Anyone have first hand load experience that would share data on the 458 American or 458x2"? TIA, Packy

Well I will have one soon when my blank shows up, and here is what I am going to do.
The case capacity of the 458AM and the 45-70 is the same; 78 grains of water. I just weighed them.
So, I will just go to my manuals and pick the hottest loads (Ruger #1) for the 45-70 and use those as a guide. I will start with the lever action load levels and go up from there.
It is a belted 45-70, but built on a strong bolt action.
450 Marlin load data will be useful as well. After all, that is just a 458 two inch American with a long belt. Those are lever action loads.
Have fun.

Not firsthand, but from Ackley's Handbook:

300gr bullet, 52gr 3031 @ 2530 fps

350gr bullet, 50gr 3031 @ 2310 fps

A couple others are listed using HiVel #2, which we all know is NLA.

I am sure that Ackley didn't own a chronograph, but made up his load data in his head.
I do respect him though.

I cant recall the load for mine offhand, but when I initially started reloading for it, the guide basically said "see 450 Marlin". I have used that data since day one, and have had no issues.
Mine was built on a remington 600 action. Amazingly light, but with the recoil to match, and I will never part with it. A great little gun for packing in the mountains. I have used this caliber to shoot a cougar, two bison, and a black bear.

I always take anything from the "olden days" (including Ackley's data) with a grain of salt.

Years ago I had experience with the 450 Marlin in a custom bolt action. I'm going off memory now, since I have no notes.

The handloading for it was easy. IMO, it was a good cartridge with two caveats. Proper feeding was the issue I ran into. I had a Ruger short action barreled - it was initially a 350 Rem Mag, which I should have left alone.

The other issue is that IMO, it didn't have enough case capacity. Later, I re-purposed that same PacNor barrel to 458 WM on a longer Ruger receiver and solved both the feeding issue and the case capacity issue.

I hate to be negative about anyone's pet project, but frankly I wouldn't own a bolt action rifle in 458 American or 450 Marlin, and that's based on experience. The std 458 WM is super versatile, and can easily match whatever the 458 American does plus so much more - easily - and it FEEDS.

I have down-loaded my 458 to sub-sonic (trail boss) and practically everything between up to approx. 2500 fps with the 350 gr Barnes TSX. I'm serious - it's versatile, perhaps the most versatile of all the cartridges I've messed with, which have been numerous - and lots of fun too.

One thing I should probably mention is that my 458 WM is not a standard chamber. It has the short throat that is std for the 45-70. In effect it's a wildcat, and I've never shot factory ammo in it and never intend to. I had the barrel engraved "458 Win Mag Short Throat" specifically in case someone inherits this rifle, and hopefully they have sense enough to not try to run factory loads through it. It can easily be reamed out to the std long throat, and shoot the 500-510 gr factory loads. But I have no use for them and the short throat is much more useful for my purposes. I doubt that the factory loads with the heavy bullets will chamber, but I've never tried them anyway.

I have two...one on a SMLE 2A receiver and one on a Marlin levergun. I shoot 300-750 gr bullets(some single loaded), jacketed and cast, in the SMLE and 300-450(mostly cast)in the Marlin...just like what I shoot in my various other 45-70's and many of the same bullet/pressure loads.

As USUAL, loads depend on the pressure limits of the receiver, the bullet weight and the ACTUAL case volume.

I load the SMLE to ≈42-43 Kpsi(more or less), the Marlin to 450 Marlin pressures and COAL's of 2.62"(same as OEM 450 Marlin 1895 Marlin levergun limits). The SMLE chamber is cut with a 458 WM reamer and I use 458 WM cases cut to specific lengths to accommodate the various bullet lengths for a COAL of 3.05-.07" SMLE mag length...case volume varies from ≈75-90 gr H2O as does pressure ranges.

The American is a ≈70-75 gr H2O volume case...YOU have to determine the volume...the same/similar as 45-70, 450 Marlin and several other large bore cases.

I DON'T POST MY LOADS for obvious reasons but you can use data for the other cartridges AS LONG AS YOU RESPECT THE PRESSURE LIMITS OF THE RECEIVER YOU ARE USING....my 450 Marlin Browning BLR can be loaded to the same pressure limits as the other cartridges available for this rifle so I can load to a pressure/velo as the original 458 WM BLR which requires knowing slightly more than the average reloader.

