Sizing Belted Magnums or (How I stopped worrying and embraced the false shoulder)

[Chuck R.]

As per this thread:

Belted Magnum Brass Prep: False Shoulder?

Working with my newly re-barreled 300WM and I'm getting 0.020" average headspace expansion on new FED brass using a Hornady comparator and taking 10rd samples. New brass just had the necks sized, no shoulder bump. AVG Measurement for new brass was 4.264" AVG measurement for once fired is...

www.thehighroad.org

I've been playing with creating a false shoulder when 1st time sizing belted magnum brass IOT minimize case stretching from the web area. This started with a new Bartlein barrel on my 700 and some seriously undersized new FC brass (made to headspace on the belt VS shoulder as per normal specs).

The intent was to use the false shoulder to keep the case head against the bolt (same effect as jamming a bullet) and get the brass to form without the normal stretching at the web. Extra time involved is about 10 minutes per 50 rds. Idea came from here:

https://www.handloadermagazine.com/7mm-remington-magnum

Another issue was even with the 1st firing, the brass hadn't expanded enough to have any resistance when closing a stripped bolt. So IF a did the standard; measure, subtract .002-3" to set up my sizing die, I'm still "short" and headspacing on the belt .

The steps I used:

1. Run the .32 neck expander into brass
2. Run a .338 neck expander into brass (.32 wasn't enough of a false neck and I lost 2 pieces of brass going right to .33)
3. Neck size to achieve a "crush fit" on the false shoulder created in step 2. I used my die set up for FL sizing and backed it off using a 0.0245" die shim.
4. Load. I used a bunch of Midway 168 OTM "2nds" that I bought for practice.

I've been shooting this as practice loads while fire-forming, it's a full power load; 168 grn at 3179FPS, accuracy has been running just under MOA consistently, easily stays on my swinger at 547 yds. The load mimics my Nosler ABLR 168 grn load.

Some measurements (20 cases each method, Hornady comparator, caliper NOT set to "0"):

AVG Measurement for new brass was 4.264"
AVG measurement for once fired brass (without false shoulder) is 4.284", SD was 0.009 (.020" expansion!!)
AVG measurement for once fired brass (with false shoulder) is 4.286", SD was 0.008 Gained .002"

The good news is, with the false shouldered brass out of 50 rds I had 5 that formed enough to offer resistance while chambering. The non-false shouldered brass chambered with zero resistance for all 50rds, bolt just dropped.

So for this next loading at least I've set my "bump" to 4.286" and will track through the next loading.

So, does it work?

I dunno.. yet.

Using my RCBS "pick" I'm not feeling much of a difference in the web area. Teslong Bore scope showed the same. I am happy about the extra .002" in case expansion on the initial firing. I now have 50rds of normal sized and 100rds of the initial fire forming using the false shoulder. I'll continue to track firings, and expansion for both lots and see what happens after multiple firings.

 

[jmorris]

Depending on the load, sometimes brass needs to be fired a number of times to fully form to the chamber.

Custom die makers often want 3 or more firings from a given chamber.

 

[Slamfire]

I really hate the belted magnum. For decades I read in print articles praising belted magnum cases, and now that I can stand on my own, I realize just how little those writers knew about good case design. Belted magnums were a solution for double barrel rifles loaded from the breech. Belted magnums are terrible cartridges in magazine guns, for one, rim lock with a belted magnum is real. I have experienced it in my 375 H&H. The bottom rounds slide enough, so the belt on the top round, was behind the rim on the cartridge below. That caused rim lock, and it took pulling the bolt back, pushing on the stack with my thumb, to reorient the cartridges in the magazine. In an emergency situation, having to figure out why your rifle is jammed, will get you killed before you come up with a solution.

And then, the base to shoulder distance is not controlled on belted magnums. The cartridge headspaces on the belt. The end result, the cartridge can be really stretched on first firing. And then if the shoulder is bumped back too much on reloading, the second firing will also stretch the sidewalls. Do this a couple more cycles and case head separations will occur. I had to buy special Wilson cartridge case headspace gauges, which allowed me to find the position of the shoulder, so on resizing I would not bump the shoulder back more than 0.003".

