Reloading 300 Win Mag

[EE_Reloader]

Hello everyone. I have been reloading for about 3 years now and recently found myself wanting to reload for 300 Win Mag. I have never reloaded a magnum caliber before so I set about learning as much as possible about the process. In doing so I stumbled across the "belt bulge" phenomenon. I must admit that this information has made me somewhat nervous to start this process. So I wanted to ask more experienced reloaders about their experiences. Is the "belt bulge" as big of a deal as I have read or will bumping the case .001-.002" using a FL Redding S die prevent this from happening? Has anyone ran into this problem and made your brass unusable? Any advice is appreciated. Thanks.

 

[DoneNOut]

Been using RCBS dies on my 300 WM no problem.

 

[ThrdKllr]

I've not had any problems with belted magnums. Some chambers can be a little long base to shoulder and trying to bump the shoulder.001-.002 may cause some of the reported problems. But there is a remedy.

 

[Mallardhammer]

I've never ran into it reloading 7 mag, 300wm, 375 H&H, and several weatherby cases. Not saying it doesn't exist and I'm sure I'll see it someday, but I've never had an issue with the area just above the belt while using standard FL dies to bump the shoulder.

 

[smokey3]

Graf and Sons sells the Peterson 300 WM Long brass, this will cure that problem before you run into it. Go to Peterson's website and Ben Peterson explains all you need to know about this version and remember they manufacture both long and standard versions and both are available on Graf's website. I have the long version from them and it is great brass. With that being said, I have reloaded 7 MM and 300 WM for years and have never had any issues with either one. Watch your pressure signs and do not overwork the brass and you should be fine.

 

[ShtrRdy]

The belted magnum case was designed to headspace off the belt. This was done because the original cartridge was the 375 H&H Magnum. It had very little shoulder to work with.

Since the 300 Win Mag has a nice shoulder it's a very good idea to only push the shoulder back as much as needed. Don't push it as far back as many sizing dies will allow you to do. By doing this we can avoid the dreaded case head separation problem.

The other problem that tends to develop is what I think you're asking about, is the case having a bulge just above the belt. This can be remedied by using the Willis Belted Magnum Collet die. It doesn't have to be done every time you resize a belted magnum, but rather after several resizing cycles.

 

[ThrdKllr]

Graf and Sons sells the Peterson 300 WM Long brass, this will cure that problem before you run into it. Go to Peterson's website and Ben Peterson explains all you need to know about this version and remember they manufacture both long and standard versions and both are available on Graf's website. I have the long version from them and it is great brass. With that being said, I have reloaded 7 MM and 300 WM for years and have never had any issues with either one. Watch your pressure signs and do not overwork the brass and you should be fine.

I'm using the Peterson Long brass also. Great stuff and a novel idea to make brass that fits the chamber on the first firing. I used to reform 300 brass for my 7mmRM to eliminate the stretch.

 

[smokey3]

The belted magnum case was designed to headspace off the belt. This was done because the original cartridge was the 375 H&H Magnum. It had very little shoulder to work with.

Since the 300 Win Mag has a nice shoulder it's a very good idea to only push the shoulder back as much as needed. Don't push it as far back as many sizing dies will allow you to do. By doing this we can avoid the dreaded case head separation problem.

The other problem that tends to develop is what I think you're asking about, is the case having a bulge just above the belt. This can be remedied by using the Willis Belted Magnum Collet die. It doesn't have to be done every time you resize a belted magnum, but rather after several resizing cycles.

I have the Willis Collet die just in case, but so far have not needed it. Great to have and since I have a 6.5x300 Weatherby I just might have to use it someday because that brass is expensive and hard to find sometimes.

 

[smokey3]

I'm using the Peterson Long brass also. Great stuff and a novel idea to make brass that fits the chamber on the first firing. I used to reform 300 brass for my 7mmRM to eliminate the stretch.

My ES dropped from 15 fps to 9 fps and SD from 9 fps to 4.6 fps using the Long brass and that was on initial loadings. I have not done a second loading yet, waiting to fire form all 100 cases first. I asked Ben if they were going to make the Long version for the 7 MM and he said no plans for that at the moment, hopefully they change their minds someday.

 

[ThrdKllr]

I shot a couple of 1 hole groups with the same load during my work up. Still in the process of developing a load for it.

 

[EE_Reloader]

Thanks for the information everyone. Might look into getting a Willis collet die, just in case I do have a problem in the near future. What powder is everyone using? I have some H4350 and IMR4831 that I am thinking of using. Curious what everyone thinks of these two powders for 300 WM.

 

[ShtrRdy]

It seems the favorite powder is H1000 or RL26.

 

[Steve L]

I'll second the H1000.

 

[ThrdKllr]

I'm working on a load with h4350 with Sierra 150 GK and Fed 210M primers (getting low on magnum primers). Let you know what I come up with. My rifle is very accurate with imr 4350 and 150 NBT.