I recently acquired a pre-64 Model 70 300 Win Mag. My son, a husky 21 yr. old, seems to have laid claim to it already, and enjoys??? shooting it lots!!!! So I guess I will have to start reloading for it sooner than I thought. I have been reloading for years, but only standard cartridges, like the '06, 270, 243, etc. And a bunch of pistol cartridges also. But this will be my first belted magnum. I have, of course, studied most of the manuals, and Waters' Pet Loads, but a few things bother me.......Like not setting the shoulder back during resizing, which primers to use,(some say only magnum primers), and how can I keep the bullets in place in that short neck? Any advice will be put to good use.. Thanks, Grant.

If the brass has been used in this rifle, neck-size it only.

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Neck tension is all that is required to keep the bullets in place (or at least that is all that is required on mine).

I have been reloading for the 300 win for years,
I have never had a problem with the short neck
holding bullets of any type includeing Nosler BT.
And if your just useing it for hunting FL size.

I happen to have the same unit as yours, truly a wonderful rifle that will see a lot of action. I find no problem with the short neck, especially with the 180 gr Partition PP. Loaded with 77.2 gr 7828 and Wim Mag primwers gives 3050 f/s and 1" groups. These are rare units and you are lucky to have one.

BR

That's a really nice rifle. Much better than what is made today and it should be shot and hunted like you are doing and not collected.

I check the insides of fired cases with a feeler wire that has a tiny hook bent onto it. If you feel a ring inside the case and it feels significant then saw that case in half. From the actual appearance you can decide how far to go on case life. I get quite a few reloads on that round as it has a good shoulder.

I use 180 gr bullets, imr 4350 and magnum primers and it shoots into 1 MOA. I have never tried other loads as that is plenty good for me. But that cartridge has been a target winner for years now at long range so it has potential.

I would buy a three die set for reloading so that if you neck size you can size all the way to the shoulder. Partial neck sizing with a FL die may not leave enough neck sized.

Tell us how it shoots.

Your belted .300 is really no different from a rimless case. Set your dies to headspace on the shoulder, just like you would with a .270, .243, etc. While the neck is shorter than usual, it will give you adequate tension.

Manufacturers have become increasingly sloppy in chambering belted magnum barrels, assuming that they will safely headspace on the belt (which they will), but leaving an enormous amount of play in the overall chamber. One reason they do this is that they can start with a chambering reamer which is somewhat oversize, thus they get more chambers out of it before it wears down below minimum spec. Fortunately, this is a problem you likely won't have in a rifle the quality of your pre-64 Winchester.

Use 180's and Reloader 22. Can't think of a better combo. set your dies for a full length resize, and backoff 1/4 to 1/2 a turn. This will set you up fine for just neck sizing them.

I've got one built on a 1903 high SN, and it shoots .75 3 shots. Since it's a rechamber, the barrels' too light for 5 shot groups in any meaningful time.

jeffe

I recommend the 180gr. Nosler Partition Protected Point bullets... they are made specifically for the short necked .300 Win Mag. They can be loaded out a bit more than the regular 180's thereby providing more powder room.