Does anyone have any experience loading for this calibre? I would appreciate it if I could get some idea of start loads, etc.

Thx

Glenn Bevin

Glenn, you need to let us know which 300 Mag case this gun is based on.

If it is a 6.5 X 300 Win Mag I do, indeed have some loading data for it. With light bullets it was faster than hell, but with 140,s it was hardly better than a good 264 Winchester Magnum.

R F

I have an interest in this cartridge as well, How fast and what powder bullet combo's were you using? I would love to hear any info you have on this one.

R. Flowers

This is a 300 Win Mag case necked down to 6.5. Any help would be greatly appreciated.

Thx

Glenn Bevin

Sounds to me like a 6.5 Mashburn Mag. Give a look into PO's book.

I've been using the 7 Mashburn Super for some time. (300 Win down to 7)

"GET TO THE HILL"

Dog

Well guys, I really had to search through my data to find this but I will list some loads that we tested in a 6.5 X 300 Win Mag. I am not claiming these loads are safe and if you use them you are on your own.

The rifle was built on a Ruger 77 action and had a 27 inch Douglas barrel.

Using W-W cases/CCI 250 primers/ 130 Barnes bullets:

78 grains IMR 4831 gave 3604 fps
79 grains IMR 7828 gave 3595 fps

We went even higher on the powder charges, but I am hesitant to list those loads here. Even the above loads extracted easily, but opened the primer pockets noticeably.

Using W-W cases/ Federal 215 / Speer 140 spitzer:

74 grains IMR 7828 gave 3429 fps
69 grains MR 3100 gave 3293 fps

The following loads are probably safer in my estimation. I used to get talked into chronographing all sorts of stuff for guys.

R-P cases/ Federal 215 /Sierra 140 BT

68 grains MR 3100 gave 3227 fps
69 grains MR 3100 gave 3287 fps
68 grains H 4831 gave 3246 fps
69 grains H 4831 gave 3317 fps
67 grains H 4350 gave 3293 fps

I guess that thing was faster than I remembered.
Keep in mind it had a 27 inch barrel.

These are probably all pretty darned hot loads. I would recommend starting well below them.

Actually, the 300 Win Mag makes a better basis for wildcatting than most people would believe. I also tested a couple of 7mm X 300 Win Mag rifles that were impressive.

Again, start well below these loads and watch for pressure signs. We really got fooled on the 130 grain loads. We thought they were perfectly safe until we tried to reload the cases and the primers would just about fall out of the case.

And when working with loads that might already have loose primer pockets, for Christ's sake do not try to pull any of them with a kinetic bullet puller. I did with some of these and that primer was jumping up and down in the pocket I guess, it went off anyway. It scared hell out of me. The powder did not ignite, but the primer dissapeared into the ceiling of my garage.

Have fun, R F

R F

Thanks for the info. Will update you after some extensive testing.

Glenn Bevin