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

I've been reading up on the great 458, and have a couple of questions if you don't mind. I believe I understand how the longer throat of the WM allows for a longer COAL than something like a 458 Lott. What I don't understand is how people are taking advantage of that in magazine guns. Are you single loading them, or do your guns have longer mag boxes than the M70? Thanks very much.

The CZ 550 magnum has a +3.8" box length.
The Ruger No. 1 is unlimited in magazine length, of course.
The 500-grain TSX can be loaded to 3.780" COL and be barely off contact of rifling in a SAAMI .458 WM chamber.
It will not fit at that COL in a SAAMI .458 Lott chamber.

Earliest CIP homologation for the .458 Lott had the same throat as the SAAMI .458 WinMag, tacked onto the long-brass chamber.
Subsequently CIP corrected the homologation to match the short and tight throat of the SAAMI .458 Lott.

So, one can find the early CZ 550 Magnum .458 Lott with the long throat,
and those rifles will give lower pressures and lower velocities with factory .458 Lott ammo than is expected.
The supposed 2300 fps (500-grainer) loads in such a rifle may not crack 2200 fps MV.

The longer-than-SAAMI-governed COL in the .458 WinMag:

Many supposed standard mags are actually +3.4", like a Ruger M77 MkII, Hawkeye, etc.
The long-action M70 box is +3.6" inside length.
The CZ 550 mag box is +3.8", Dakota M76 African, etc.

I have 400-grain loads that are 3.395" COL and +2500 fps and they work fine in my standard-length magazine boxes.
Many standard-length magazine rifles will eject a loaded, unfired round of 3.54" COL,
with no alteration of ejector timing, etc.
They may be single-loaded off the top of a magazine full of SAAMI compliant ammo:
500-grainers at +2200 fps and 3.275" COL in the case of Federal TBSS, etc.

Some may cry foul at that, but I say it makes your rifle like 2 rifles in one:
A single loader for precision longer range shots,
plus a stopping rifle repeater for close range work.
Ammo carrier on buttstock or belt full of long COL-loads,
magazine full of short-COL loads.
One shot with the 404-gr Shock Hammer at 2500 fps will usually be all that is needed, near or far.

Thank you. I think I'm tracking now. A standard M70 in 458WM has a 3.6" magazine? I thought they were shorter for some reason.

I do have a CZ magnum action that could be built up into a nice 458 rifle. Of course, the reason it is 3.8" is because of the 375 H&H, I assume. I would prefer to keep the bolt throw shorter when possible.

Any thoughts on the Blaser R8? Mag is long enough for Lott, but you could just get the WM barrel instead. Should feed or shoot just about anything, I would think.

From another thread, it sounds like you have to alter the bolt stop and unblock the magazine of an M70 in order to get to 3.6". Is that correct? How difficult is that to do?

Yes, that is correct.
Remove the block at back of magazine, or order an inexpensive .375 H&H-length replacement box.
Shorten the existing ejector/boltstop yourself, or order the .375 H&H-length replacement part.
You do not have to shorten the rear bridge and open up the ejection port rearward.
It will eject 3.6" COL ammo easily without that being done.
No milling of receiver is needed.
Loading the ammo into the ejection port simply requires backing the rear of the cartridges into the magazine,
natural way to load them anyway.
Having the port short is no hindrance to loading.
Having the bridge left long allows the longer spacing between rear scope base holes to be preserved.
Allows a stronger bond with JB Weld when rear base is glued, greater surface area epoxied.
And the rifle just looks stronger with a bigger ass on the action, haha.

The Blaser R8: I know nothing about them. But if they have a 3.6" magazine capacity,
then one with a barrel chambered for SAAMI .458 WinMag
will put the SAAMI .458 Lott barrel to shame.

Thank you very much Sir Ron, I am on my way to increasing my 458 enjoyment thanks to you. Now if that M70 would just arrive already...

So...is a 458WM+ a gun whose magazine has been altered to take the longer COAL, or is it something else?

