Gents:

Could someone explain this concept to me? I believe there are various magazine box geometries out there, correct? For instance, I have read that D'Arcy Echols has his own as may a few others. I have also read a few makers of actions create the magazine to fit the specific cartridge. What are the differences/similarities/justifications?

Could someone use a the Model 70 Classic as an example to explain?

Thanks.

The M70 classic is a bad example due to USRAC using a one size fits all approach. All of the Long action M70's used the same box be it a .270 or .30-06, short belted mag or long belted mag. They accomplished this by tacking a filler block in the back of the mag box for the standard and short mags. This is why Echols manufactures boxes of his own design for his M70 classic conversions.

The pre-64 m70's in .30-06, .270. and the H&H mags are a better example. Both had mag boxes designed for the exact cartidge ( or cartridge family). This is why the pre-64 H&H mags hold four down and feed very, very well for a factory rifle. The feed rails and follower have much to do withthis as well as the entire system needs to work together in a CRF rifle.

This by the way is all taken from the Mauser 98 design/system. IIRC Mauser had somthing on the order of 20-30 specific mag box specifications to accomodate different cartridges in the M98.

Mausers formula to calculate magazine box width is:

(cartridge base diameter x Cosin30)+ base diameter

(Use shoulder diameter for the shoulder calculation.)

The Mauser calculation works very well. However I have a simple approach taught to me 40 yrs ago by my first Gunsmith mentor. Take three cartridges and hold them together with a rubber band, take the base and shoulder and bullet length dimensions. Make your box .030 over in all dimensions. I've used this trick and taught it to others and its worked flawlessly over the years on many guns where I've had to make a box.-rob