Help with .308 OAL Case Lenght

Kouma - forget about case length and trimming having anything to do with cartridge length. You are never going to seat a bullet so deep that your seating stem will ever contact the case and if you do, you're having bigger problems than we can rectify here.

To repeat, when seating a bullet, only the front of the bullet and the bottom of the case will be touching the working bits of the seating die. The case length is irrelevant.
 
I purchased a co-ax press, Forster competition dies, Wilson trimmer, and hornady comparator. I know I went overboard. Anyways, I finally got around to makes my first bullets. I measured from the ogive and still my numbers are not consistent. I noticed that even with a comparator, depending on how you measure using the calliper the results are different. I am very frustrated now or maybe just obsessed. Not sure what else to do and why my results are still not consistent.

All I want is consistency in my cases OAL. Is this too much to ask?
 
Modern loading charts show a COAL for the cartridge you are using.
All this figure means is if you are using a rifle which has specifications in agreement with the SSAMI guide lines, the cartridge will fit in your rifle. The figure means nothing more, nothing less.
In other words the figure is a nothing. It means the cartridge should be seated deep enough, should work through the magazine and when it is chambered, the bolt should close.
Couldn't you figure this out by yourself, your cartridges in your rifle? If they fit, shoot them.
 
kouma said:
I purchased a co-ax press, Forster competition dies, Wilson trimmer, and hornady comparator. I know I went overboard. Anyways, I finally got around to makes my first bullets. I measured from the ogive and still my numbers are not consistent. I noticed that even with a comparator, depending on how you measure using the calliper the results are different. I am very frustrated now or maybe just obsessed. Not sure what else to do and why my results are still not consistent.

All I want is consistency in my cases OAL. Is this too much to ask?
Click to expand...

Keep in mind OAL should be fairly consistent off the ogive, not perfect. From your description i think it might be your technique that needs more practice. Using a caliper and comparator is easy. Using them precisely takes practice. You said these were your first bullets. If you are careful your second and third will be better.

For example, can you measure 3 rounds over and over again in a random blind order and get the same measurements each time? This is an easy technique to see where the problem might lie.

Also the wilson trimmer is excellent and the only one Ill use.
 
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H4831 said:
Modern loading charts show a COAL for the cartridge you are using.
All this figure means is if you are using a rifle which has specifications in agreement with the SSAMI guide lines, the cartridge will fit in your rifle. The figure means nothing more, nothing less.
In other words the figure is a nothing. It means the cartridge should be seated deep enough, should work through the magazine and when it is chambered, the bolt should close.
Couldn't you figure this out by yourself, your cartridges in your rifle? If they fit, shoot them.
Click to expand...

It is not that they don't fit, they do. I am trying to create my most accurate ammo and I dont see that without ensure every round is 100% consistent.
 
curseyou said:
Keep in mind OAL should be fairly consistent off the ogive, not perfect. From your description i think it might be your technique that needs more practice. Using a caliper and comparator is easy. Using them precisely takes practice. You said these were your first bullets. If you are careful your second and third will be better.

For example, can you measure 3 rounds over and over again in a random blind order and get the same measurements each time? This is an easy technique to see where the problem might lie.

Also the wilson trimmer is excellent and the only one Ill use.
Click to expand...



I did notice, depending on how you erect the bullet in the comparator, the caliper give different results. Is this normal or am I doing something wrong here.
 
The only other thing that I noticed that could affect oal consistency is neck tension, having to much or to little. Other thing that comes to mind is powder volume if the case is packed with powder (compressed load) some times the powder pushes back against the bullet changing the OAL constancy. Ultrasonic cleaned brass it's also more grippy on the inside of the neck, I've notice this has a little bit of influence on seating consistency (feel). Just my 2 cents.
 
OK - Before you develop a complete case of OCD. Take a reference bullet and an empty case. Seat it to your desired COAL. Measure with your gear both at the ogive and bullet tip. Repeat process with the same bullet five times. Report back to us.
 
cosmic said:
OK - Before you develop a complete case of OCD. Take a reference bullet and an empty case. Seat it to your desired COAL. Measure with your gear both at the ogive and bullet tip. Repeat process with the same bullet five times. Report back to us.
Click to expand...

Here are the five measurements of one round that I recently reloaded (tip/ogive):

1- 2.8175 / 2.2280
2- 2.8175 / 2.2270
3- 2.8175 / 2.2240
4- 2.8175 / 2.2280
5- 2.8175 / 2.2235

This is the issue with measuring the ogive, depending on how your erect the bullet (the angel) it could affect the measurement..
 
According to Hornady "Measuring cartridge lengths across bullet tips is not a reliable or repeatable method for measuring your loaded rounds. It's common for variations of up to .025" to exist from one round to the next. Our Bullet Comparator solves that problem by measuring rounds from a reliable surface on the bullet, the ogive, to provide consistent, precise measurements of your rounds." It definitely doesn't seem to be the case in my experience.
 
308BAR said:
The only other thing that I noticed that could affect oal consistency is neck tension, having to much or to little. Other thing that comes to mind is powder volume if the case is packed with powder (compressed load) some times the powder pushes back against the bullet changing the OAL constancy. Ultrasonic cleaned brass it's also more grippy on the inside of the neck, I've notice this has a little bit of influence on seating consistency (feel). Just my 2 cents.
Click to expand...


I dont get how the neck thickness has anything to do with the OAL of the cartridge. Shouldn't the force from the press be sufficient to seat the bullet through the neck regardless if how tight the neck is. Same thing with the powder.
 
Not sure you got the gist of my post. Did you pull the reference bullet and reseat it before re-measuring? Anyway, you've proved to yourself that the comparator has some inherent inaccuracy...
FWIW - I don't get too hung up on the absolute value of the COAL. I keep the same reference bullet (marked with black marker), and use it every time I make a new batch of that bullet weight and make. By setting the seating die with the same bullet, I get repeatability. I don't have or need a comparator. My COAL's do vary +/- 10 thou, due to the fact that I'm using lead tip bullets and the tip geometry varies from bullet to bullet. (Easily proved by direct measurement)
I do record the actual length of the reference bullet. If I manage to lose it, I can pick out another bullet to serve as the reference bullet.
 
Take a look at a few bullet tips. Even the Hdy match that I use have variations in the tip of the bullet (angle, sometimes there will be a high side or other things). For fun, measure a few bullets and see how much variance you get. For me, I tend to make to whatever coal I want for the first in the batch, then stop measuring other than 1 or 2 to check nothing has drifted out of whack. The press and dies are pretty precise, it's the bullets that are the culprit most of the time.
 
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