Bullet seating depth question.

ravot22

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Dec 16, 2013
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My CBTO to can change as much as .003 on finished products.

I know bullets can be slightly different in overall length and ogive.

Should I set the bullet seater and forget about the difference in CBTO? Or

Would it be better to "walk" the bullet to the proper seating depth?

For example, If I'm looking for a CBTO of 2.750, set the bullet at 2.760 and then use the micro adjustments on the bullet seater to fine tune the seating depth to 2.750?

Thanks in advance for all your help!
 

Canadian Bushman

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Jan 24, 2012
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Houston, Texas
My CBTO to can change as much as .003 on finished products.

I know bullets can be slightly different in overall length and ogive.

Should I set the bullet seater and forget about the difference in CBTO? Or

Would it be better to "walk" the bullet to the proper seating depth?

For example, If I'm looking for a CBTO of 2.750, set the bullet at 2.760 and then use the micro adjustments on the bullet seater to fine tune the seating depth to 2.750?

Thanks in advance for all your help!


I set up the bullet seater, then verify it with a full press. In other words a press of the distance i would normally seat a bullet at, unlike the small steps i would use to creep up on my nominal measurement. Then i leave it alone and verify its within a couple thousandths every few rounds.

This usually gets me within +\-.001
 

ShtrRdy

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High Plains
You might try measuring the bullets base to ogive. This might be where the variation is occurring. If this is the case then load at a constant setting on the seating die so that the base of the bullet is in the case the same amount.
 

TK50

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Dec 15, 2008
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You didn't say how you were measuring the lengths of your loaded rounds on your post. If you are measuring them from the base of the case to the tip you will get uneven numbers. You will need to use a stoney point tool or something similar to get more accurate seating depth measurements. You should also sort your bullets for ogive length if you want them to be as close as possible in seating length measurement. Depending on how much neck tension you are using on your loaded rounds you would do more harm than good in trying to sneak up on your target depth. If you try to do that you will see more variance than what you are now dealing with.
 

ravot22

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Dec 16, 2013
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You didn't say how you were measuring the lengths of your loaded rounds on your post. If you are measuring them from the base of the case to the tip you will get uneven numbers. You will need to use a stoney point tool or something similar to get more accurate seating depth measurements. You should also sort your bullets for ogive length if you want them to be as close as possible in seating length measurement. Depending on how much neck tension you are using on your loaded rounds you would do more harm than good in trying to sneak up on your target depth. If you try to do that you will see more variance than what you are now dealing with.

I use a Hornady comparator to measure the finished bullets.

Thanks for everyone's advice. I see a couple areas of improvement I need to explore.
 

4xforfun

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Take a step back and think about this for a moment. Lets say that you have some bullets that vary in length, bearing serface, whatever. Your bullet seating die is what it is. It seats bullets based off of the size of the bullet at the contact point of the seater. Different seaters contact the bullets in different places. Lets say you are loading 168 grain SMK's, and some are longer than others. The cartridge OAL or base to ojive length will be the same weather the bullets is long or short. It is just that the longer bullet will be stuffed into the case deeper and visa versa for shorter bullets. And if the ojive of the bullets differ within a lot of bullets, what can you do. Adjust your die for each and every bullet? Or, soft seat your bullets so that the bullet seats itself when you close the bolt? OK idea in comp...hunting..not so much!!

The measurements that can make a difference is the bearing serface length. The only thing you can do about that is to sort your bullets into groups with the same measurements and shoot them together.

And, ALL of this, in my opinion, doesn't have much relavence in hunting situations. I am not even sure that all of the sorting I did made much of a difference in 1000 yard BR. I did it all, and I won lots of wood, but I also did a dozen other things....little, nitpicky things.

I always said.." I take 7 precise steps to prep my brass for competition, only 4 of which actually help. The problem....I don't know which 4 that is!!"

Don't know if any of this makes sense, as my grasp of the English Language is limited. I guess it works out in my head!! :rolleyes:

Tod
 

TK50

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Dec 15, 2008
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Tod is right with many of the points he brought up in his post. I am a 1000Yard BR competitor also. It all depends on how much prep work you want to get into with your loads. Are you planning to shoot competitively with them or are you looking to load the best hunting ammo you can? The most accurate way to sort bullets is to sort them by ogive to pressure ring length which is like Tod said essentially bearing surface. There are not many tools that measure bullets that way most measure from base to ogive length. One other thing you didn't mention was the state of your brass. Is the brass fired many times or is it just fire formed? Have you been annealing your brass? Brass that has been fired a number of times can have varying degrees of neck tension which will lead to spring back on the bullets and can also give you the problems you are having.
 

FearNoWind

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Jul 10, 2012
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North Central Valley California
...The only thing you can do about that is to sort your bullets into groups with the same measurements and shoot them together. ...
ALL of this, in my opinion, doesn't have much relevance in hunting situations....
I always said. ." I take 7 precise steps to prep my brass for competition, only 4 of which actually help. The problem....I don't know which 4 that is!!"
Don't know if any of this makes sense, as my grasp of the English Language is limited. I guess it works out in my head!! :rolleyes:

Tod

As well as you explained that, Tod, I don't see anything limited in your grasp of English. Well said ..... :)
Love the seven step comment. :cool:
 
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