Reloading and making 458 win mag

[logandrut]

I had an interesting weekend with a fellow CGN member and started working out my process for reloading this classic cartridge. I just wanted to share what worked for me and I'm very interested in what has worked for you.

Resizing brass:
A few 300 and 338 win brass were manually resized, some was able to be loaded and fireformed while some was plugged in the following manner and fireformed. Remington 9 1/2 M large rifle magnum primers, unique pistol powder, a small square of cotton cloth poked down on top of the powder, filled up with cream of wheat (instant packets) to bottom/middle of neck and then plugged with soap.

2 batches were tested using ww super 338 win mag brass, x12 with 20 grains of unique (of which, 2 failed fireforming by cracking necks) x12 with 25 grains unique (only 1 failed) I think not achieving a full and complete soap plug may have caused cracking??

Reloading 325gr Hornady FTX:
Using once fired hornady 458 win brass, I did 3 batches using benchmark powder. X3 each @ 74, 76 and 78 grains. The 78 grain loads were seated slightly ahead as to not compress the load. As I understand, shooting it in a #1 that shouldn't matter. These seemed to pattern the best but further testing is of course required.

Im curious what those of you who know, think of my process here. Any tweaks that could improve results? I was okay with 27/30ish fireforms, is that average?

The picture is of factory loaded Hornady 500gr DGX beside a 338 win after fireforming and a 325gr FTX projectile.

 

[BLCB]

Wtf is with COW for fireforming?

 

[logandrut]

Wtf is with COW for fireforming?

Dense enough to provide pressure on the case, soft enough not to damage the case? Just guessing. What else works?

 

[BLCB]

Dense enough to provide pressure on the case, soft enough not to damage the case? Just guessing. What else works?

A fast powder. Just that, maybe some dacron for the tougher stuff. I shoot guns for food. I don't shoot food for guns.

 

[dcalf]

Cream of wheat is very common and historically used in fire forming. As logandrut says it is also self packing.

 

[257hunter]

What were the failures on the cases that didn’t work? You are moving the material a lot so annealing at some point in the process may help. (I had about the same failure rate forming 30 Gibbs from once fired cases, after I started annealing them I stopped getting any splits) I also use cow for fire forming. Those ftx might be pretty fragile at 458 velocities, might be fine for your use case but personally if I’m using a cartridge that big I’d want a more sturdy projectile.

 

[Dean2]

I have necked up lots of brass. Do it in stages. So if you start with 338, neck to to 375, then to 416, then to 458. All you need is the sizing dies. In fact you can get away with just using the stem and increasing expander balls in the 458 die if you don't have the other dies. A whole lot easier than fire forming. Anneal before you start and press the expander balls in gently using lots of Imperial sizing wax on the ball and brush/lube the inside of the necks. If you keep fire forming, anneal them first too

 

[logandrut]

What were the failures on the cases that didn’t work? You are moving the material a lot so annealing at some point in the process may help. (I had about the same failure rate forming 30 Gibbs from once fired cases, after I started annealing them I stopped getting any splits) I also use cow for fire forming. Those ftx might be pretty fragile at 458 velocities, might be fine for your use case but personally if I’m using a cartridge that big I’d want a more sturdy projectile.

Comparing the 300 and 350 grain datas and picking a mid range in between, I think the 78gr load will be pushing them to about their limit. A few people posted on here or online Hornadys reply when questioned was 2500 fps max. Ill keep it in mind about the annealing too, thanks.