Shoulder Bumping


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Matt304
February 20, 2011, 02:52 PM
Case shoulders can be made longer by the process of fire-forming them in a longer chamber.

What can one do if a case shoulder is needed to be made shorter?

I am shortening the neck of a case by trimming it 0.130". After I trim the neck down, I would like to gain some of the neck that was lost by pushing the shoulder down and increasing the shoulder angle. I would like to move the neck/shoulder junction of the case down by roughly 0.060".

This is being done to meet a certain OAL length requirement of a new cartridge I am developing.

Does anyone have experience with working brass down like this in a die? I have bumped case necks down by smaller amounts myself with a bushing die, but I am unsure if what I want to do (changing the shoulder angle) is possible without improperly deforming the case while running it into a die.

Thanks

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k4swb
February 20, 2011, 03:39 PM
I hope I can explain this.
I shoot a wildcat called a .222 Haney. It is sort of a .222 Rem improved with a 37^ shoulder and short tight neck.
I like to actually use .223 brass for this so I have to trim the necks way back, lube the shoulder neck area and run the shortened .223 cases through a .222 rem full length die just enough to bump the shoulder back to get the case to fit in the .222 Haney chamber. I don't recall just how much it is pushed back but it is no real trouble to do. Once in awhile a case just doesn't want to be bumped back and it will buckle but not too often.

I don't know if this helps at all but it sounds about like what you're doing.

Walkalong
February 20, 2011, 05:46 PM
I would like to move the neck/shoulder junction of the case down by roughly 0.060".
If you are doing it to fit a custom chamber, fine, but if not, you are asking for a case head separation when you fire it.

Matt304
February 22, 2011, 12:48 AM
If you are doing it to fit a custom chamber, fine, but if not, you are asking for a case head separation when you fire it.

Well yeah, do you think I would just be changing case dimensions for the hell of it? Let me re-quote myself: "This is being done to meet a certain OAL length requirement of a new cartridge I am developing."

Thanks k4swb, I'm pretty sure I can handle this with the full length die like you said. After all, it's not an extreme dimension change.

JimKirk
February 22, 2011, 08:43 AM
The part of moving the shoulder back can be handled by the die of the new cartridge(or a die of a similar cartridge)... but the shoulder angle formation will have to be fireformed.

I would trim to what ever would just fit the chamber ...fireform the shoulder and then do a final trim. All this assumes you have a chamber to work with.

Jimmy K

Walkalong
February 22, 2011, 10:25 AM
do you think I would just be changing case dimensions for the hell of it?
You might not be as clear as you thought from the perspective of the casual reader. You understand, somewhat, or you would not be asking, but some newbie reading this may not, and they need to understanding what is going on. Knock yourself out. :)

918v
February 22, 2011, 12:49 PM
I am shortening the neck of a case by trimming it 0.130". After I trim the neck down, I would like to gain some of the neck that was lost by pushing the shoulder down and increasing the shoulder angle. I would like to move the neck/shoulder junction of the case down by roughly 0.060".

This is being done to meet a certain OAL length requirement of a new cartridge I am developing.



Are you developing a .222 Short Neck? So you can shoot 80gr VLD's from the magazine? Too late! I already dun it.

JK.

You will have to have a custom reamer made and a custom sizer die made to your specs plus a case forming die set all of which will run you close to a grand.

GLShooter
February 22, 2011, 06:10 PM
Sounds like a short version of the 20 Tactical case. I move the shoulders back for it but also neck down at the same time. With a custom chamber it should do fine for you staying with the .224 bullet.

Greg

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