264 win mag and 7mm rem mag

[jrw1976]

Ok Gentlemen I was reading my reloading manuals last night to relax and I was comparing the 264 win mag to the 7mm rem mag. What I was wondering about is why if the cases are virtually the same, why is the max loads 2-3 grains different (depending on the manual) using 140 grain bullets. I really do not get the logic behind these theories. Currently I am loading 69.5 grains of H1000 behind a 140 grain berger in my 7mm rem mag and 70 grains is max in the manual. But the book calls for the 264 win mag to have a max load of 68 grains of H1000 behind a 140 grain bullet. I don't understand why 2 cases of virtually the same dimensions and pushing the same weight bullet can be so different. I would really like someone smarter than I, to shine some light on this subject.


Thanks, Jason

 

[bassin93]

because of the smaller dia of the 264 yet being the same weight the 264 has to be longer, thus more bearing surface on the bore, smaller base area for the pressure to push against which runs the pressures higher. hope I explained that to you where it makes sense

 

[jrw1976]

Actually your explanation makes perfect sense. Now I know.

Thank you, Jason