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ogive confusion...

 
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  #8  
Old 02-26-2013, 06:19 PM
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Re: ogive confusion...

Quote:
Originally Posted by Joe King View Post
I think I'm reading the question a bit different.

Your thinking that if the ojive is consistent that the cartridge OAL should stay the same as long as every bullet is seated the same distance from contacting the lands (assuming the bullets are of same manf and style i.e. 7mm 162 Amax )? While that would be ideal that isn't how it happens. The area of the Ojive that you want to worry about is the area where your comparator and your seating plug, and your rifling contact the bullet. Forward to the tip of the bullet from that point doesn't matter beyond the down range effect the minor change in BC will have. And it's dman near impossible for bullet manufactures to control the very forward end of the bullet Ojive and tip. You can however, if you trim the tip and point the bullet, but if your hunting with these bullets I would not do that as it can (and probably will) change everything about terminal performance

As others have stated, you'll be better off worrying about the bearing surface length, one intersting thing I have noticed with quality bullets like Berger, or customs, and mass manf to a lesser degree. Is that if you sort them out to say about 0.002" in bearing length they'll be really really consistent in weight too.
Ok. I may be a little over my head now. Here is my problem. I load a 175gr SMK at 2.80 COAL. I adjust my die usually on the first bullet to get this legnth. From what I understand, you don't want to keep adjusting your seating die up and down to reach a 2.80 COAL once loading rounds bc your ogive will vary. Keeping the seating die the same will produce bullets with the same ogive OAL. This is assuming of course that each bullet ogive is the same.
When I do this I will get very different COAL on many rounds. I assume it's bc the differences between the ogive and tip of many bullets. That's fine.

I ordered the bullet comparator to ease my mind and measure each bullet ogive prior to seating them so I know they will rest in the rifling the same. If the COAL is different then so be it. But right now I have no idea. I just know that some will measure 2.80 and others 2.72. That bugs me.

My thought process correct?
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Old 02-26-2013, 08:09 PM
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Re: ogive confusion...

I was wondering about this once so I did some checking on the ID of the comparators and the approx ID of the seating stem where it would hit the bullets. All of my comparators are .011" below caliber

Here is a 308 caliber comparator and it is .297" tight on the pin



Now seating stems probably vary quite a bit, but we all have observed that they seem to hit the bullet about halfway toward the tip. I only checked one since all my seaters are locked in and I don't want to take them apart, but the 308 seater die hits the bullet at approx .260"



so to me it would be more accurate to gauge your bullets as you seat them with the comparator and adjust your seating as you go along than to set your seater at one place and leave it there. Not to be anal about getting each bullet down to the .001" OAL but because during a string of bullet seating, connections on the press and dies can change slightly.

YMMV
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  #10  
Old 02-26-2013, 08:14 PM
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Re: ogive confusion...

I apologize for not reading the entire thread but will ad this and hope it has not been suggested.

If you want more consistent seating depth , head to o-give, set the seating die up to slightly cam over against the shell holder at the top of the stroke. This will lessen the effect of how hard you stroke the handle in relation to the depth it seats the bullet.

Jeff
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Old 02-26-2013, 10:16 PM
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Re: ogive confusion...

Idealy then using a seater stem that is .300 for a .308 would be ideal. If your comparator is actually .300. this would be the only way to sort bullets and seat them identically ??? Or did I analize this wrong?
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  #12  
Old 02-27-2013, 09:07 AM
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Re: ogive confusion...

Hmmmm too much analyzing going I think. After getting the comparator, set the seating die to seat the bullet the correct distance off the lands by measuring the base of the case to the ogive of the bullet. Once that is done, you are done until you change bullet brands or possibly even lots.

For example I have 2 boxes of 100 bullets from the same lot that I will not change my seating die depth on until I change lots or different bullet. I simply measured the bullet ogive to case base using my Hornady OAL guage, subtracted .075, and it gives me a number such as 2.585 - .075 = 2.510 set the die to seat the bullet to 2.510.....done.
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  #13  
Old 02-27-2013, 11:13 AM
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Re: ogive confusion...

Quote:
Originally Posted by Texas Republic View Post
Ok. I may be a little over my head now. Here is my problem. I load a 175gr SMK at 2.80 COAL. I adjust my die usually on the first bullet to get this legnth. From what I understand, you don't want to keep adjusting your seating die up and down to reach a 2.80 COAL once loading rounds bc your ogive will vary. Keeping the seating die the same will produce bullets with the same ogive OAL. This is assuming of course that each bullet ogive is the same.
When I do this I will get very different COAL on many rounds. I assume it's bc the differences between the ogive and tip of many bullets. That's fine.

I ordered the bullet comparator to ease my mind and measure each bullet ogive prior to seating them so I know they will rest in the rifling the same. If the COAL is different then so be it. But right now I have no idea. I just know that some will measure 2.80 and others 2.72. That bugs me.

My thought process correct?
yes that is what I was saying, the only other option I can see is to get an adjustable reamer and ream out your comparator and seater plug to have the exact same inside dia as your lands. Hell I might do that now that I think of it.
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Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.

Joe
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  #14  
Old 02-27-2013, 11:27 AM
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Re: ogive confusion...

Quote:
Originally Posted by woods View Post
I was wondering about this once so I did some checking on the ID of the comparators and the approx ID of the seating stem where it would hit the bullets. All of my comparators are .011" below caliber

Here is a 308 caliber comparator and it is .297" tight on the pin



Now seating stems probably vary quite a bit, but we all have observed that they seem to hit the bullet about halfway toward the tip. I only checked one since all my seaters are locked in and I don't want to take them apart, but the 308 seater die hits the bullet at approx .260"



so to me it would be more accurate to gauge your bullets as you seat them with the comparator and adjust your seating as you go along than to set your seater at one place and leave it there. Not to be anal about getting each bullet down to the .001" OAL but because during a string of bullet seating, connections on the press and dies can change slightly.

YMMV
I wonder if you went up 1 or 2 cal on your seating stem if they would contact the ojive closer to the comaritor and where the lands contact without contacting the meplat. Something to think about.
__________________
Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.

Joe
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