458WM in 98 Mauser action

[billw]

I'm putting this rifle together this week and hope to shoot it next week. I shoot cast bullets exclusively, some are NGG--no grease groove. The rifle is a substitute for my Trapdoor testing. I will be forming brass from 7mm Mag and 300 WM brass if anyone can give me methods for doing that. I will open necks with 30, 35 and 45 expanders with anneal/stress relieving between steps and/or just fire forming with fillers and pistol powders as I have done with other brass in other calibers. My load data will be similar to my TD loads with pistol powders and some fillered loads with rifle powders. I am well aware of pressure spikes and will avoid that. My intention is to shoot at subsonic and as high as 1500 fps at a maximum velocity.

[Bass Ackward]

I will be forming brass from 7mm Mag and 300 WM brass if anyone can give me methods for doing that. I will open necks with 30, 35 and 45 expanders with anneal/stress relieving between steps and/or just fire forming with fillers and pistol powders as I have done with other brass in other calibers.


Bill,

Sounds like you know what you want to do and how you are going to get there.

Let us know how you make out expanding the brass. I usually end up way short comparred to where I am supposed to be using the expanders. I have better luck with a fillered load when going that far and then using the 45 expander.

I hope you got your hands on a reamer with a throat configuration that will benifit what you are attempting to do.

[Larry Gibson]

Let me know when you get it built as it will be interesting to compare your TD loads out of the bolt gun compared to my TD loads out of my Siamese Mauser.

Also some years ago I reformed a couple hundred .338 mags to .458. I also went with a filler load to blow out the case as Bass did. Anneled the cases first then used Bullseye and COC with a touch of dacron to hold it in. I don't remember the exact amount of Bullseye but I worked up to it until the cases just formed. I didn't lose a single case with that method. Be careful though if you use this method as the muzzle blast with all that CO is still dagerous at close range.

Larry Gibson

[billw]

Bill,

Sounds like you know what you want to do and how you are going to get there.

Let us know how you make out expanding the brass. I usually end up way short comparred to where I am supposed to be using the expanders. I have better luck with a fillered load when going that far and then using the 45 expander.

I hope you got your hands on a reamer with a throat configuration that will benifit what you are attempting to do.
The expanding process is rather difficult; I'll go with fireforming with fillers. The finish reamer is made for the 500 gr FMJ JB. I will look at it carefully but will go with it since it was a loaner from a friendly gunsmith and "no fee" member of my club I own.

[billw]

Let me know when you get it built as it will be interesting to compare your TD loads out of the bolt gun compared to my TD loads out of my Siamese Mauser.

Also some years ago I reformed a couple hundred .338 mags to .458. I also went with a filler load to blow out the case as Bass did. Anneled the cases first then used Bullseye and COC with a touch of dacron to hold it in. I don't remember the exact amount of Bullseye but I worked up to it until the cases just formed. I didn't lose a single case with that method. Be careful though if you use this method as the muzzle blast with all that CO is still dagerous at close range.

Larry Gibson
COW and cornmeal fillered loads for fireforming will blow a hole in plywood. Fillered loads with a bullet will sandblast a Chrony. I know; my Chrony is sandblasted--and shot as well but still working after a personal rehab.

[Nardoo]

Hi Bill,

It depends a bit on what kind of brass you are using as some seem better suited to being fire-formed or necked up without splitting than others. I often turn 7mm Rem mag brass into .338 Win mag cases with one pass in a .338 wm full length size die. Using Remington brass I have 100% success. Winchester brass is next best but occassionally splits the necks. I do not worry about annealing.
I also make .375 Win cases out of PMC 30/30 brass by fire forming with 10 gns of Red Dot over a case full of Wheat-hearts (we do not have COW in Australia). I did 300 cases in my back yard recently without losing a single one. I was very pleased as I only used the PMC cases as they were by far the cheapest and I had accepted that I would inevitably loose some to splitting. Tried it with some Highland cases and lost 6 out of 20. Not sure if it is because the brass is softer or somehow has better elasticity. Good luck with your project. By the way, check out Jim Allison's moulds from CBE in Australia. He has some fantastic 45 cal rifle moulds and a few specifically for the .458. He is a pleasure to deal with and will return your email questions as soon as you send them. His moulds are superb to use and will be cheap for you guys in the US with the present exchange rate.

Nardoo

[billw]

Nardo,
Thanks for the reply. I will fireform 300 WM first, then try the common 7mm Mag. I use cornmeal now that I can't find granulated COW; the flake type does not fill well and is much more difficult to pour into a neck. I stress anneal with a grain alcohol flame rather than anneal with a propane torch.
I have a number of moulds and 2 custom ones I used in my Trapdoor. I am looking at the Lee 500 gr spire point as a possibility. These loads will be low recoil and lo-vel just to test lubricants and alloys, the same as was done in my TD.

[lar45]

I like the expanders in Lee dies. They are long and very smooth with a gradual taper.
I was able to take 300 Win mag cases and neck them up to 416 Taylorby going .338, .358, .375, .416. I only did a few, but didn't loose any.

I tried fireforming some 30-30 improved cases(12" TC) with a wax plug and some Unique. I put several layers of old denim rags over the muzzle, then a tin can and finally a board on top of it all. I tried this in the basement and figured it would be fine. The wax plug shot through everything and blasted a flourescant light in the celeing.
The wife was most definatly not amused.
So the lesson here is to do it outside and treat them with care.