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7mm Magnum Sizing

 
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  #1  
Old 06-02-2013, 01:35 PM
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7mm Magnum Sizing

Question, I have been reloading for seems like 100 years and have still failed to understand sizing on belted magnums. I can get away with may be 4 loadings before having to toss my brass. I've some folks using a nickel to set the sizing die, also there used to be a company that sold a die specifically for belted cartridges, and allowed you to size all the way to the belt. Would appreciate a bit of input on how you all set the die. Thanks, ElDee
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Old 06-02-2013, 04:27 PM
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Re: 7mm Magnum Sizing

I pay no attention to the belt . I resize it as though it is a regular bottle neck case . all I do is measure my fired brass and set my sizing die to bump the shoulder back about .002 . you will need a tool to measure case length . once fired brass will probably not be expanded completely , so I only neck size it the first time . after the second fire the brass should be fully expanded and you can set your die up to size the brass to your chamber .

so far I have not needed the belted case die .
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Old 06-03-2013, 12:57 PM
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Re: 7mm Magnum Sizing

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Originally Posted by jimbires View Post

after the second fire the brass should be fully expanded and you can set your die up to size the brass to your chamber .


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How do you do that with a full length seating die? Are you saying that you just don't adjust it down all the way to touch the top of the case holder with the ram all the way up?? If so, doesn't that mean that you're not resizing the whole neck?
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Old 06-03-2013, 02:48 PM
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Re: 7mm Magnum Sizing

Okay, so we see on the I T site that the proposal is to use standard FL sizing dies but adjust it to bump the shoulder by .002, and by using their headspace measurement tool to confirm your adjustment.

But isn't it the case (no pun intended) that if you do it that way with FL dies, you're not actually (outside) resizing the whole neck? If its okay to do that, they is there any reason to buy neck sizing dies?

Another question is, why bump the shoulder back .002? Is it to add some clearance to make cycling a round in more reliable?

I think having the ability to checking overall length when setting the die after changing bullet types or lengths by using the headspace guage. Bullet length is more variable than bullet ogive, unless there's a design change.
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Old 06-03-2013, 03:40 PM
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Re: 7mm Magnum Sizing

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Originally Posted by Shootin4fun View Post
How do you do that with a full length seating die? Are you saying that you just don't adjust it down all the way to touch the top of the case holder with the ram all the way up?? If so, doesn't that mean that you're not resizing the whole neck?

yes you are correct , your die will not touch the shell holder . your die should be sizing all of the neck . the die will size the neck until it touches the shoulder , then it will continue to size the neck while it pushes the shoulder back 0.002 .



Quote:
Originally Posted by Shootin4fun View Post
Okay, so we see on the I T site that the proposal is to use standard FL sizing dies but adjust it to bump the shoulder by .002, and by using their headspace measurement tool to confirm your adjustment.

But isn't it the case (no pun intended) that if you do it that way with FL dies, you're not actually (outside) resizing the whole neck? If its okay to do that, they is there any reason to buy neck sizing dies?

Another question is, why bump the shoulder back .002? Is it to add some clearance to make cycling a round in more reliable?

I think having the ability to checking overall length when setting the die after changing bullet types or lengths by using the headspace guage. Bullet length is more variable than bullet ogive, unless there's a design change.

yes you should be resizing the whole neck , with the die adjusted this way . some guys still neck size only , I don't . I do have a few Lee collet dies , these only neck size , but then I also use a body die to push the shoulder back 0.002 . which is basically doing the same thing as using a full length die .

bumping the shoulder back will ease cambering your ammo . if you neck size only , after a couple reloads the bolt will be hard to close on your rifle .

yes I measure my COAL from the ogive . it is much more accurate than off the tip .

redding makes the competition shellholder set , these are nice . I use these with a RCBS precision mic . it makes setting up your die easy . Jim

Competition Shellholder Sets | Redding Reloading Equipment: reloading equipment for rifles, handguns, pistols, revolvers and SAECO bullet casting equipment
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  #6  
Old 06-03-2013, 03:51 PM
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Re: 7mm Magnum Sizing

When belted mag's were the norm for long range shoulder fired prone matches, the best scores were shot with new cases or fired ones full length sized all the way to the belt and setting the shoulder back a couple thousandths. Folks used to cut the body part out of a standard FL die then square its bottom to size the ridge in front of the belt back down all the way to the belt so it didn't interfere with the case shoulder slamming cleanly into the chamber shoulder perfectly centering the round when it fired. Such a die's called a "body" die for belted cases.

Belted cases sized to headspace on their shoulders will center the case neck and therefore the bullet best in the chamber anyway. The firing pin drives the case forward hard into the chamber shoulder and that's what best centers the front of the case in the chamber.

Larry Willis now has a collet die that's a lot better than a "body" die. Cases so full length sized can get 15 to 20 reloads with max charges easily.

That aside, unless your and your hardware can shoot belted cases no worse than 1 MOA past 500 yards, that collet die may not make a difference. Just use a standard FL die and don't set fired case shoulders back too far. Seat bullets so they gently seat back a bit as they crunch into the rifling; that well centers even the crooked ones.
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Old 06-04-2013, 08:42 AM
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Re: 7mm Magnum Sizing

Quote:
Originally Posted by jimbires View Post




yes you should be resizing the whole neck , with the die adjusted this way . some guys still neck size only , I don't . I do have a few Lee collet dies , these only neck size , but then I also use a body die to push the shoulder back 0.002 . which is basically doing the same thing as using a full length die .

This my method as well. I use this same process for all my rifle cartridges. I've never paid the belt any mind, it's one of those things that seemed like a good idea at the time but turned out to be more of a fruit blister than anything useful.
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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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