However, there is a total solution to this. Lubricate your cases. If you leave sizing lube, or manually grease up your belted magnum cases, the front of the case won't stick to the chamber as the pressures rise. Instead, the case will slide to the bolt face, the shoulder will fold out to fill the chamber, and you will end up with a perfectly fireformed, and stress free cartridge.

This is what I did on my expensive, new 300 H&H cartridges.

A dip and a twist in hair gel. Hair gel is vasoline with perfume. It is non toxic so sucking my fingers at the range will not turn me into a dead bug. Any grease will work, but I have decided I am safer with human compatible greases instead of industrial greases. Case lube would work just fine, but I wash my cases after sizing. I don't have to, but I do.

fired case below greased case

When I get back, I use that special Wilson gauge to determine how far forward the shoulder moved, and I bump the shoulder back, in the sizing die, about 0.003" Unfortunately, that base to shoulder distance is unique to each and every belted magnum of the same caliber, as base to shoulder distance is not controlled in belted magnums.


Greased rounds shoot well.

by the way, it is obvious that the H&H company loaded their 300 H&H Magnum cartridges to lower pressures than SAAMI standards. The H&H cartridge is pushing a 150 grain bullet at 3000 fps. That is a bit faster than a 30-06. Gunwriters have claimed the British loaded their rounds light because of African heat. I see nothing to support that, other than Africa does have hot weather. I am going to claim, H&H was loading the 300 H&H light, because they were using commercial Mauser actions, made of plain carbon steels, designed for 43,300 psia 8mm Mauser cartridges, and those actions would not hold up to 65,000 psia American loads.

 

[Chuck R.]

Depending on the load, sometimes brass needs to be fired a number of times to fully form to the chamber.

Custom die makers often want 3 or more firings from a given chamber.

Yup, realize that.

Just trying to minimize how much of the brass comes from the web while it's expanding.

Rather than "hair jell" or another lube, I've left the resizing lube on, with similar results.

 

[jmorris]

And then, the base to shoulder distance is not controlled on belted magnums. The cartridge headspaces on the belt. The end result, the cartridge can be really stretched on first firing. And then if the shoulder is bumped back too much on reloading, the second firing will also stretch the sidewalls. Do this a couple more cycles and case head separations will occur. I had to buy special Wilson cartridge case headspace gauges, which allowed me to find the position of the shoulder, so on resizing I would not bump the shoulder back more than 0.003".

I find this method to work just as well on belted rounds as regular ones.

Setting size die for bolt action rifle.

www.youtube.com

Of course they have to be "blown out" enough that the bolt doesn't free fall with a fired and unsized case.

 

[Jim Watson]

Belted magnums were a solution for double barrel rifles loaded from the breech.

Strange, I always thought the belted case was to get solid head spacing of very tapered cases in bolt actions.
If you wanted a double, you should get the superior "flanged" version.

I don't know who developed the trick extractor for belted and rimless cartridges in break actions, but Westley Richards was an early user and promoted it heavily. They also said their single trigger was sturdy enough for a dangerous game rifle. But they were a Birmingham brand.

The only olde English user of the belted case in CotW besides Holland's was BSA who used it for a couple of bolt action rounds that did not catch on.

rim lock with a belted magnum is real. I have experienced it in my 375 H&H.

How dreadful, since box magazines were what I thought to be the whole basis for the belted cartridge.

 

[Chuck R.]

I find this method to work just as well on belted rounds as regular ones.

Setting size die for bolt action rifle.

www.youtube.com

Of course they have to be "blown out" enough that the bolt doesn't free fall with a fired and unsized case.

and this is the crux of the issue right now..

 

[jmorris]

Just keep your die high enough to not shove the shoulder back but low enough the neck is sized well enough to hold a bullet.

At some point it will quit fitting and you can set your die.

 

[Chuck R.]

Just keep your die high enough to not shove the shoulder back but low enough the neck is sized well enough to hold a bullet.

At some point it will quit fitting and you can set your die.

That's exactly what I'm doing.. and becoming a freaking expert at Rem 700 "rapid bolt stripping and reassembly" while I'm at it.

