Home Forums Hunting & Shooting Express Rifles and Big Bores Only 458WM COAL and loading

I just saw the last few posts from the various Knights - for some reason the forum was not notifying me of new posts. Thanks again for all the help, and I would be honored to sit at the square table. I don't actually have any meaningful 458 experience to draw on though, so a poor addition I would be. My first 458 should arrive next week, and I have about 160 rounds from Federal to run through it. By then, I hope to have some powder and primers in hand to start reloading the 404 hammer, which really does seem like a great do it all bullet.

Has anyone used the 404 on big game yet? Buffalo even?

So I can change my Model 70 to load to 3.585" COAL with a .375 H&H mag box, follower, and bolt stop, which will change my action and mag well to 3.6" from 3.4". I have five questions to add to the pile over the last week:

The ejector and boltstop are two separate parts needed, both shorter on the .375 H&H action.
This times the ejection for when the bolt stops at the more rearward withdrawal set by the boltstop.
Don't confuse the rotating claw extractor with the fixed ejector residing there beside the boltstop.

1. Can you confirm that the factory chamber in the FN/Winchester 70 Safari will accommodate the extra 3.585 - 3.340 = 0.245 in of COAL?

The SAAMI .458 Winchester Magnum chamber will accommodate longer COL than a SAAMI .458 Lott chamber will. Any COL with a bullet that is not touching the rifling in a .458 Lott
will have even more room to spare in the .458 Winchester Magnum loaded to same COL when bullet length is long enough to allow that.

2. Will SAAMI 3.340" cartridges bounce around in the bottom of the magazine well enough after a few top-ups to move the bullets in the cases under recoil?

As Forrest Gump said, "It happens." But not with a properly loaded round, 100 to 105% net fill and a good crimp on a good, recoil-stopping cannelure or groove.

3. Would it be fine to load to the same 0.2" spread between the magazine boxes i.e. 3.540" to leave the same slop in the magazine? If so, can I use the same loads as in SAAMI spec reloading manuals, but with the bullet out 0.2" to have uncompressed loads? Would I get the same velocity at lower pressure, given the same powder charge?

Of course you can, as long as you keep most powders over 85% net fill, and H4895 can be used down to 60% of a maximum load with your particular bullet.
Different powders react differently. Some will show decreased pressure and velocity, but some may actually increase pressure and velocity when de-compressed.
See my latest post on the .458 WinMag Mega Thread. Sort of like "Mega MAGA" is to good people, so is that thread to the .458 Winchester Magnum.

4. If the magazine box difference between .458WM and .375 H&H is only 0.2 inches, does that mean the difference in bolt throw between standard length (.30-06 SPRG, .458WM) and the .375 H&H is also only 0.2 inches?

Yes it is only about 0.200" different, maybe as much as 0.250" (I have not measured precisely) difference in bolt throw, but absolutely only 0.200" difference in mag box length.
This points up the silliness of putting a 0.300" longer cartridge case in a rifle that is only 0.200" longer in mag box, i.e., the .458 Lott.
You have to trim the .458 Lott brass short to make some bullets fit inside a 3.600" COL when they work as is in 2.500" brass with a 3.340" COL, per SAAMI.

5. If I'm handloading anyway, would the 450 grain Swift A-Frame at 2200 fps in a factory SAAMI 3.340" length do everything that a 500 grain A-Frame would at 2150 fps at 3.585"? If so, would the same apply to solids? I'd go as light as I could reasonably get away with.

As others have said, you can stick to SAAMI .458 WinMag loads at 3.340" max COL and 60,000 psi MAP if that is all you want to do.
2150 fps with 500-grainers and 2200 fps with 450-grainers is easy-peasy with sub-maximal loads in a SAAMI .458 WinMag with 24" barrel.
Long monometal brass solids are a different kettle of fish,
but 2300 fps with the CEB 450-grain brass Safari Solid will do +2350 fps in a factory .458 WinMag M70 Winchester with the usual +3.4" mag box.
COL might be as much as 3.360" and pressure might even be a tad over 60,000 psi, but not much.
That solid load will not be beat by any other heavier solid, in whatever rifle, IMHO.