To bush or mandrel

[Lonewolf74]

Mikecr, looking to make sure I understand your sizing method.

So say it's a 338 caliber cartridge, loaded neck size is .365. You would choose a bushing .002 under .365 which is .363. You would then size only the length of the neck in which your bullet's bearing surface is in contact with. Then the final step is to expand with a mandrel at bullet diameter which would be .338.

Do I have this all correct? If this is correct how do you measure exactly the length of the neck that needs to be sized?
Sometimes I get hung up on the small details!

 

[338 dude]

Mikecr, looking to make sure I understand your sizing method.

So say it's a 338 caliber cartridge, loaded neck size is .365. You would choose a bushing .002 under .365 which is .353. You would then size only the length of the neck in which your bullet's bearing surface is in contact with. Then the final step is to expand with a mandrel at bullet diameter which would be .338.

Do I have this all correct? If this is correct how do you measure exactly the length of the neck that needs to be sized?
Sometimes I get hung up on the small details!

.363

 

[Lonewolf74]

.363

Whoops yea I meant .363 not .353

 

[Mike Matteson]

It's my understanding that annealing the brass each time allows it to expands the same every time if done correctly. Each time you fire your round it works the brass and changes the hardness, even when reloading the case works the brass. So I will stand by annealing each time. I didn't before, but looking into it more, I have changed how I do things now. I know for sure that annealing my cases extended the life of the brass greatly. No more split necks.

 

[Tiny Tim]

I don't necessarily disagree, but I believe Mike Cr's point was also that he is not running a SAAMI spec chamber that allows the neck to expand excessively during firing either.

 

[L.Sherm]

Mandrel expanding will give 0.001" or less runout.

So will expander buttons if all your S hit is right.

 

[Tech4]

That process annealing to manage tension is needed less often.
With reasonable neck clearance (<3thou) you can probably go many cycles without re-annealing. Possibly more than your cases will last anyway.

I anneal initially for fire forming, and then later as needed. I know it's time when I'm fighting to match measured seating forces.
If your annealing is really good (like salt bath good), and chambers are big in clearances, then you might anneal more often than I do.
Makes sense.

How are you measuring seating forces?

 

[fightthenoise]

How are you measuring seating forces?

Arbor press with a force gauge most likely

K&M Precision Arbor Press with Standard Force Measurement Ra

 

[wonderman4]

So will expander buttons if all your S hit is right.

I agree, but with mandrels, all your S hit does not have to be nearly as right.

 

[L.Sherm]

That may be true to some extent, I dont want some people to believe you can't get straight brass from expander balls.
Run a size neck through a mandrel thats .003-.004 out it won't straighten it out to .001. How many check runout on the outside of necks and how many check it on the inside on your unturned brass.

 

[Mikecr]

So say it's a 338 caliber cartridge, loaded neck size is .365. You would choose a bushing .002 under .365 which is .363. You would then size only the length of the neck in which your bullet's bearing surface is in contact with. Then the final step is to expand with a mandrel at bullet diameter which would be .338.

Do I have this all correct? If this is correct how do you measure exactly the length of the neck that needs to be sized?
Sometimes I get hung up on the small details!

I use a bushing that provides 2thou interference after spring back.
The bushing that does this depends on the bullet diameter and neck thickness and fired neck OD and hardness.

I measure pre-seating forces, so that I can match this before seating actual bullets.
I do this with a mandrel die fitted with a loadcell, and neck sizing LENGTH adjustments.

 

[Mike Matteson]

Whoops yea I meant .363 not .353

Correct me if I am wrong. I am figuring that you are using .0135 neck wall thickness to come up .365 O.D. Which is fine, and that about what I cut my neck thickness too. Depending on the spring back would determine the mandrel size, "Correct". That maybe more or less depending on the brass. That where I come back at annealing every time. You are working the brass while sizing and firing the round or brass which it make is less pliable and harder each time the case is fired. So the neck tension would increases even with only the down sizing of .002 under each time, because of the metal getting harder and less pliable. Or that's the way I see it. Correct me if I am wrong. The release of the bullet from the case would be the same tension by the way you are explaining it, because you would be using the same brass as a group. I agree mostly with what you are stating, and I have a better understanding on how to look at it too.

 

[Lonewolf74]

I'm still trying to grasp some of this myself and am unable to clarify for you. I haven't gone down the road of experimenting with different neck tension and interference but do believe it's the next step to a higher level.

My numbers are based off a cartridge I'm currently playing with so it's fresh in my mind and also based off perfect conditions where you get .001 spring back with each sizing step. I believe experimentation would be needed to achieve real results based on spring back. I could also see where spring back could be greater in one direction then the other. It would make sense to me that the neck would have a tendency to spring back more (outward) after sizing down the neck diameter then it would to spring back (inward) after expanding. Of course this could be a nearly immeasurable difference or wrong all together.

It does make sense to me in what Mikecr states that anything more then the spring back of the brass is going to yield to the bullet during seating, just as if it was expanded by a mandrel. Unless the brass neck is strong enough to size (squeeze) the bullet which I doubt and don't think would be desirable

 

[Mike Matteson]

It better or there a problem. The part of the neck tension is being constant, and then figuring out what your rifle likes. That I believe what Mikecr is driving at. I feel he will correct me if I am wrong. That fine by me. I feel he has enlighten me, or given me a better understanding, which I am grateful for. How I reloaded before and what I am working on is almost two different things.