The are several opinions on the length of a 458Lott chamber. Please help me decide what to ask for when I have mine reamed out, weak area for me.. Thanks Marc

MADDOG:
I hope my memory is correct. I knew James Watts and wrote his memories is a small book. The original Watts round was 2.850 inches. About 22 years later, Lott shaved off .05 so he could have his name on something. Basically he took James' idea from 1948 or 9 and got the credit. I think 2.8 for the Lott is correct. The Watts chamber will take both the Watts and Lott as well as the .458 Winchester.
Hope this helps and my memory is sound.
Cal

I have a drawing on my desk from G. Sittons May-June 1991 issue of Handloader Magazine. Case length is given as 2.80", 71.12mm.

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Thanks to both of you. Am I wrong in thinking that one would go the 2.85 and have THR best of all three worlds??
And is there any long term damage in using the 458 win mag in the longer chamber? Thank you for the education
Marc

Hey Marc, don't forget to look at the .450 Ackley as well. I prefer it to the Lott and find the velocity can be greater without the added pressure. I am sure the Watts is on the same level.
Frank

MADDOG:
After I wrote the book on Jim Watts, he sold me the first .450 Watts he made up. For many years he, and later I, fired countless .458 rounds in it with no problems as to accuracy, throat erosion, etc... I regret selling the rifle but did so as double rifles are my passion.
If your choice is the Ackley round you can only use it as it has a very slight shoulder. The Watts and Lott will fire from in it but not the other way around.
Cheers,
Cal

It seems most logical to go Watts, 2.85" straight tapered round.

Wow.. Thanks to all of you guys. I really have been educated. I love AR
Hey Frank you be in my area soon? lets have lunch.. Haven't seen ya in a while... Marc

I had a CZ 550 .458 WM reamed out as it didn't feed the short WM rounds worth a darn. I took it home and tried to cycle hornady .458 lott factory through it. Couldn't close the bolt fully as the chamber was too sort with the bullet configuration. Took the round and rifle back and cut it to fit the round. Apparently there is some variance in chamber lengths? He said he cut it to specs.
Just an FYI

Now it cyles and shoots great

Per Jack Lott in the 10th edition of Handloaders Digest.....The 458-Plus Arrives....."I recalled the almost forgotten 450 Watts, the 2.850-inch belted straight tapered progenitor of the 458 Win Mag. It was based on the now unavailable Norma H&H belted cylindrical basic brass which made a 458 caliber straight tapered case. I was uninterested in resurrecting the Watts, and a full length 375 H&H case shortens to under 2.850 when necked up to 458........By trial and error, I settled on 2.800 inch case length, just 3/10 inch longer than the 458 Win Mag case. I drew up a case and reamer design with minimal mouth diameter and a short " forcing cone "to preclude excessive misalignment of bullets fired from 458 cases in the long chamber.My measurements established that when the base of the 500 grain bullet leaves the case mouth, the forward portion of the cylindrical base section behind the cannelure is already .260 inch into the barrel and obturating.

Sledge:
Or, a more simple explanation, one that Jim Watts told me, was that Lott simply shaved off .05" to put his name on a case that did the same thing Jim did 22 years earlier (in 1948-9). Watts was the innovator. Lott could not go longer as such as parent case did not exist and to keep the same length would also mean keeping the .450 Watts name, so it was easy to cut a bit from the length but not too much so MV and ME did not take a loss. And, Lott was now able to put his name on something that Watts did.
Just thought I'd mention it.
Cheers,
Cal

Thanks Cal, appreciate your input.

quote:

Originally posted by MADDOG:
The are several opinions on the length of a 458Lott chamber. Please help me decide what to ask for when I have mine reamed out, weak area for me.. Thanks Marc

Marc,

The CIP/SAAMI specifications for the 458 Lott are a 2.800” maximum case length and a 2.8098” minimum length to neck chamfer (chamber). For the 458 Watts you’re looking at 2.850” maximum case length and a 2.8598” minimum length to neck chamfer (chamber).

What you’ve not stated is the action that you’re using. Does the internal magazine length of the action allow the 2.85” Watts case when loaded with a long-heavy DG bullet using a standard shank seating depth to reliably feed from the magazine or will you have to seat the bullet deeper within the case for fit and feeding requirements? If seated deeper do you gain anything over the 2.80” Lott case? The answer to these two questions will answer whether your cartridge will be the 458 Lott or the 458 Watts.

Hello Capoward.
I am going to convert my 458 win mag model 70 " classic safari express"
I am not sure what mods will be needed to carry the new Lott round.
Marc

Your limiting factor on over all case length may be magazine length. On the the Pre-64's, it wasn't long enough for the 2.850" case if you wanted to seat most 500 grain bullets in the cannalures. I suggest to check that out.

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