 

[lightman]

I set my dies up the same way with belted magnum cases as I do with any other bottle neck case. You can't do much about case stretch on the first firing if the shoulder is pushed back more than you like. But after the first firing I size them to fit the chamber. One of the older gun writers once said to treat the belt like the useless appendage that it is! And I took it to heart!
A long time before there were so many measuring devices on the market I would start sizing with the die a little above the shell holder, maybe 1/16th inch or so, and begin watching the case neck as I adjusted the die down until the sizing mark met the shoulder. About the same way that you use a measuring tool except by eyeball.

 

[Varminterror]

even with the 1st firing, the brass hadn't expanded enough to have any resistance when closing a stripped bolt. So IF a did the standard; measure, subtract .002-3" to set up my sizing die, I'm still "short" and headspacing on the belt .

I wish folks would stop telling new reloaders to measure fired brass to set their sizing dies. So much headache would be averted.

Your instance here, the fired cases were still short. In other instances - like the one I helped another loader with YESTERDAY - the loader will find out their fired brass was actually oversized and bumping back 2 thou still didn’t actually fit into the rifle.

So that really is the game. Even with virgin brass, I set my sizing die with my chamber: if I need to push back, I will, but typically it ends up under length, so I use shim tape to discover by how much, and if it’s more than 4-5 thou under, I pull up a false shoulder. Not just belted mags, all cartridges. Pull up the false shoulder, neck down, anneal, size again the the desired bump and expand, load. An LCT makes quick work of it.

 

[Varminterror]

You can't do much about case stretch on the first firing if the shoulder is pushed back more than you like.

The point of this thread is that you CAN prevent case stretch on the first firing, by pulling up a false shoulder. That’s literally the proposed premise of the thread…

 

[Chuck R.]

I wish folks would stop telling new reloaders to measure fired brass to set their sizing dies. So much headache would be averted.

Your instance here, the fired cases were still short. In other instances - like the one I helped another loader with YESTERDAY - the loader will find out their fired brass was actually oversized and bumping back 2 thou still didn’t actually fit into the rifle.

So that really is the game. Even with virgin brass, I set my sizing die with my chamber: if I need to push back, I will, but typically it ends up under length, so I use shim tape to discover by how much, and if it’s more than 4-5 thou under, I pull up a false shoulder. Not just belted mags, all cartridges. Pull up the false shoulder, neck down, anneal, size again the the desired bump and expand, load. An LCT makes quick work of it.

Now that is a neat trick!

I've been annealing 1st, why do you anneal after creating the false shoulder and sizing??

LCT??

 

[Jim Watson]

Slamfire just butters them.

 

[Varminterror]

Now that is a neat trick!

I've been annealing 1st, why do you anneal after creating the false shoulder and sizing??

LCT??

In general, virgin brass is annealed before it leaves factory. So I pull up the diameter, then push back down part of the neck, which means I work hardened the hell out of that brass - so I anneal it after forming the false shoulder, size again, which does nearly nothing but is a good confirmation step, then neck expand, and I’m ready to load.

LCT = Lee Classic Turret. Have multiple expander dies in a row if needed, plus then the sizing die, and then coming back after annealing, I hit it with the sizer and a proper sized neck expander. Trim, DB & C, prime, charge, load, bang.

 

[Slamfire]

Strange, I always thought the belted case was to get solid head spacing of very tapered cases in bolt actions.
If you wanted a double, you should get the superior "flanged" version. [/quote}

You are right, I was wrong. Looked at my H&H Catalogs, the earliest is to the 1930's, only rimmed cartridges are being used in H&H double rifles, and only H&H belted cartridges are being used in the bolt guns. Searching the history of belted Magnums

400/375 BELTED NITRO EXPRESS (H&H)

early "rims", "ledges" are there to fix the cartridge in the chamber. Does not mean the earliest are being used for bolt guns, and since I cannot find the 1905 H&H patent, I don't know what functionality H&H is claiming. In so far as the belt, I agree with this author that the belt was not needed:

"Belted" cartridges [Archive] - The Firing Line Forums

[Archive] "Belted" cartridges The Art of the Rifle: General

thefiringline.com

The first use of a belt on a commercial cartridge appears to have been on the .400/.375 Nitro Express, introduced by Holland & Holland in 1905.

