Apr 11, 2018

The 3" .458 Express Belted Magnum


Although I hear many in South Africa have converted their 458 Lott to the 3" .458 Express Belted Magnum (Several name for this exist), there is little to nothing available in this here in the USA. It is considered a Wildcat here.


Except. It appears I have one somehow. It does not say so on the barrel, yet it gulps down a 3.9" round without a qualm. Remember the Lott MAX COAL is 3.6". The 458 Express MAX Coal is 3.8". So I wonder on the history of my CZ 550, since I obtained it second hand with a bedded Kevlar stock.


The gun responds to loads like a 458 Express, and not like a Lott. The 3" Express offers significantly more volume, so can put out the same ballistics as the Lott with about 15% less pressure. Some think this fact reduces recoil, however you cannot fool Newton's Law. For every action, an equal and opposite reaction that is.


Less pressure is a good thing certainly. No shell binding, splitting, etc. If you want more power, then you can have it - because the pressure max remains 62,000 psi.


Personally, the Lott is powerful enough, and I plan only to take advantage of the reduced pressure on my upcoming hunt in May.

Apr 13, 2018

Thank you for that, Michael.


The .458 3" Express was developed by Prof Koos Badenhorst of the Engineering Faculty of the University of Pretoria to alleviate the one problem we have in SA with the Lott - over pressure during our warm days even in winter and the subsequent possibility of extraction propblem. S321 propellant is volume-wise the best powder but it is a distinctly temperature sensitive mix being double based.


S335 is totally ignorant of temperature but is quite voluminous and requires too much compression to get the required 2,200 ft/sec for proper wet stabilisation of a 500gr bullet. Local propellants just do not meet that perfect thermo dynamic niche available to the US reloader of the .458 calibre. The chemistry-unchallenged reloaders here have developed a secret duplex load of these two propellants and are quite happy with their Lotts - but of course you will never see this recipé in print.


The 103 gr water volume of the Lott asked to be increased and Prof. Badenhorst decided that 111 gr of water volume is enough. His idea was never to have a super Lott but to simply achieve the 2,200 ft/sec at much lower pressure but a lot more gas volume. Of course most reloaders will force the last pound of pressure already from their Lotts, and so do some 3" Express reloaders but is unnecessary.


Here are some of the good professor's own tables of results:


For 30-06 type game:

  • 350gr Impala monolithic brass: 90 gr S335, 2,670 ft/sec and identical 30-06 trajectory with 180 gr bullets.

  • 500gr Woodleigh: 95 gr S365 at 2,200 ft/sec. This was his favourite buffalo load.

Regarding the recoil issue: If one only sees recoil as the opposite reaction to the raw momentum value of the bullet as it leaves the muzzle, and relates that value rather simplistically to what the good sir Isaac Newton mentioned in his third law the assumption will be that a certain velocity will give a certain opposite and equal recoil. However - just as bullet penetration is based on impulse and not raw momentum, and because impulse is related to the rate of change in momentum, the bullet that starts out quite bit slower due to the quite a bit lower peak pressure, and accelerates slower to still reach the same muzzle pressure and muzzle velocity due to a longer push due to quite a lot more gas volume has a fair amount of lower impulse. The felt recoil, just as penetration is related to impulse and not momentum.


Exactly like my equation for penetration, recoil is a force - and Sir Isaac himself said that Force = Mass x Acceleration. The .458 3" Express has a 25% slower acceleration than the Lott, spread over a longer time. The rest of the arithmetic is easy.


I shall have three dummy 3" cartridges ready, lengthened with 500 gr bullets to the magazine length of a BRNO ZKK 602. If they feed into your chamber you have a clever rifle there.


Apr 13, 2018Edited: Apr 14, 2018

The load I am bringing to Africa was shot on a 70 degree day at sea level with 95% humidity. It consists of 83.3g RE15, 480g Peregrine VR2, COAL 3.606, Winchester WLRM primers and Hornady new brass. Fill is 104%. Velocity was 2238 fps at the muzzle. Zero is at 50 yards with a 1x4x24, 30 mm scope, using 1 power.


Note that QL predicts this to reach 2355 fps. However, like I said, this rifle is reacting like a 3" Express. With the same load in the Express and a 3.8" COAL, QL predicts 2276 fps. Since there remains freebore even with a COAL at 3.8, the actual velocity is 2238 fps. When I use the 3.9" max that the chamber will accept, the program predicts 2239 fps. Spooky, right? The pressure for this is way down at 44,142 psi.


For what you say the be true Andreis, your barrel would have to be 25% longer. It is the velocity of the bullet at the muzzle that counts, actually. QL has a feature that can tell you where it predicts all of the powder to be used up and burned, and can also show that the bullet continues to accelerate while in the barrel. The wave shape changes are from different powders and bullet weights.


ALL of the recoil calculators ask for the same thing. Weight of gun, weight of bullet, muzzle velocity and maybe diameter so they can make other calcs. They do NOT ask for barrel length or chamber size or powder type.


The more complex calculators ask for charge weight. Using this one, the recoil energy of the Lott is actually less than the Express because the express uses more powder for the same velocity. The momentum is the same.



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