Resizing belted magnum cases, in particular, .300 H & H Magnum.

[David LaPell]

I recently found a Remington 700 Classic in one of those calibers I've long admired, a friend of mine was once big on it for hunting everything from deer on up, and that's the .300 H & H Magnum. I've heard though that resizing a belted magnum case is different than a normal rifle case, how so and what do I need to look for? I don't plan on loading this round too hot, thinking 165 grain bullet and lighter or moderate charges.

[sharps4590]

My oldest son has been shooting a Mod. 70 in 300 H&H since I bought it for his high school graduation in 1991. He's never found anything different. I shot the 300 Win. Mag for about 2 decades, the 264 Win. Mag and a 375 H&H Mag and I never had to do anything different because of belted cases.

[MUSTANG]

I recently found a Remington 700 Classic in one of those calibers I've long admired, a friend of mine was once big on it for hunting everything from deer on up, and that's the .300 H & H Magnum. I've heard though that resizing a belted magnum case is different than a normal rifle case, how so and what do I need to look for? I don't plan on loading this round too hot, thinking 165 grain bullet and lighter or moderate charges.

I have a Remington 700 Long Range in 300 WinMag. I had collected brass for the 300 WinMag from range pickups over a few years before I bought the 700 WinMag. Reloading the brass I found a % would not chamber; did some research and found discussions on the "Case Bulge Problem" just above the belt on these cases. I did more research and found the Belted Magnum Collet Resizing Die from Reloading Technologies (https://www.larrywillis.com).

The Collet Die

284211

removed the bulges and I found I infrequently encountered chambering problems after I started using it. I full Length resize cases, use the Collet Die to remove any potential bulge, check for chambering in a Lyman Brass Case Checker, trim to length, reload the brass, and check the final loaded round in the Lyman Case checker one last time to ensure it will chamber. Although it takes additional steps for reloading the Belted Magnum 300 WinMag using the Collet Die; it has dramatically reduced chambering problems with the brass/reloads for my Remington 700 Long Range in 300 WinMag.

[racepres]

Said it before.. All my acquaintances reload for their one in particular rifle, and so, all have done like me, and resize necks only. Using a carbide 32ACP die.. Only "chambering problems" have come from that "One Guy", who loads just a bit Hot...
Not for Everyone... But, works for some of us.

[GregLaROCHE]

I never used anything but a normal resizing die for my 7mm rem mag that was belted. Also I’ve heard that the very bottom of any case never gets resized.

[too many things]

you wont have problem if the cases are from same gun if not you may have to grind the face of the size die so the case will go ALL the way up.
the dies have a rim and the shell holder will leave about 1/8 space at the belt . try to use brass from same gun
had problems with 7mm mag
there is another option if you can find on the bay is the old "sleeve" die it has changeable inserts and will do it fine

[Minerat]

I have salvaged probably 100 7mm Rem mag cases using the tool Mustang shows. I use it in my 300 wby too. My 7mm cases start to get hard to chamber after the 3rd reload. I load to mag factory velocities or a tad over but not near max. I get 2 more out if the before getting split necks. I don't anneal or I might get more.

[AZ Pete]

size the same as any bottle neck ctg. The belted mags were designed to head space on the belt rather than the shoulder of the case. You will get much better case life by head spacing on the shoulder.

[SoonerEd]

I have a Remington 700 Long Range in 300 WinMag. I had collected brass for the 300 WinMag from range pickups over a few years before I bought the 700 WinMag. Reloading the brass I found a % would not chamber; did some research and found discussions on the "Case Bulge Problem" just above the belt on these cases. I did more research and found the Belted Magnum Collet Resizing Die from Reloading Technologies (https://www.larrywillis.com).

The Collet Die

284211

removed the bulges and I found I infrequently encountered chambering problems after I started using it. I full Length resize cases, use the Collet Die to remove any potential bulge, check for chambering in a Lyman Brass Case Checker, trim to length, reload the brass, and check the final loaded round in the Lyman Case checker one last time to ensure it will chamber. Although it takes additional steps for reloading the Belted Magnum 300 WinMag using the Collet Die; it has dramatically reduced chambering problems with the brass/reloads for my Remington 700 Long Range in 300 WinMag.

This is what I use and it works well. Sizes down to the belt so no bulge.

[Landy88]

size the same as any bottle neck ctg. The belted mags were designed to head space on the belt rather than the shoulder of the case. You will get much better case life by head spacing on the shoulder.

