460 Short A-Square Conversion Project

[PolymathPioneer]

I am preparing to have a classic Winchester M-70 in 458 win mag converted to 460 Short A-Square. Originally I was considering conversion to the 458 Lott but didn't feel comfortable with the result due to several issues that I previously discussed on THR in a couple of different threads. The net of the project is: instead of a risky "minimalistic" 458 Lott conversion (no mag box re-build etc) I am going for an "extensive" 460 Short A-Square conversion, (I understand brass is an issue etc). The 460 Short A-Square is a very accurate necked down version of the 460 Weatherby Magnum. Hand loading the 460 Short is very flexible, it shoots flat and has demonstrated to outperform 460 weatherby magnum 500 grain rounds at a consistent, easily achieved, lower velocity of 2400 FPS. The project requires at a minimum: re-bedding of the barreled action, reinforcing the stock, re-manufacturing the magazine box (and other aspects of feeding), re-doing the ejection port in addition to rechambering the barrel and opening the bolt face. Before I have the work done by a competent gunsmith, (I am in the process of selecting), I want THR to way in on other conversion issues I might consider for this 460 Short A-Square M-70 project. Note: I am experienced in the use and recoil of big bore rifles, i.e. 375 H&H and up. This rifle is for African dangerous game during next seasons hunt, this rifle will not have a muzzle break. Finally, my experience with a CZ 458 lott is it doesn't shoot near as flat out to 250 yards as the 460 Weatherby (one of my reasons for the 460 Short). If others have experience otherwise (this means H&H and Loosedhorse) I am very interested to hear your experiences.

Postscript: I am bringing one rifle on this hunt for myself, i.e. the 460 Short will handle both short range Buff and longer range Kudu. I love my 375 H&H (it can do it all) as well as my custom 458 win mag bush rifle, but want to try something different for this hunt. My wife will be bringing her CZ 458 Lott on this hunt, (as she always does).

 

[56hawk]

Sounds like you have everything covered. Any idea on how the magazine conversion will go? My 460 Weatherby magazine is a lot different than my Winchester Model 70. The rounds go in more like a single stack pistol magazine. They might pop out of the Winchester magazine if the bolt is worked hard. Don't know, just something to think about.

The only other thing is about slower bullets outperforming faster bullets. I actually saw an article claiming that a 45-70 would outperform a 458 Win Mag. My understanding is that the bullet needs to be matched to the velocity. A higher velocity bullet will outperform a slower bullet as long as it's not being pushed beyond it's design limits causing it to fragment or tumble. Anyway, not really related to your build just felt like mentioning it.

 

[PolymathPioneer]

Sounds like you have everything covered. Any idea on how the magazine conversion will go? My 460 Weatherby magazine is a lot different than my Winchester Model 70. The rounds go in more like a single stack pistol magazine. They might pop out of the Winchester magazine if the bolt is worked hard. Don't know, just something to think about.

The only other thing is about slower bullets outperforming faster bullets. I actually saw an article claiming that a 45-70 would outperform a 458 Win Mag. My understanding is that the bullet needs to be matched to the velocity. A higher velocity bullet will outperform a slower bullet as long as it's not being pushed beyond it's design limits causing it to fragment or tumble. Anyway, not really related to your build just felt like mentioning it.

The magazine re-build is my major concern and is the determining factor in the selection of the gunsmith for the conversion. I saw that material on the 45-70 versus the 458 win mag too but I believe it was refuted on the same forum or at least it was pointed out it was not an apples to apples comparison. On the 460 Weatherby I had a Mark V that I put about 200 rounds through (total with muzzle break from a bench and without the break offhand). It was extremely accurate and flat shooting (out to 300 yards), however its a very big rifle. With the scope it weighed in at about 13 lbs if I remember. I sold it in favor of CRF rifles, which I have stayed with ever since. The bluing on the barrel changed color at about 150 rounds, (half way down the barrel), with factory pressures although the ambient temperature was about 110 degrees. I should have sent it back to Weatherby under warranty but just sold it.

 

[56hawk]

On the 460 Weatherby I had a Mark V that I put about 200 rounds through (total with muzzle break from a bench and without the break offhand). It was extremely accurate and flat shooting (out to 300 yards), however its a very big rifle. With the scope it weighed in at about 13 lbs if I remember. I sold it in favor of CRF rifles, which I have stayed with ever since.

That's pretty heavy. Mine only weighs 9.5 lbs. No scope though, and it's a pretty old rifle with the magna porting instead of the removable break.

The bluing on the barrel changed color at about 150 rounds, (half way down the barrel), with factory pressures although the ambient temperature was about 110 degrees. I should have sent it back to Weatherby under warranty but just sold it.

I've only put 100 rounds through mine. The guy I bought it from said it had only been shot twice, and it looks like it too. Hope it holds up.

Anyway, good luck with your build, and keep us informed on how it goes.