Rimless straight wall cartridge?

Cleftwynd

Cleftwynd

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Belted cases headspace on the belt, rimless and rebated cases headspace on the shoulder, rimmed cases headspace on the rim. I know all this stuff but am staring at a rimless straight wall casing and it started me thinking....

First to explain, while adding a small mod to the chargemaster, I cut off the neck and shoulder of a 7mm08, since it was a nickle casing and was pretty shiny (I kind of like shiny things), I decided to trim and deburr the remainder. I have had it sitting on the bench for a while and it keeps catching my attention. It looks a lot like a fairly large straight wall pistol cartridge, but rimless and close to a 45 cal in diameter.

How would you headspace a rimless straight wall rifle cartridge, or is it even possible? The benefits of a rimless in magazines is quite obvious, and this stupid piece of nickle plated brass just won't leave me alone! It just cries out to be loaded for a beautiful blued steel and well figured walnut rifle os some sort. Being rimless would have its benefits, but can it be done with a larger casing closer to rifle than pistol? I know there are a few rimless, straight wall pistol cartridges, but something closer to say 45-55 rimless would be neat!


Forgive me if this has been done, but I haven't found anything in the short time I searched.
 
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I knew those used the case mouth, but they are rather small compared to a rifle sized casing. I guess it should work then! Something like a 308 necked up to a straight wall.
 
I thought the belt was only used to headspace cartridges that don't have a shoulder?

I don't remember where I read it but I can remember reading that the belt was included on older magnum cartridges because it was expected on all "magnum" cartridges whether it was required or not. Most modern (post 1950) belted cartridges with belts only include it as it was part of the parent cartridge (often the .375 H&H) but isn't really required as it can headspace off of the shoulder.
 
As far as I knew belted headspace off the belt, but CAN headspace off the shoulder, I could be wrong though, it happens from time to time.

Maybe someone more knowledgable will step in.
 
LUTNIT said:
I thought the belt was only used to headspace cartridges that don't have a shoulder?

I don't remember where I read it but I can remember reading that the belt was included on older magnum cartridges because it was expected on all "magnum" cartridges whether it was required or not. Most modern (post 1950) belted cartridges with belts only include it as it was part of the parent cartridge (often the .375 H&H) but isn't really required as it can headspace off of the shoulder.
Click to expand...

I have a magazine called Shooting Times, December-January issue and it says something similar.

"I only own one belted magnum rifle, and it's a 375 H&H. Why? It actually need's the belt. The narrow shoulder could not provide positive headspace support when the firing pin did it's best to drive the case deeper into the chamber. The belt and it's corresponding step in the chamber provided the case a positive stop to resist the firing pin blow."
 
straight wall pistol cases are meant to headspace on the mouth,but they can actually headspace on the extractor/rim if they are a bit short.
 
Headspacing off the case mouth does not work well with fullbore rifle cartridges. Some (but not the original) versions of the .400 Whelen do not have a large enough shoulder to reliably hold the case against the blow of the firing pin, for example.
 
Look at the 50 cal beowulf. It headspaces off the mouth of the case. Neat lil round and in aa rifle hits like a sledge hammer at fairly close range. Its designed for the ar platform but would make a nice plinker in a bolt gun
 
In order to headspace on the case mouth the firing pin blow must be relatively soft as in a pistol. Most rifle pins exceed the thrust threshold for case mouth headspacing. This is because the rifle primer cups are much thicker and harder to contain the 60,000 + psi developed by modern centerfire rifles.

The cut off case you keep looking at is an extra long 44 Automag from the 70's which died in relative infancy. This was a selfloading pistol of unique design specific to this cartridge which was nothing more than a cut off 308 case using a .429 240gn bullet shoved in it. It was a very high intensity cartridge and the guns shot loose very quick and misfires were common. Headspace was unreliable and it was plagued with problems. Serious collector value now.
 
You would end up with a 1.9" 45ACP. The 45 win magnum semi auto is heading in the same direction.

rimless 45-70

has it been done, don't recall much info but I am sure someone has thought about it too.

Watch that trim length so that you can good fit AFTER the taper crimp

moderate pressures and have at it.

You might even be able to just run a 45ACP reamer in deep. use a 452 bore so you will not get case bulge. 458 bullets is likely too big to fit in a 473" diameter case.

A very interesting brush buster.

Jerry
 
Also the .50 Razorback, which is based from the .300 RUM blown out to take a .510 diameter boolit and trimmed to 2.375".

images



http://castboolits.gunloads.com/showthread.php?115952-50-RazorBack-done
 
Some absolutely great info here! Thanks fellas!

It sounds doable, but trim length, brass thickness, primer strength, etc...all would become critical. Probably too much headache to be viable, however it still interests me.

It sounds like chamber tolerances would have to be held very tight as well for the reasons both Douglass and Jerry stated. A rimmed casing makes a lot more sense, I just never cared for rimmed cartridges in magazines, excluding tubular of course. In fact that is the only thing I never liked about my 303.

Maybe one day I will set back and ream out a barrel and try this, I think a 18-20" barrelled bolt action, DBM open sighted rifle with a cartridge like this could be a nice short range deer/bear gun. Or an older auto with those dimensions. Case feeding and extraction should be very smooth, especially with the rounds capable of stacking so evenly in a magazine and no rim to catch on anything. All that with a heavy slug at half decent velocity!!
 
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