I am planning to ream my 458 Win 98 Mauser to .458 AR, so I have several questions I hope can be answered here.

1. Where can I get the reamer?
2. Where can I get brass?
3. Where can I get dies, including a neck only die?
4. Is there a 375 RUM / 458 AR conversion die (After initial trim)
5. Has anyone tried fire forming a Ruger 375 case?

NRA Life / Endowment Member

First, PM Jeffeoso. The AR cartridges are his babies, and any info you need he will have.

http://forums.accuratereloadin...4711043/m/769108843?

Did I mention talk to Jeffe?

Dave Manson has the reamer print and makes great reamers.

Quality Cartridge has brass if you don't want to make it.

C4HD lists the dies. Others may too. A neck sizer will probably be a custom order in a .458 anything, but any die maker could make one.

I don't think you need a forming die. Push the shoulder back, fire a fireforming load with a .375 bullet, then trim and finish sizing.

The Ruger is a smaller diamter case than the RUM or parent .404. That would be BAD and void your warranty. Possibly void some fingers and an eye as well. The Ruger is a uniquely sized case that is not compatible with the RUM.

Might lose one round in the magazine. The RUM case is fatter than the belt on the Win Mag. Otherwise, some feed work, and it will work.

Jeremy

OK, I get it.

Reamer first though. Once I get a fired case I can send it to Hornady and they will make the dies as well.

Do you know how I might reach Mr. Dave Manson?

PM him here, or mansonreamers.com 1-810-953-0732 (tel)

Jeremy

quote:

Once I get a fired case I can send it to Hornady and they will make the dies as well

While I have used Hornady for custom work last time I contacted them they said there were not taking custom at that time.

CH4D makes good dies and has dies set up for Jeff's design. http://www.ch4d.com/products/d...caliber&filter=458ar Just curious why you want to go through all the extra steps?

I have been a member of the Hornady web group since they were experimenting with the FTX Bullets. I doubt they really know me from Adam though my pictures were among the first FTX kills. They said they have made these dies for several people but the were all a little different. So I figured a fired shell would give them the results of my chamber effort. If I can get a ready made reamer and avoid using a 375 Rum reamer etc. then perhaps I can use the dies you suggest. Hopefully so.

Thank you for the contact!

Do you want to hunt dangerous game with this rifle once converted? The first concern I would have would be the vagaries of cartridge feeding when calibres are converted.

No matter how powerful the rifle becomes, it may not help if you can't feed a second round in a hurry.

The answer is yes, Cape Buffalo. The feeding issue is real, I know. I cannot feed full length 458 3.34 shells as it is. I can feed 3.26 to 3.30 very well. That's why a Lott won't work. I know these are max a 3.35, however I will be at 3.26 to 3.29 and will not reach the full capability of the chamber. However, I will be in the Lott capability. The 458 AR round has the same bolt face requirements and this is a claw extractor as in very nice 98 Mauser. Reports from others do not list any feed problems per say. I will not be able to fit as many shells, down by one.

quote:

I have been a member of the Hornady web group since they were experimenting with the FTX Bullets. I doubt they really know me from Adam though my pictures were among the first FTX kills. They said they have made these dies for several people but the were all a little different. So I figured a fired shell would give them the results of my chamber effort

I have nothing against Hornady custom. I have about a dozen sets. If they are taking custom orders again great. Looking at the price they are pretty much the same as the CH4D. I thought there was a 458AR reamer floating around here. Or at least in a smiths hands. Talk to Jeff

I wonder how much they view the chambers as different? I have a custom set right now that they built for me. I switched to a different brand of brass and my dies no longer give me enough neck tension.

Anyway Welcome and enjoy your project.

Howdy,
just got back from the UK...
its an easy conversion, and if i can find my reamer, i'm happy to rent it to a gunsmith -

dies -- hornady custom are great, i'd place an order "now" CH4D makes a good product too

to fireform, take 375 rum cases and remove the expander from the dies --- set the die to much just enough shoulder to close the bolt and fireform, THEN trim --

can order brass from qualcart or via midwayusa

happy to talk on the round, it's a durn fine 45

can't use ruger brass for a 458 AccRel.. too small base

The Smith is looking for one and I am sure even renting the reamer from you would be a help, if you can find it, heh.

Hey I hear ya on the 375 Ruger, but I thought the base was the same size as the 375 HH and the 458 Mag. I see the Rum is 2 thousandths larger. I was going to try it after pressing the shoulder down a tad with a few grains of pistol powder, some filler and a wax cap just to see if it would split or not. Guess I won't though.

The 458 SABI or otherwise called the 458 African was my backup idea, but I think the 458 AR is better because it takes less metal off my receiver! I don't need or want 460 power.

375 RUM brass has gotten very scarce, so I guess I will just get some brass from your source.

Thanks Jeff, for piloting the Wildcat. Perfect for a Mauser 458 Win upgrade.

I will not actually do this until after my upcoming Safari, as I don't really have time to get it done before.

quote:

Originally posted by Michael Sperry Sr:
The answer is yes, Cape Buffalo. The feeding issue is real, I know. I cannot feed full length 458 3.34 shells as it is. I can feed 3.26 to 3.30 very well. That's why a Lott won't work. I know these are max a 3.35, however I will be at 3.26 to 3.29 and will not reach the full capability of the chamber. However, I will be in the Lott capability. The 458 AR round has the same bolt face requirements and this is a claw extractor as in very nice 98 Mauser. Reports from others do not list any feed problems per say. I will not be able to fit as many shells, down by one.

Thanks Michael, the background to my question was spurred by this article, which you may know of already:
https://www.africahunting.com/...oficiency-exam.2604/

I know that buffalo can be tough and dangerous. My PH in Mozambique had a 458 Lott but wanted more and had a .550 magnum made up on a Brno action. I worry about 'African shortstroke' more than lack of power, however, and would prefer the shortest reliable action available, able to hold the most cartridges without requiring an extended magazine, which is harder to carry one-handed.

Am back from my trip, what a rush at times. Other than hunting and taking five of Africa's beautiful animals, riding through the bush on an Arabian stallion was one of my favorites.

So I am back on the 458 AR quest. Having learned first hand how tough a Rolland Ward Blue Wildebeest is and having seen some rather intimidating Cape Buffaloes that make that huge blue seem small, the idea of upping the 458 Win Mag is even more appealing.

Anybody got a reamer? I emailed Dave Manson and am waiting for his reply. It's Saturday though, so probably won't hear until Monday.

I wish you the best and am sure that Jeffeoso will help you out.

If I had a 458WM and a little time I would do an AR. (I have a 500, but that for that you would need a re-bore.)