Home Forums Hunting & Shooting Express Rifles and Big Bores Only The great 458 Winchester. Everyone should own one at least once

From the .450 Rigby thread:

Riflehunter said, in black, my comments in red:

If the standard .458 WM chamber is long-throated
... Yes, it is famously long throated as the standard SAAMI chambering ...
and modified
... only the ammunition is modified, to be precise, no modifications to the standard SAAMI chamber ...
so that it effectively becomes a magnum-length cartridge
... we call that the .458 WM+ "wildcatted ammunition" which is not limited to lower pressure and shorter length than the SAAMI .458 Lott ...
(so as to hold more powder and reach 2300 fps),
... we assume you are speaking of 500-grain bullet at 2300 fps, to be more specific ...
wouldn't it be better to have the case longer so that it fits the standard cannelure of the bullets that are now sticking out further, rather than cut a new cannelure further down the projectile?
... Take for example the 500-gr TSX that has 5 cannelures/grooves and is on average about 1.660" in length
(from lots of 1.650" to 1.670" lengths that I have measured)
which may be loaded to COLs of roughly 3.78", 3.68" or 3.58" using the 5th, 4th, and 3rd cannelures already there.
At 3.58" COL, the seating depth is 0.58", way more than enough.
To load the same bullet in the .458 Lott with 2.8" brass, one must use the first cannelure on the bullet
and trim the 2.8" brass down to 2.760", according to the Barnes manual, in order to make maximum COL loads for the .458 Lott.
With that, the seating depth in the Lott will be 0.820".
What a waste.
That is what happens when you make brass 0.3" longer and try to shoehorn it into a rifle action that allows only 0.2" longer magazine.
There has been a rash of shortening bullet noses that were formerly optimum for the .458 WinMag, so as to make them work more easily in the SAAMI .458 Lott.
Yes a rash broke out with the SAAMI .458 Lott disease ...
This would give more support and protection to the projectiles that are subject to violent recoil when in the magazine
True, but many .458 WM+ loads have more than enough seating depth and are locked in place by 100% load density
and a Lee Factory Crimp Die. They do not pull loose and they do not get battered deeper into the case ...
and would also give more support to very light short bullets that would otherwise have either a very long jump to the lands or have very little of the neck holding them.
... That is why I say that the SAAMI .458 Lott is only better with birdshot for snakes and rat bullets for small pests.
If you want to fix the SAAMI .458 Lott, then give it a throat like on the wildcat version that Jack Lott built.
The long jump with short bullets in the .458 WinMag is somehow not an accuracy impediment, it just works.
The short and tight throat in the SAAMI .458 Lott will not even allow cast bullets of proper diameter for best accuracy,
unless they have bore-rider noses and have the full diameter seated deeply ...

And continuing there, buy a donkey to Sir Meplat for the illustration:



That is exactly what I did with the Woodleigh data for the 400-gr PPSN in the .458 Lott.
I took the maximum load for the .458 Lott and loaded it to the 3.425" COL of the .458 Lott load (when crimped on the Woodleigh factory cannelure)
but in the .458 WinMag at same COL, using an added cannelure (not needed with Lee Factory Crimp Die).
I thus exceeded 2600 fps with the 400-grainer,
with same COL and same degree of powder compression as required in the .458 Lott,
with H4895.
The pressure of this .458 WM+ load fired in a SAAMI .458 Winchester Magnum chamber
must be lower than the pressure of same load in a SAAMI .458 Lott with short and tight throat.
Physics does not lie.