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Re: Same case, different caliber - is there a rule

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14 November 2004, 05:06
Clark
Re: Same case, different caliber - is there a rule
Quote:

Here is a reasonably good figure to use.



In the following bore sizes



270, 30, 338, 375, 416 and 458 the percentage change between each calibre is almost identical.



If you move down one calibre, such as 30 to 270 then the small calibre will use about the same load with a bullet that weighs 60% of the larger calibre. That is, top loads for a 110 grain 270 will be about the same as top loads for a 180 grain in 30 calibre, using the same case of course.



A 30/06 with 150 grain bullets would be similar to the 338/06 with 250 grainers and ditto for the 30/378 and 338/378.



Mike





Great pattern!

Why didn't you keep going with smaller bores?
12 November 2004, 05:35
vapodog
Quote:

can you load a case with the same charge in different calibers?



Please don't do this!!!

Consult a loading manual for each cartridge you load. Loading data is available free from IMR, Hodgdon, Alliant and others.
12 November 2004, 05:10
JustC
Bore dia has more to do with it than anything. The bigger the "piston" the faster the pressure drop as it moves foreward. This is illustrated by my pards 7mmRUM using 86gr H1000 with a 162gr to reach the pressures I have in a 300RUM with a 200gr pill and 88gr of H1000. His bore is smaller,..so he uses less powder (assuming same case design) to reach that same pressure. MHO,..I'm no balistician though.
13 November 2004, 09:38
Wstrnhuntr
Yes! There is a rule. Data among chamberings should be considered as NOT interchangable unless specifically stated as such.

And remember, bullet "weight" is one variable that effects pressure. A 30 caliber bullet and a 25 caliber bullet of the same SD are NOT going to weigh the same.

Other variables coming into play here as well that have already been pointed out.
12 November 2004, 04:57
Ol` Joe
Not that I`m aware of. Take the 30-06, 280, and 270 with similar SD bullets, 270 = 150, 280 = 160 and the 180gr in the `06. Useing H4831 you`ll see 5-6 gr differance in max powder charge. H4350 has a wide range also.