So I am just figuring out the big problem with reloading belted magnums, in my case 300 Winchester; the rifle's headspace is gauged according to the belt, not the shoulder. However, full length sizing dies are not gauged according to the belt, but instead the shoulder. Every time we resize belted magnums in these normal dies, the shoulder is resized and set-back to spec, but because the die is set according to the shoulder, there is a slight area in the brass just above the belt that is not sized, but is instead squished back and forth, weakening the brass and setting us up for some good ol' case-head separation.

Apparently reloaders have known about this for some time, so why are major reloading manufacturers not making their belted magnum resizing dies specific to the belted magnum cases? I'm using the Lee "pace setter" dies, and I can visibly see the area above the belt that is not sized by the die, and is gradually forming a bulge just after once shot (factory 3,500 ft/lb loads, not my 4,180 ft/lb'ers). I tried only neck re-sizing with a relative's neck length dies, and after once shot with my own loads it became very difficult to chamber the next reloading of that brass, so I prefer full-length resizing. Apparently my only option is the Larry Willis die? Otherwise I'm using a wire with a bent end to painstakingly feel for excessive deformation inside the brass.

Treat magnum belted rifle brass just like non-belted brass. Size just enough that the brass will chamber with slight resistance - no more. After three or four loadings, the resistance will become great enough that a full-length sizing will be necessary. Next time sizing is required, back off the adjustment once again to preserve the useful life of the brass. When a second full-length sizing becomes necessary, that's a good time to discard the brass - you've gotten your money's worth.

I have no idea what a Larry Willis die is. May be a great and useful tool, but you might want to try partial sizing first. Good luck-

I have been shooting 7mm mag and 300 win mag in precision rifles for over 30 years. The problems you describe has always been an issue with belted magnums. I use the Innovative Technology collet bushing die (Larry Willis) to resize both of these calibers. It works great, no “belt bulge”. Make the investment, solve your issues. Good shooting.

Have the Larry Willis die also, load for the 7mm Remington Magnum in two different rifles.

loc n load gives good advice.

The Larry Willis die works on any belted case, it's a great addition

Had a gunsmith rebarrel a 270 wby for me. Match chamber , very tight.
None of my old brass would chamber. Bought the Willis die and this fixed the problem.
Also rifle dies are like rifle chambers, some tight some large. You know the problem if you chamber is min specs and your die max specs. All dies are not created equally. Try redding or Forster.

My standard RCBS 300 Win Mag dies have all the problems you say! My Bonanza (now Forster) 264 Win Mag dies have none of them!

I never noticed any problems with RCBS 375 H&H dies and have a set of Bonanza dies too. I prefer the "Collet" seating die, it helps the concentricity (bullet alignment) so much, I think everybody's competition dies use it!

I have heard about these problems for years on the Winchester and Remington belted mag cases, but both the H&H and ALL of the Weatherby Mag cases seem to be exempt! Maybe they had some control over setting the standards for their rounds! And Remington & Winchester were more interested in mass production than "Proper Precision"!

Ivan

Chamber & reamer specs have always been all over the board on belted cases. The belt was useful for the first belted cases; 300 & 375 h&h, the 458wm.
If you want best results, always headspace off the shoulder. Even if you have a rimmed case with shoulder, headspace off the shoulder. You dont need special dies either. Partial FL dies adjusted for correct headspace easily double brass life.

__________________
NRA Cert. Inst. IDPA CSO

Not to be contrary but, My school of thought is, If I make reloaded ammo, I want it to be the best possible for my gun, BUT, I want it to also fit in any gun chambered for that round. One of my B-I-L's also hunts with 300 Win Mag, as does his brother. I want to be able to exchange ammo, if the need arises.

The exception to that rule are some over pressure rounds! I have one 223 that is loaded way hot for 1000 yard shooting. I don't want those to fit in someone's AR (especially my AR) !!!

I guess I grew up in the "Age of Plenty", if I only get 5 reloading's instead of more, that is the cost of shooting. One the other hand I just retired 250 Hornady Match 308 brass, that isn't worn out at 17 firings! I'm just switching to Lapua Match brass and I'm doing the same with my 338 LM too. The retired 308's become AR food, the 338's go on the shelf.

Ivan

Sure, if you are loading for more than one rifle then giving up headspace & brass life is fine for reliability. Just pointing out the belt on many of the magnums is pointless. It was put on cases to start with that had a long sloping shoulder or no shoulder. The ammo companies picked it up for the ability to share cases with diff calibers. Its really a pointless item on a modern shouldered case.
I have a Ruger #1S in 7remmag that i had Dakota convert to 7mm Dakota. Very nice round, no stupid belt. The 404jeffery had a sim long sloping shoulder as the h&h magnums but doesn't ha pve a belt & works fine without one.

__________________
NRA Cert. Inst. IDPA CSO

I’ve been reloading belted cartridges for a few years....28 years. As mentioned, you run it in a full length sizing die....just far enough to “kiss” the shoulder. A gentle “kiss”. I get about 10 firings on my .375 AI , pushed hard, before discarding the brass. Using this method, I get slight resistance to bolt closure...they don’t fit “sloppy” like a factory round would! memtb

Most people that bought "Belted Case" rifles did not worry about reloading their ammo back in the day.

Sort of like people that bought Weatherby rifles..............

The cost of buying ammo was the least of their problems.

I also use the IT die to size my brass to the belt. I bought it quite a while ago to size brass to fit my rifle.. Yeah you can do it with neck sizing. etc etc...I want that round to fit the rifle not be tight loose or anything else. I got much brass given to me and I needed it to work right. The only belted rounds I have left these days that I shoot is a 300 Win mag in a pretty Kimber...a 300 H&H in a Remington 721 and a Win M-70 338 Win Mag(1st year gun in the caliber). To be honest the old Remington is the one I will keep as it shoots fine. The other pretty guns are just that..pretty. That IT die keeps the 300 H&H brass going for up to 20 reloads as long as I don't push 'em too much and expand the primer pockets

I haven't had issues with brass only fired in a given belted magnum using the Lee dies. I however had the chambering issue as a result of a bulge on some once fired brass I bought for a Howa 300WM. Found a Lee 7mm STW set of dies in clearance at BPS for $9. Took the sizing die, chopped the top off and shaved a little off the bottom so it would go all the way to the belt. Used it to knock the bulge off the brass and all has been well since.

I had looked at that Larry Willis die, but that was just too much for me to stomach to salvage a handful of brass. I suppose if I was having the issue on a regular basis or loaded a ton of belted mag brass with the issue, it might be worth the investment.

Rosewood

I just neck size my 375H&H.
When it time to squash the case shoulder back I use an RSBS precision mic tool to help setup how much full length sizing is required.

It not just belted magnums that can experience case head separation.
Fl sizing grows the cases the brass flows from the web.
My reloading manuals say after 5 case trimmings you should be probing for the thinning ring around the web.
I never had much luck determining the depth of the thinning ring by probing so after 5 trimmings I cut a case in half lengthwise and look how bad the ring is in my batch of cases.