A brass hoarding machinist buddy of mine suggested and offered to...
Mod 300WM and or 7mm mag brass for me to use in my 450.
He said he could turn down the belt and rim, and trim the case to length.
Have any of you tinkerers tried this?
Modding 300WM or 7mmmag brass
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Modding 300WM or 7mmmag brass
by mnhornet » Fri Jan 31, 2014 10:20 am
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mnhornet - Posts: 119
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Re: Modding 300WM or 7mmmag brass
by pitted bore » Mon Feb 03, 2014 11:39 pm
mnhornet-
I have no direct experience with your proposal for converting 7mmRM or 300WM brass to 450B brass.
However, I did consider it briefly some time ago, and decided against attempting it, because getting the case head formed properly might be a challenge. Here's a diagram that may help illustrate my explanation.
.
The drawing shows the head of a 7mmRM or 300WM case, with the dimensions of the belt and of the case just in front of the belt being given.
The principle problem in conversion of the 300WM case to 450B may be the 0.510" diameter of the Mag case just in front of the belt.
The head of the 450B case just in front of the extractor cut is 0.500" maximum, and 0.494" minimum. The belt of the Mag case can be readily turned to 0.500".
But what is to be done about the 0.510" diameter of the Mag case in front of the belt. You likely cannot simply turn it also to 0.500". The case wall at that location is not sufficiently thick to be reduced without seriously compromising the strength of the case. (This is also the place where most case stretching will take place, and may increase the possibility of case head separations.)
If only the belt is turned to 0.500, it results in a 0.010" step up in the case wall, placed just in front of the former location of the belt. Full length resizing might squeeze the case to 0.500" at that point, but it will produce a fold in the interior case wall.
To avoid the step, the belt could be turned to 0.510". The resizing die would then have the task of swaging the solid head to 0.500". I suspect this would be a real chore for the average reloading press, and may result in some distortion of the head; the brass has to go someplace.
It's quite possible I've over-looked some important part of the process, and I'll be pleased to be educated about it.
After the head is reformed properly, there remain the problems of loading for a LR primer, of a possible need for inside neck reaming, and of correcting powder charges for altered case capacity.
If you decide to go ahead with the project, a report on its success and some photos would be really helpful.
Good luck.
--Bob
I have no direct experience with your proposal for converting 7mmRM or 300WM brass to 450B brass.
However, I did consider it briefly some time ago, and decided against attempting it, because getting the case head formed properly might be a challenge. Here's a diagram that may help illustrate my explanation.
.
- Head of case of 300WM and 7mmRM.
- 300wm.png (5.42 KiB) Viewed 3640 times
The drawing shows the head of a 7mmRM or 300WM case, with the dimensions of the belt and of the case just in front of the belt being given.
The principle problem in conversion of the 300WM case to 450B may be the 0.510" diameter of the Mag case just in front of the belt.
The head of the 450B case just in front of the extractor cut is 0.500" maximum, and 0.494" minimum. The belt of the Mag case can be readily turned to 0.500".
But what is to be done about the 0.510" diameter of the Mag case in front of the belt. You likely cannot simply turn it also to 0.500". The case wall at that location is not sufficiently thick to be reduced without seriously compromising the strength of the case. (This is also the place where most case stretching will take place, and may increase the possibility of case head separations.)
If only the belt is turned to 0.500, it results in a 0.010" step up in the case wall, placed just in front of the former location of the belt. Full length resizing might squeeze the case to 0.500" at that point, but it will produce a fold in the interior case wall.
To avoid the step, the belt could be turned to 0.510". The resizing die would then have the task of swaging the solid head to 0.500". I suspect this would be a real chore for the average reloading press, and may result in some distortion of the head; the brass has to go someplace.
It's quite possible I've over-looked some important part of the process, and I'll be pleased to be educated about it.
After the head is reformed properly, there remain the problems of loading for a LR primer, of a possible need for inside neck reaming, and of correcting powder charges for altered case capacity.
If you decide to go ahead with the project, a report on its success and some photos would be really helpful.
Good luck.
--Bob
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pitted bore - Posts: 700
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