For all intents and purposes the 458 American is just a short version of the 458 WM...obviously...and you can do with it the same as you could with other cases of similar volume or the same as is done the 38/357, 44 Special/44 Mag, 500 Special/500 S&W Mag...or other wildcats.

There is load data available online and on other forums. This is a very old wildcat and some of the data found in Ackley and other "ol' timey" sources are valid, some isn't...no different than todays and with any other cartridge...BS is BS no matter the date or cartridge. If you are going to muck around in this house you need to use your head...samo-samo as in yesteryear.

I've found the 458 American to be just as effective as the "ol' Thumper" or the "new Thumper, the 450 Marlin", does the same job, kills just as well as long as you put the bullet where it belongs and hurts just a good as ANY 45 cal relatively large cased cartridge in a light rifle with regards to recoil.

If you want to wring the most out of this cartridge use a L.A. bolt gun receiver so you can utilize the extra pressure limits and seat out to utilize maximum case volume.

As usual again...in todays world there are other larger volume cased wildcats that make the 458 American "slightly" obsolete and if you are going to wildcat, you might as well go bigger if possible...ALWAYS ARGUMENTATIVE to say the least.

Good Hunting

I think the 458 two inch, is a perfect cartridge for North America; just as the 45-70 has proven to be; after all, they are essentially the same; it is the rifle that determines the loads.
Most NA hunters do not need, nor can they handle, a full 458.

quote:

Most NA hunters do not need, nor can they handle, a full 458.

I'm one of those.

I have shot a 458 WM with full factory loads, in a different rifle, and I swear I thought the damned thing dislocated my shoulder. but I shot it again anyway.

But my light 458, with some of my handloads kicks rather stiff, but I worked up to it. I have no need for such loads anymore.

Packy,
my 458x2" is built on a Mk10 action with a block in the magazine, longer then a short action, but shorter then a full length magazine. It's very easy to just pop in rounds without having to slide them to the back of a full length mag box.
300 grn bullet 55 grns IMR 4198 gives right at 2400 fps

400 grn 51 grns 4198 and 2100 fps.

Rifle has a 20" barrel and .650 at the muzzle and an old Garret lt wt stock. You don't have to look at the empty brass to know if they went off, but is very nice to carry.

quote:

my 458x2" is built on a Mk10 action with a block in the magazine

That seems to be the right combo to me. Good performance too. I've heard of success with the std Mauser action, with the feed rails modified. But I'm more into sure things nowadays.

I made a big mistake in assuming that the short action with the mag bolt face and proper follower would feed and went ahead and had it barreled in 450 Marlin. Then I tested it and found it would not feed correctly.

Disappointment set in.

My 458 was made with mostly carrying in mind. It's relatively light and short with a 20" barrel.

Trust me; a 98 Mauser will feed the 458x2 or Marlin, correctly if you mill the feed rails correctly; you can't just put a barrel on one.
Whomever did your work must have skipped that part.

That "if you mill the feed rails correctly" part is the hitch.

There is a lot to deal with on some actions and for some cartridges. The follower, the feed ramp, the breech, in addition to the rails.

On my experiment with the 450 Marlin on a Ruger stainless action originally a 350 Rem Mag, one would think feeding the 450 would be a non-issue. The follower, bolt face, mag length, were all correct to start with. As it turned out the feed ramp needed mods and the rails too. I sent it to a gunsmith who was a Mauser specialist, and said he had extensive experience at getting an action to feed. When I got it back, it was better, but not slick - still flawed. I got rid of it.

I've been down the road of making it feed several times. There were a few successes, and several failures. So, I learned the expensive way to not go too far astray from what an action was feeding originally.

I had a Ruger 77MKII rebarreled in 6.5 Grendel. The action was off a target rifle originally chambered in 6mm PPC. It had the magazine block, the correct follower, the correct bolt face from the factory. It works, but not perfectly. If I put three cartridges down in the magazine, and one in the chamber, it will feed nearly perfectly, and I've decided that four rounds are plenty, although it will hold five.

It is the only rifle that I own now where I've compromised on feeding, and with the 6.5 Grendel, only slightly.

On my 458WM, I used a stainless Ruger 77MKII action that was initially a 300 WM. Luckily, it feeds the 458 with no mods to the feed rails or feed ramp. I changed the follower and the magazine box, and that's all.

