Tips for reloading 300 Win Mag

[jlamb]

I have just bought a Ruger Mark II 300 Win Mag and I am getting ready to load some cartriges. I have seen some info about headspacing on shoulder vs belt that sounded complicated. I am using new Remington brass. Also, the recipes I'm looking at calls for LR primers vs LR Magnum primers. Any thoughts?

I am going to start with a 165gr Hornaday SST bullet and probably 69gr of H4350 powder.

 

[strambo]

I've had better luck accuracy wise with LR primers. Magnum primers would be better for hunting loads, especially in cold weather to ensure good ignition.

In general, I'd start with heavier bullet weights. 180-220 grains is a good working range for 300WM. My rifle likes 200s best. Sierra 200 SPBT bullets are on sale in the latest catalog from Midway right now for $5 per 100!

 

[dakotasin]

magnum primers and rl-22... about all you need to know for stuffing 300 win mag cases.

don't worry about the belt vs shoulder thing. once-fired brass will neck size just fine, and if you stay off the shoulder when re-sizing, you'll have your headspace on the shoulder like any other case.

 

[flashhole]

I'll second the opinion regarding heavier bullets for the 300 Win Mag. My favorite bullets are in the 200 grain family, usually Speer and Sierra. I won't go lighter than 180 grain bullets for this cartridge. I like Retumbo powder and Winchester Large Rifle Magnum Primers. Magnum primers are hotter than conventional primers. Not a different compound, just more of it. Large powder capacity cartridges generally call for slow burning powders and many load manuals will specifically call out a magnum primer to enhance the ignition process. Uniforming the flash hole in the brass is something you can do to ensure it is fully open and provides uniform ignition.

Fit check the new brass to your gun before loading it. I had an experience with my 7mm Rem Mag where new brass wouldn't chamber properly. I discovered it after I had loaded 20 rounds. Now I make it a point to full length size all brass the first time they are to be used. Neck sizing after they are fire-formed to the chamber extends brass life and will also help in the accuracy department.

Be aware, when you read max load for a specific bullet it means max load. The obvious consideration is that going above max load is dangerous to you and the gun but the other, lesser considered reason is, bullet integrity is not the same for all bullets. Under too high a charge the bullet can break apart in flight.

 

[MNgoldenbear]

... Under too high a charge the bullet can break apart in flight.

Unless you're looking at very thin jacketed bullets, I don't think this is very likely in the velocity range of the .300 Win.

A note about load data, since the original post seemed to suggest swapping components in load data. Note that the load data was valid for the components and conditions used -- cases, bullets, powder, primer, chamber dimensions, temperature, etc (including the lot of the ammunition components). Any changes can alter the performance and safety of the load. Even if you use the "same" components, some of the variables will be different. If you change components, realize that you are working up a separate load using the load manual as a general guide. If you are working at or near maximum velocities for the components you are using, be careful -- increase charges gradually, watch for pressure signs, note temperature when testing (at least general range) -- all the basic stuff you normally should do. Handloading is a lot of fun, but less so if it earns you a nickname like "Stubby".

 

[USSR]

Like some of the posters said, start buying RL22 and heavier bullets.

Don