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Belted Magnum Cartridges

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Old 11-07-2006, 06:41 AM
Silver Member
Join Date: Nov 2005
Location: Texas
Posts: 226
Re: Belted Magnum Cartridges

Has anybody ever used the innovative technologies belted magnum sizing die? www.larrywillis.com
he claims this is the answer to the swelling in the case just above the belt. I have little experiance with belted cases and I'm wanting to build a 300weatherby. I figured I could control the chamber dementions right there? Any more suggestion for me and slopeshunter.

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Old 11-07-2006, 05:46 PM
Silver Member
Join Date: Sep 2001
Location: medford wi usa
Posts: 273
Re: Belted Magnum Cartridges

I have the die. It is only needed when you have a sloppy chamber. My friend has a couple of custom weatherby's that do shoot great but for some reason the chamber must be "generous" right there. After resizing it leaves an ever so slight bulge above the belt. No sizing die I know of goes all the way to the belt for sizing....that all stop just short and that's where you can have a problem. I've only needed to use that die on his rifles ......I myself own 7 belted mag cartridge guns and haven't needed the die on my guns. BUT, the die is high quality....works as well as advertised....and helped us reclaim a couple hundred once once fired weatherby cases which quickly paid for the die.
If you have the problem this will cure it. Kind of like pennecilin.....if you aren't sick you don't need it....if you are it works!@!
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Old 11-07-2006, 07:15 PM
Platinum Member
Join Date: Dec 2005
Posts: 2,114
Re: Belted Magnum Cartridges

Has anybody ever used the innovative technologies belted magnum sizing die? www.larrywillis.com
he claims this is the answer to the swelling in the case just above the belt.

[/ QUOTE ]Most of the folks who years ago shot 28 and 30 caliber magnums in 1000-yard matches winning most of them and setting records along the way did just that. And their chambers were normal SAAMI minimum sizes. But they used a regular full-length sizing die cut off just above the belt clearance recess as well as a bit below the die's shoulder then truing and cleaning up the edges so they're not sharp. This "body sizing" die needs to be set in the press such that the bottom of it touches the belt when the ram's at the top of its stroke. Doing this reduced fired belted case body diameters all the way to the belt whereas regular full-length sizing dies stopped short. By making the fired belted cases size back to almost new case dimensions, accuracy was excellent and surpassed any type of neck or partial neck sizing. Nothing's changed since then.

Some top long range shooters asked top die makers to make a body sizing die to use after sizing fired belted cases first with a conventional die. But they didn't think enough would be sold to make it worthwhile.

I've always got best accuracy with .30-.338 Win. Mag., .30-.338 Keele Mag. (same body size as standard .30-.338 but uses .300 Win. Mag. cases to have a much longer neck) and the .300 Win. Mag. using new cases or fired ones full-length sized with a conventional die, then using the body die to size the body all the way to the belt back to almost new case dimensions. Setting the shoulder back about .005-inch from its fired position and letting the sized cases headspace on the belt like they're supposed to allows cases to be fired and resized at least 15 times. Some folks report over 20 reloads per case using a regular full-length followed by the body sizing die. And 1/2 to 2/3 MOA accuracy at 1000 yards is about normal with good barrels and match bullets. One can expect sub MOA accuracy through 200 and maybe 300 yards with hunting bullets using this method. I'm talking about accuracy being determined by shooting at least 15 shots per test group.

Neck sizing fired belted cases lets the shoulder be far enough away from the head that when chambered, the swelled section directly in front of the belt is held clear of the belt headspacing shoulder at the back of the barrel's chamber. If this swelled section isn't reduced back to about new case dimensions and normal full-length sizing dies are used, that swelled section, or step, will interfere with the headspacing belt in the chamber and hurt accuracy. All this is why most folks get better accuracy with neck sized belted cases. Size that step back down and great things will happen.
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Old 11-08-2006, 06:08 AM
Platinum Member
Join Date: Dec 2005
Posts: 2,114
Re: Belted Magnum Cartridges

Has anybody ever used the innovative technologies belted magnum sizing die? www.larrywillis.com he claims this is the answer to the swelling in the case just above the belt.

[/ QUOTE ]Larry Willis states in his web site about full-length belted cases:

"The belt on a belted magnum case prevents any conventional resizing die from traveling far enough down the case. Then as the case is withdrawn, the brass also 'springs back' slightly."

I disagree with that. As the belt doesn't touch any part of a traditional belted case full-length sizing die, it's not the belt's fault. The die's got a relief area cut out of its base so the belt won't be touched. And part of that relief cut extends several thousandths of an inch in front of where the case belt is when the bottom of the die contacts the shell holder.

Here's what Fred Huntington (RCBS founder/owner) told me back in the early 1970's. Die makers don't dare make a belted case full-length sizing die that would size completely to the belt. As belted cases have the tightest headspace tolerances for both new cases and headspace gages, most folks wouldn't take the time to pay attention to the details of precice die position in the press. Too many people would set the die too far down and end up crushing the front edge of the belt causing headspace problems.

So it's not the belt on the case causing the problem. It's the way dies are made because most folks won't correctly set up a die that sizes a fired belted case all the way to the belt without damaging the belt and causing headspace problems. However, one can learn to set one of these collet type body dies correctly. It may take some time and careful inspecting along with some trial and error routines, but it can be done.

One of the greatest myths about belted cases is they were made that way to increase their strength at that point. Nothing could be further from the truth. Holland & Holland put that belt on some of their flanged (British term for rimmed) cases used only in double rifles so the same cartridge could also be used in a staggered box magazine bolt action rifle. Huge, rimmed cases don't feed reliably from such magazines. And the long, tapered shoulder on cases they used needed something at their back end to headspace on else the case would be driven too far forward in the chamber causing all sorts of extraction and head separation problems. That belt prevents the cartridge from catching the back end of one below it in the magazine and not letting the bolt push it forward into the chamber which happens with rimmed cases in staggered box magazines.
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