Lengthing the magazine of a M70 is relatively simple. Remove the magazine block and a 375 H&H mag follower

Is doing that what makes it a 458WM+? I assume you meant 375 bolt stop?

If you have a 458Lott, will reaming it with a 458WM reamer improve it, to regain that throat?

If you have a Lott with the WM throat, is there any downside to the Lott then?

My only thought about the Lott is that if you were hunting abroad, and needed ammo, you could choose between WM or Lott, whichever might be available.

You have to lengthen the magazine as well as the stop. Seat the bullet out of the case to increase powder capacity

If you put the 458 Win mag throat in the Lott you have what the original 458 Lott was before Iit was SAAMI'ed

Lengthening the throat is a relatively easy job for a GS. There are throating reamers easily available that will work.

Although not a 458, I had the throat lengthened on a 300 Win Mag Browning bolt, and used 375 H&H length mags to increase MV. Worked well though I wouldn’t do it again because choosing the right newer powders will enhance performance. The 458 Win Mag is a prime example of this approach.

So remove the magazine block, add a 375 follower and 375 bolt stop and you have a WM+. Correct?

Yes, but the issue is, is there a downside? Seems to me that a Jack Lott Lott would be very desirable since you could shoot WM or Lott in a pinch, and normally just load WM to whatever length and power you wanted. A SAAMI Lott, otoh, is obviously not as good.

I think I found my answer in that huge 458 thread, Sir Ron's Old Fugly seems to be and do exactly what I'm talking about.

Even IF the Lott is given the long throat of the .458 Win, it is still limited by the action length. For example: My CZ 550 in .458 Win had the full length Mauser action that allowed a COL of up to 3.78" (as a .458 Win Mag). The Lott version of the same rifle was limited to 3.6" due to it's relatively short throat as per SAAMI. In using a reamer to give it a throat like the .458 Win, it still would have been limited to 3.78" COL due to the action length - so in the end of matters, it would be no better than the "unimproved" CZ 550 chambered for the .458 Win Mag that I'd owned. Same for a Ruger #1 (which I now have) in .458 Win. I can seat bullets as long as the bullet itself permits depending on its OL.

Factory loads for each will give an advantage to the Lott due to an advantage in SAAMI psi for the Lott (62,500) vs the Win Mag (60,000 psi) which Sir Ron has pointed out multiple times, and due to the longer factory COL of the Lott. But I've never used factory ammo in any of my previous two .458 Win Mags, nor in my current Ruger No.1H. I had the option of choosing the Lott over the Win when I purchased the CZ 550, but chose the .458 Win without any regrets.

Bob
www.bigbores.ca

The .458 WM+ is not a rifle, it is a handload.
However it is not wrong to refer to your rifle as a .458 WM+ rifle.
That is a sign of enlightened joy.

A .458 WinMag handload becomes a .458 WM+ handload if COL is 3.350" or greater,
whether pressure is more or less than 60,000 psi.
Also, a .458 WM+ handload may be one with a COL of less than 3.340 if pressure is above 60,000 psi.
The standard SAAMI-chambered .458 WinMag is capable of firing .458 WM+ handloads,
and may produce higher velocity and lower pressure than the SAAMI .458 Lott with same bullet and barrel specifics.

Fit your .458 WM+ loads to your .458 WinMag rifle however you like,
whether long-magazine or short-magazine repeater, or single-loader.
There are many SAAMI-limited loads for the .458 WinMag that will push a 500-grain bullet at 2200 fps and more.
More than enough.
Propaganda be damned.

SLGPT, welcome to the forum, you can also do ALL that needs doing at 3.340" COL in the 458 WM, i bumped to the top a post i done early this summer with Browning 458 WM at 3.340 inch and 500gr partitions. it's in the 458 Win Mag thread, good luck and have fun, it's a great cartridge.

SLGPT,

Join the Square Table, pick a Sir Name , become a Knight of the Four Five Eight, please.
Sir Jerry has been doing great things with his FN Mauser and M70 Classic.
There is much more to come.