The round has a very small shoulder, so it was probably felt that it was needed for adequate headspacing -- it well may have been -- but I find it to be kind of questionable given the low pressures developed by most of the British cartridges of this time, which used cordite as the propellant.

Another reason I question the necessity of a belt on such a cartridge is seen in two other cartridges from the same time frame, the .404 Jeffrey, from around 1910, and the .425 Wesley Richards, circa 1909. Both had shallow, sloping necks that were in many ways very similar to that on the .400/.375, and not nearly as pronounced as the neck on the .375. And another H&H cartridge from the same time frame, the .275 Magnum, has a very pronounced shoulder, one that is more than adequate to serve as a headspacing point.

As far as other manufacturers in Britain that used belted cartridges in their designs? As far as I can tell, only BSA attempted to make a run at the design with their .26 and .33 Nitro Express rounds, neither of which ever made much of a splash in the cartridge world.

In fact, the necks on the .375 and the .416 Rigby appear to be very similar, yet the .416 has no belt, and from all accounts never even came close to needing one. Given that it's still loaded, and used, today for dangerous game, one would think that were any headspacing problems to be expected they would have shown up by now.

I'm firmly of the opinion, and it bears out in my experience, that the belt is, for the handloader, a much greater pain in the ass than benefit.

Another point to look at is Germany, which was as important and vibrant in the world of cartridge development as Britain. Some German designs also show longish, sloping necks, or rather small necks in proportion to the size of the cartridge (9x71 Peterlongo, 9x56 Mannlicher-Schoenauer), yet the only German-developed belted cartridge was the 7x73 Vom Hofe.

Well, I will caveat that somewhat -- the Germans did use a number of belted cartridges in military applications, mainly for Mauser aircraft machine guns and machine cannons. In such a situation as a high rate of fire gun, I can see the belt being a much better way of headspacing for surety of operation as opposed to a pronounced rim.

How dreadful, since box magazines were what I thought to be the whole basis for the belted cartridge.

Oh yes, how awful. Reality bites. How can anyone expect cartridge designs with external ridges, rims, etc, not to ever jam? It is obvious in hindsight. Even more obvious when it happens.

 

[jmorris]

I wish folks would stop telling new reloaders to measure fired brass to set their sizing dies. So much headache would be averted.

A lot of the problem is people who just introduced themselves to measuring instruments as well as reloading, just compounded the learning curve problem.

I can see the argument for both sides but when it works better, KISS is the way I go. Save the other stuff for problem solving.

 

[Slamfire]

I wish folks would stop telling new reloaders to measure fired brass to set their sizing dies. So much headache would be averted.

Your instance here, the fired cases were still short. In other instances - like the one I helped another loader with YESTERDAY - the loader will find out their fired brass was actually oversized and bumping back 2 thou still didn’t actually fit into the rifle.

I am confused about this statement. Not the part about measuring fired brass, but the part, as if I understand it correctly, that fired cases come out shorter than the chamber. That will only happen if the internal case pressures are not enough to stretch the case sidewalls, and that does happen, given high case to chamber friction, and low internal pressures. It is my recollection that Professor Boatwright calculated that 27,000 psia was the pressure needed to stretch 243 Win brass sidewalls. Given enough case to chamber friction to fix the case in the chamber, it is possible to duplicate PO Ackley's famous trick of firing a 30-30 Ackley case in a lever action, said action having the locking lugs removed, and not have the bolt blow out. (PO Ackley did not measure case pressures for this experiment)

By the way, ole PO never duplicated that experiment with a 30-06 Ackley Improved. The 30-06AI runs close to proof pressure, and cutting the lugs off the bolt, firing a 30-06AI would have resulted in a lugless bolt making it into low earth orbit. No 30-06 case is strong enough to hold 70K psia pressures without support. PO Ackley was creating psuedo science experiments to sell his snake oil case designs.

 

[MEHavey]

I could see a foreshortened case happening on firing IF . . .
- The case/chamber was slick/lubed to where it didn't lock itself at front
- The load was insufficient to blow the shoulder fully forward, but rather only expand the body
(a delicate dance to be sure)

But then I would merely size enough to determine where the 'squeezed' case grew back in length to contact the chamber shoulder on closing again....
And call that dimension "baseline" headspace.
...and adjust from there.