^^This.^^

Full length resize only for new brass or brass from a different rifle, after size for slight resistance on bolt closure. Full length resizing every time cases begin to fail after as few as four loads. AZ Pete's technique will give case life to equal any other case at similar pressure and improved accuracy. I learned, long ago, the hard way, as a kid that could ill afford for his cases to crap out so soon from constant full length resizing.

[David LaPell]

size the same as any bottle neck ctg. The belted mags were designed to head space on the belt rather than the shoulder of the case. You will get much better case life by head spacing on the shoulder.

The only problem with is that I read in a couple different reloading manuals that because the .300 H & H Mag & .375 H & H don't have that sharp of a shoulder like later magnum rounds, they HAVE to be headspaced on the belt and not the shoulder. If I headspace on the shoulder on the case when it tells me to headspace on the belt, will it wear out the cases faster?

[AZ Pete]

you can head space on the shoulder. It just takes a little more care with the 300 H&H and 375 H&H. It will give you the best chance for good case life vs head spacing on the belt.

[country gent]

One pf the hardest to set dies to correctly bump the shoulder for is the 22 hornet do to the body taper and gradual shoulder, But a good case gauge makes it much easier.

I have a Ruger Number 1 B in 300 win mag and size to just bump the shoulder back .002-.003 from fired cases. Sizing the case in this manner gives a good fit and best case life for me. Setting the sizing die to touch shell holder may push the shoulder back up to .010 or a little more working the brass much more both firing and sizing and shortening case life. I do lightly anneal cases for this also.

The above shown die would give the best of both sizing the case clear down to belt and allowing shoulder to just be bumped back.

[Minerat]

That Larry Willis collet die only resizes the immediate area above the belt, it does nothing to the shoulder or neck.

[Mk42gunner]

The only problem with is that I read in a couple different reloading manuals that because the .300 H & H Mag & .375 H & H don't have that sharp of a shoulder like later magnum rounds, they HAVE to be headspaced on the belt and not the shoulder. If I headspace on the shoulder on the case when it tells me to headspace on the belt, will it wear out the cases faster?
Actually headspacing on the shoulder instead of the belt will work the cases less. If you do move the shoulder back a few thousandths too far, the belt is still there to provide a safe headspace.

I would try it with normal dies first. If things work okay, no need to buy the extra collet body die. If you do need it after trying, then buy the extra die.

Robert

[243winxb]

What shoulder? Lol. 300 H&H

If one would study the SAAMI chamber headspace specifications, it shows a possible tolerance of .015" maximum. Slop in a loose chamber.

When head clearence is set by using a long head to shoulder measurement , minimul shoulder bump, THE AREA IN FRONT OF THE BELT BECOMES UNSUPPORTED. The brass will bulge after a few firings. The round will no longer chamber. Now you need the Willis tool.

[243winxb]

The 300 win mag has a nice shoulder.

[Minerat]

243winxb. You just hit it out of the park. If you headspace a belted case on the neck the case bulges above the belt an the cartridge will not seat in the chamber. A 300 Wby has a very well defined shoulder but it still bulges even with neck sizing, not as bad as the 7mm rem mag but still they eventually will not chamber. I full length size and use the collet each time, because my rifles are used for hunting and a sticky case is not acceptable.

[AZ Pete]

What shoulder? Lol. 300 H&H

If one would study the SAAMI chamber headspace specifications, it shows a possible tolerance of .015" maximum. Slop in a loose chamber.

When head clearence is set by using a long head to shoulder measurement , minimul shoulder bump, THE AREA IN FRONT OF THE BELT BECOMES UNSUPPORTED. The brass will bulge after a few firings. The round will no longer chamber. Now you need the Willis tool.

Not in my experience.

[rbuck351]

I use normal FL dies but set the sizer to stop just short of touching the shoulder and haven't had any problems with over expansion at the base on my 300 H&H. I use that method for all of my bottleneck cases.

I believe over pressure is what causes over expansion at the base. I got some well used 300 H&H brass once that had over expansion on the base but most also had loose primer pockets.

[David LaPell]

What shoulder? Lol. 300 H&H

If one would study the SAAMI chamber headspace specifications, it shows a possible tolerance of .015" maximum. Slop in a loose chamber.

When head clearence is set by using a long head to shoulder measurement , minimul shoulder bump, THE AREA IN FRONT OF THE BELT BECOMES UNSUPPORTED. The brass will bulge after a few firings. The round will no longer chamber. Now you need the Willis tool.

I tried contacting Larry Willis several times to ask a couple questions on his collet die, still waiting for a response. For now I think I will try out a couple boxes of factory ammo and go from there, keep my brass and see what happens.