.338 from 7 mm mag - tutorial resource?

[huntinlever]

Hi guys, looked for it but so far no real step-by-step process. In the absence of .338 brass, looking to learn about re-forming from 7mm mag. Could someone point me to a pretty thorough breakdown of the process?

[15meter]

Same case length right? 7mm will chamber in the 338 with no issues right? If so, sounds like a candidate for fireforming.


Try here:

https://castboolits.gunloads.com/sho...ng-458-Win-Mag

May point you in the right direction. I've fireformed a number of different cases. I typically use recycled primers from screwed up cases, ammo of unknown provenance that has been given to me. I've even used 50+ primers that were underwater in a flooded basement for an unknown length of time. Every one went off when fireforming.

Pistol powder, toilet paper, corn meal and wax are your friends. Fire vertically and you should have instantly formed cases.

[missionary5155]

I concure with 15meter !
And that "Fire vertically" is very important. Do not fight gravity. Use it.
Our last fireforming was using 9.3x74R to make 50-100. Straight up all 50 shots which had to swell out dramatically and did.

[Teddy (punchie)]

No oily casings when fire forming. Yes casing need to be in the chamber just right or can show pressure signs. 95 percent of the time you'll have no trouble. Use a good mid pressure load.

Read about Ackley and fire forming.

[pworley1]

I form mine on the press. You can just lube and run them in the 338 sizer die by starting the sizer die only a couple of threads in the top of the press and turning it down a few threads after each stroke, redistribute the lube often. This is a slow process but it usually produces very good brass with few damaged pieces. If I am making several pieces, I will Lube them and run them through a 300 win mag expander, then a 8mm expander and finally the 338 sizer with the expander installed. Three strokes to produce load ready brass. Be sure to anneal before firing.

[huntinlever]

Good start. Thanks guys. New to .338, I'd vastly prefer to work on one set of variables at a time but in the absence of brass, I've always been intrigued by the option (same would go for my son's vintage 38-55, from 30-30 brass).

[15meter]

Good start. Thanks guys. New to .338, I'd vastly prefer to work on one set of variables at a time but in the absence of brass, I've always been intrigued by the option (same would go for my son's vintage 38-55, from 30-30 brass).

30-30 to 38-55 was one of my first forays into reforming brass probably 15+ years ago. It comes out short but perfectly functional for plinking and practice.

That was where I learned the fire vertically trick quite by accident. I had shot several horizontally and had lumpy misshapen cases. I was getting frustrated and popped one off at probably a 60 degree angle and it was almost fully formed. Next one was straight up and had a perfectly formed cases. Plus the next hundred.

[stubshaft]

I would anneal the necks and run it over a 30 cal expander than FL size in a 338 die.

[BK7saum]

Be careful with annealing. if you anneal the neck and shoulder, the case can collapse. As long as they aren't splitting on you, I would anneal afterward. If you get splits, then a light annealing before can be beneficial.

I wouldn't do anything with a whole batch until you determine which order or method works.

[stubshaft]

Anneal before necking up and after necking down.

[huntinlever]

Thanks guys. I actually just picked up 100 cases from Scheel's, so that's one variable I won't have to worry about for awhile. But I appreciate the info and will see if I can't find some 7mm, just to learn.

[MostlyLeverGuns]

Lee has tapered expanders (MidwayUSA) that can be used to expand case necks. Lubricate INSIDE case neck, then Lee .338 tapered expander, then size in a .338 die, or just use a LEE .338 Sizing die. I believe the LEE dies have the tapered expanders.

[huntinlever]

Sorry, delayed in saying thanks guys. I've decided to try and gather some new .338 brass over time, a kind of prudent desire to limit variables for now on a new cartridge. I better understand the case forming process and options now and will try it out once I get a handle on loading this round. Appreciate it.