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Polishing a body die?

 
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  #29  
Old 08-15-2013, 09:11 AM
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Re: Polishing a body die?

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Originally Posted by larrywillis View Post
As I said in post 17, it would take a very long chapter to fully explain shoulder setback. There are a jillion different calibers, hard primers, soft primers, light/fast firing pins, heavy/slow firing pins, that affect shoulder setback.
I know all that.

But I don't think you quite understand that any bottleneck case headspacing on its shoulder has its shoulder hard against the chamber shoulder when the round fires. And it's held there while the case expands pushing the back part of the case against the breech face. Proof's seen by powder residue typically showing up on case necks, but not on the case shoulder.

Therefore, such shoulders are not blown forward as you say. And I explained why in one or two sentences.

But I used to think that way years ago until a 'smith showed and told me how to find out for sure.
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  #30  
Old 08-15-2013, 09:32 AM
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Re: Polishing a body die?

Bart B ......

When you see that 99.9% of all case head separations are at the rear of the case . . . . . it's obvious.

The amount of shoulder setback is the big variable.

Getting technical information (like this) from the Internet is sometimes like trying to take a drink of water at the base of Niagara Falls . . . . . there's a whole lot coming, it never stops, and you might not get exactly what you're after.

I don't recommend polishing the die in this situation.
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  #31  
Old 08-15-2013, 10:48 AM
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Re: Polishing a body die?

Quote:
Originally Posted by larrywillis;838549When you see that 99[B
.[/B]9% of all case head separations are at the rear of the case . . . . . it's obvious.
That's not the reason.

It's partially the thinner case body wall at the shoulder and thicker case wall at the head that causes it as the front part of the case is pushed hard against the chamber wall long before the back part is. It's the back part that does most of the stretching.

The other part is the pressure ring area is where maximum work hardening of the case is at from enlarging when fired to reducing when sized down. The head and back 1/8th inch of the case changes diameters very little. It starts 2/10ths inch in front of it is. That weakens the case body at that point.

Rarely, if ever is there such a thing as "shoulder" separation. The case head breaks off from all the elasticity being removed from the brass at the pressure ring.
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  #32  
Old 08-17-2013, 03:37 AM
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Re: Polishing a body die?

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Originally Posted by Bart B View Post
That's not the reason.

It's partially the thinner case body wall at the shoulder and thicker case wall at the head that causes it as the front part of the case is pushed hard against the chamber wall long before the back part is. It's the back part that does most of the stretching.

The other part is the pressure ring area is where maximum work hardening of the case is at from enlarging when fired to reducing when sized down. The head and back 1/8th inch of the case changes diameters very little. It starts 2/10ths inch in front of it is. That weakens the case body at that point.

Rarely, if ever is there such a thing as "shoulder" separation. The case head breaks off from all the elasticity being removed from the brass at the pressure ring.
Bart is correct on this . Polishing a die is no big deal if you start with something that is too tight to start with and don't go any further than you need to size the case to fit with some chambering clearance. Head space will not be affected if you cut the shoulder section away from the lapp before you start . That way you only lapp the body diameter out .
I have lapped a few dies and had no problems it's not rocket science .
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  #33  
Old 08-17-2013, 07:37 AM
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Re: Polishing a body die?

Bullet Bumber .......

You're right, this is definitely not rocket science. However, as a die manufacturer, and after taking jillions of phone calls from shooters (every day for the last 12 years), I can tell you that most shooters should be more interested in adjusting their die height accurately.
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  #34  
Old 08-17-2013, 07:58 AM
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Re: Polishing a body die?

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Originally Posted by larrywillis View Post
...I can tell you that most shooters should be more interested in adjusting their die height accurately.
Very well put.

I'm convinced that most reloaders do not know how to accurately adjust their sizing dies. Especially when the common way is to "twist the die 1/4th turn" between sizing tests.

How many reloaders know that a 1/4 turn on a die moves it about .018"?

How many can figure out why?

When I say "most" that means the smallest fraction over half of them makes it a true statement. 501 reloaders out of 1000, for example.
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  #35  
Old 08-17-2013, 08:56 AM
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Re: Polishing a body die?

Well, tell me if I am doing it correctly then. I start with the die not contacting the shell holder when the ram is all the way up. I make very small turns on the die and check the headspace on my gauge and chamber the brass in my rifle after each turn. Since i go so slow and I've done it so many times, I can fell when I get a .001 bump just by how the brass feels when chambered in the rifle. However I always check with the gauge first. I have found that setting the die up to the manufacturers recs can result in as much as a .015 bump. I also put a magic marker mark on the datum line so I can visually see when it's touched.
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