Fire forming virgin brass for bottleneck die setup - how stout?

[huntinlever]

I've never done this particular process before but will be trying to set the shoulder back on my .338 brass and will be doing a run of 5 rounds on new Winchester .338 Magnum. I'll be using the RCBS Precision Mic and process learned from another member, and what I've been researching online.

The bullet is a Speer 200 grain Hot Cor, Rem 9 1/2 LRM primers. I have some Ramshot Hunter, and will also be picking up some IMR 4350 and 4831 next week. Per Lyman's 51st, I'd thought to use the Hunter, with 66.3-73.7 gr powder listed.

I'd thought just a minimum load would be adequate to get proper chamber fill for this purpose. I've since seen some say "moderate," and some recommending "pretty stout" load level, to get proper chamber fill.

For this purpose only - no load development yet, just fire forming a few cases to set sizing/expander die - what level load do you guys use?

[huntinlever]

Mods, I'd forgotten I'd asked this question in another thread. Sorry for the redundant bandwidth. Please feel free to delete at your judgment.

[pcmacd]

I've never done this particular process before but will be trying to set the shoulder back on my .338 brass and will be doing a run of 5 rounds on new Winchester .338 Magnum. I'll be using the RCBS Precision Mic and process learned from another member, and what I've been researching online.

The bullet is a Speer 200 grain Hot Cor, Rem 9 1/2 LRM primers. I have some Ramshot Hunter, and will also be picking up some IMR 4350 and 4831 next week. Per Lyman's 51st, I'd thought to use the Hunter, with 66.3-73.7 gr powder listed.

I'd thought just a minimum load would be adequate to get proper chamber fill for this purpose. I've since seen some say "moderate," and some recommending "pretty stout" load level, to get proper chamber fill.

For this purpose only - no load development yet, just fire forming a few cases to set sizing/expander die - what level load do you guys use?

You want a MAX LOAD of propellant for this. Pistol powders are fast and ideal for this work.

I've even used no projectile with Cream of Wheat atop the charge to fill the void, and then put a cork plug in the mouth, waxed in place. This only works with VERY FAST pistol propellants. Bullseye and the like.

It works GREAT for taking 220 Rooskie to 6 PPC. Get a large jar lid, cover the bottom with 1/8" thick melted wax, and while hot put some 1/8" cork atop this. When the wax hardens you can turn the lid upside down to your round to "cookie cut" the plug with the prepared case mouth.

Anneal the cases down to where the new shoulder will be if you want long life from your brass, both BEFORE and AFTER you resize it.

[Willbird]

You can actually do some of the job just using the reloading die in the reloading press if you buy or make a snug fitting plug that fits the case mouth when the press ram is all the way up.

Hornady makes and sells custom dies to do this.

https://www.accurateshooter.com/technical-articles/hornadys-hydraulic-case-forming-dies/

Same general idea as Hydraulic decapping but we want to keep the primer IN so will need something like this.

https://www.butlercreek.com/dies-and-shell-holders/single-stage/extended-shell-holder/292.html

I am playing around with a 243 reformed into 6mm creedmore neck and shoulder for an AR308 and the process worked OK for me for one case anyway.

The bottom case had it's shoulder hydraulically formed by the process I describe. I used marvel mystery oil as the hydraulic fluid but water IMHO should work fine as well.

https://i.imgur.com/nN3xLDa.jpg

I have a gage pin set but if you do not you could size a case, and then subtract .0016" to .002" from the measured inside dia of the sized but not expanded case neck and get an idea what size gage pin you would need. If you have a lathe or have a friend who does they could machine a punch/piston for you. You just fill the case with fluid and wack the punch with a hammer to form the case.