7MM 08 40' Improved

[Rocky Raab]

So-called "Improving" of rifle cases was a passably good idea when most rounds were long, skinny and sharply tapered. Improving the .25-35 worked wonders for it.

But all that abruptly changed when cases started coming from the factory with fat bodies, little taper and reasonable sharp shoulders. The 7-08 fits that description and is already "improved" just as it comes.

If you try to "improve" it even more, you run into possible feeding problems with very steep shoulders, you spend double or triple on loading dies and gain...well, let's examine that.

There's a long standing and very well proven formula that says you will gain or lose velocity by one fourth the percentage of case volume change. In this instance, a 7-08 case holds about 50 grains of water by weight (the usual standard). If you blow the case out and sharpen the shoulders as much as possible, you might be able to add four grains of water to that.

Now, 54 compared to 50 is an eight percent increase. One fourth of that is two percent. If your un-improved 7-08 got 2800 fps with a given bullet, then all your expensive dies, re-chamber job and fireforming of cases gains you an extra (drumroll here) 56 feet per second. That's about what you'd see in the variation between two shots of a UNmodified 7-08.

Worth it? Not to me.