The Ruger, and most other modern bolt guns, use the sheet metal mag box to make them feed; not the receiver rails (yes there are exceptions. So, all you need in many cases is to bend the lips a bit. Not like old school rifles like Mausers; the feed lips are machined into the receiver.
Beware of self proclaimed Mauser, or any other, "expert". That is why I (from long ago) do all this myself; bad experience with so called smiths and experts. There are fewer good ones than you can count on one hand in the U.S.
But it is not rocket surgery; you follow some basic tenets and you can make most anything feed. For some of the very large cases you ideally should buy one of the custom $450 bottom metal; that makes it easier.

I just took another look at my 458 on the Ruger receiver, and it surely appears to be feeding off the rails, rather than the magazine lips. The Ruger has the sheet metal magazine box but it appears to play little or no role in feeding. There is a slight ridge at the top of the box which may play a part, but it does not extend out beyond the feed rails. I think the Winchester mod 70, for example, feeds off the magazine lips.

The magazine box in my Ruger is not original. The sheet metal bowed out in front from the recoil on the original. I bought a box for the 416 Ruger, directly from Ruger parts, and it fits perfectly, and has not bowed out. I presume it's tougher to stand the recoil of the 416.

Just FYI, I have no intentions of getting myself into a project that requires messing with feeding issues, feed rail, mods to the receiver, etc. I know how to avoid all that, and intend to do so. If I ever have an action rebarreled again, it will be chambered in a cartridge that feeds perfectly with no mods to the action. I'm done with making it feed.

The sheet metal boxes of the M70 and 700 do not extend beyond the receiver rails either.
Making different actions feed with cartridges for which they were not originally designed is a necessary, integral part (and fun) of the custom rifle game.

I do not have a Mod 70 on hand to look at, but if my memory serves me, it feeds off the lips of the magazine box. I can see no way for the magazine box on my Ruger to have the guidance effect as a substitute for the feed rails.

And I respectfully disagree with your assessment of necessity, and in my experience it was fun to dream up projects, but IMO it is not an integral part of the fun to try and make something work outside its original design.

If wasting a bunch of time, setting yourself up for disappointment and compromise, and spending a lot of money with gunsmiths on something with no guarantee of success is satisfying and fun to you, go for it. I've been there - done that, and it wasn't nearly as much fun as having a no muss or fuss rifle that functions properly and feeds perfectly.

I've had a bunch of Mausers over the years, all sorts, military and commercial. After having too much "fun", per your definition, I finally decided the 8x57 solves a lot of feeding issues. I still have two in 8x57. My favorite is a carbine built on a CZ 550 action I bought from Brownells when they were available. The other is on a Mark X Mauser action, with a three position safety and custom trigger and custom barrel. Both feed perfectly, and required no modifications. I also have a substantial quantity of 8x57 ammo. A few years ago I bought a whole stash of Lapua ammo with their 200 gr RN bullet. I think it's the MEGA. I have never seen it before or since for sale anywhere. Both rifles shoot it accurately. I've shot several hogs with it, and it's satisfyingly overkill.

I would far rather experiment with handloads, than messing with actions out of their original design purposes. Never again.

However, I do understand the idea and "fun" of experimenting. I just learned the hard way to stay within certain parameters. For example, I've owned several wildcats over the years, and have two now - three if my 458 is technically a wildcat, since it has a short throat. I have a 9.3mm on a necked up 338 WM case, and a 323 Hollis, which is the 308 Norma Mag necked up to 8mm. The 9.3/338 is on a Ruger action, and the 323 Hollis is on a CZ 550 that was initially a 7mm Mag. Neither action required modifications and both feed perfectly.

Both rifles are superfluous, of course, but I like them a lot. For my needs and uses now, they are excessively powerful, but I am developing moderately reduced loads for them and will use them sometimes for deer and hogs.

You don't understand; I don't pay anyone to do anything for me; I do it all myself.
Few out there fully understand what, and how, to make rifles work with different cartridges. Those who don't should stick to known combinations.
Come over and I will show you how each design of rifle feeds cartridges. Model 70s, post 64, still use the receiver rail and box combination to feed. Pre 64s, are different.

I understand that you have the capability to do much of the gunsmithing, if not all, yourself. That makes a big difference, and is commendable.

I now have the desire to keep gunsmithing to a minimum. It wasn't always that way, and thus I had to sort through those who made claims they couldn't or wouldn't fulfill, all at my expense of course.

Thus, I have little desire in gunsmith work that requires special tools and machinery, and little desire to sort out real gunsmiths from the imposters.

So, you are correct, I'm one of those who "should stick to known combinations".