbers don't mean much.
Perhaps just a bad batch
Normally I measure and sort everything once set the seater and go , checking periodically they remain consistent however this batch is puzzling
J

 

[mikeeg02]

CBTO varying.008

That much variance can be in how you use your press. When I was trying to figure that out, I spoke with Redding as I had a comp seater. They suggested seating as usual but letting the last 1" of travel at the ball on the end you push with your hand to free fall. That helped me significantly when I still used regular dies.

They said the reason for that is the assembly is cast. And when you push it to the stop, depending on speed and force applied you actually bend it some.

 

[JFrank]

I use a RCBS RS press with a Forster micro seater all has been consistent until this batch of SMK perhaps just move to the next box
J

 

[mikeeg02]

You may also consider taking it apart and cleaning the stem and body. As round count goes up, so does the dirt/grime. May not be the bullets at all, though it could be.

 

[Bart B.]

After you've measured base to ogive and sorted your bullets into piles, do you readjust your seating die for each pile to maintain the same distance from ogive to lands?

I don't think that's necessary. If there's. 010" spread in BBTO, seating all of them with the same setting will only make the bullets base a .010" spread inside the case neck from where the seater stem seated them. The CBTO will be the same across all.

I went through a dozen or more tools and procedures to keep bullets' jump distance to the rifling consistent. Three things learned....

* For bottleneck cartridges headspacing on their shoulders, the case shoulder is against the chamber shoulder when the round fires.

* When the round fires, case heads are off the bolt face at least as much as the difference between chamber headspace and that of the case. Case rims are thinner than minimum extractor claw to bolt face dimension by several thousandths.

* Critical place on bullet to measure from is where it first touches the rifling. It ain't the bullet's tip and not any diameter smaller than barrel bore diameter.

Therefore, the distance from case shoulder to rifling contact diameter in the bullet is what matters. It's about .002" to .004" less than bullet diameter depending on diameters and angles at touch point and never smaller than the barrel's bore diameter. The case head is typically a bit off the bolt face.

Does any seater stem contact bullets at any diameter larger than bore?

The rifling erodes down the barrel .001" every one to several dozen shots fired. To keep bullet jump distance consistent, you gotta seat bullets less.

All the bullets in a given lot will not have all ogive shapes match exactly the pointing dies ogive. And nobody makes the milling reamer's ogive to make each pointing die's ogive exactly the same. There are tolerances.

I'm not aware of any rifle whose chambered case's heads are all held against (touching) the bolt face as the round fires.

 

[TimS]

Their

 

[Bart B.]

The seating stem should position the 'ogive' (or point where stem contacts bullet's surface) at the same point with respect to the lands

Good idea, but are there any stems whose bullet contact point diameter is no diameter smaller than the barrel bore diameter to do that?

 

[hrlincoln]

Good idea, but are there any stems whose bullet contact point diameter is no diameter smaller than the barrel bore diameter to do that?

Not sure I follow your question. Went back and edited my post...maybe my explanation wasn't clear.

 

[270WinDude]

I think the OP is talking about specifically sorting bullets. Not loaded rounds. I think.

If you've sorted bullets into piles and well call BBTO as done above, seat them into the cases as you normally would. Now measure CBTO. You can sort them into piles, and then adjust your seater to make CBTO consistent. It can be hard to find your rythem to get consistent CBTO with a standard press. But it is important.

Using an arbor press with hand dies really makes life a lot easier in this department. Some people figure out a method using standard dies and press to be consistent. That's how I did it before getting hand dies, and a great shooter friend of mine still does it. Seats them all .002" short. Groups them in piles, and adjust the seater accordingly for a second seating. So as to not have them go in too deep.

I'm not sure what discipline you're shooting or loading for. We do our best to be competitive lol

I think I am heading towards the same direction as your friend. be it bullet variance or equipment issues.

Also, if I'm going to wrap my head around this issue, which I really want to have an opinion on, I'm first going to need to know what BBTO and CBTO stand for lol

 

[#40Fan]

Bullet base to ogive. Cartridge base to ogive.

@South Prairie jim, make sure the seating stem is cut far enough that it isn't making contact with the meplat of the bullet.