Why do shot-shells [still] have rims?

[AtlSaiga 25]

Random thought.

 

I know way back in the day, all sealed cartridges had rims, I think even center-fire rounds. Than at some point (when was that btw?) they lost their rims and went with what we have today (not sure if the design has a specific name). But it seems like .22LR and shot shells kept the rims. Why? When the industry was converting over to rimless, they didn't they hop aboard. Imagine what ridiculous awesome guns we'd have nowadays if .22LR and shot shells weren't rimmed. What does this hold for the future? It seems like its too late to change now. Will shot-shells and .22 ever loose their rims?

[KennyFSU 249]

My guess is to aid in extraction.

[romad7 75]

Break action shotguns wouldnt work well otherwise.

[Mullet Man 2,114]

Break action shotguns wouldnt work well otherwise.

 

Sure they would. A different extraction claw/design is all that would be needed, atleast on self ejecting models.

 

I'm curious how you head space a plastic hull without a rim? You can't head space off the brass because of high and low bases.

[haugpatr 972]

I am going to say it would cost more to produce.

[blkgunlvr 31]

+1 for what mulletman said. Rimless cartridges headspace on the shoulder or case mouth, not very practical for a shotshell and would not allow you to use multiple shell sizes in one chamber (i.e., 2", 2-3/4" and 3" in a 3" chamber). It's been working well for a couple hundred years and there is no practical or economical advantage to changing it.

[IndyArms 10,184]

Not sure how you would LOAD the primer in a RIMFIRE ( 22 lr) if there were NO RIM... you would be back to CENTERFIRE... and that kinda defeats the whole point of RIMFIRE...

 

[tokinshitload 12]

Well, since a .22LR is a rimfire I doubt it will ever be rimless. Look into how a rimfire works. There is a company that has been working on a rimless 12g hull, but it would only work with their gun. The only benefit I see would be reducing feed problems in stacked magazines, but I think Mike found a way around that with his double stack.

xacex

[chris2000ss 2]

why re-invent the wheel. if it works dont mess with it ! sorry just my .02 cents

[patriot 7,197]

Because they ain't broke.

 

If it ain't broke, don't fix it.

[AtlSaiga 25]

In the late 19th century most if not all ammunition had rims such as this .303 British - which was centerfire.

 

 

then at some point they dropped the whole rim idea and went with what we know today, where the rim doesn't extend past the overall diameter:

 

 

why, since every other round in the world went down this road, did the .22 not follow suite way back then? I get how now its way too late to change, but that doesn't explains why it wasn't corrected.

 

The same goes for the brass base of shot shells. they COULD have chosen to design the base where the rim doesn't protrude. Why didnt they? Obviously, had they done that, the extraction methods would have been totally different over the years.

 

If shot shells and .22 didn't have protruding rims, the packaging of rounds in a magazine (box or otherwise) would be way more efficient yielding higher capacities in smaller configurations. Isn't that the Holy Grail of magazines?

 

the head spacing aspect of shot shells is a compelling one and maybe the reason why they left the rims, I guess that makes sense. But I still see no reason why .22 remained rimfire.

Edited August 4, 2012 by AtlSaiga

[ironhead7544 35]

The 22lr would need a complete redesign to function as a rimless cartridge. The bullet is a heeled type which is the same diameter as the case. The case would have to be larger in diameter to provide for headspacing. Since the firing pin crushes the case to set off the primer, designing a rimless case would be difficult. It would have to be thick enough to allow for proper extraction and soft enough for the firing pin to crush.

 

The only real advantage is that the mags could be produced easier as a rimmed case is harder to get to feed from a box type mag.

 

Concerning the shotshells, a point to headspace on is still needed. Unless you could somehow make the extractor headspace the case, this will be difficult. A magnum type belt could be used but I dont see much advantage to that.

[patriot 7,197]

Plus, the sheer number of weapons in circulation means a HUGE market for the current rimmed design, in both cases. Sales volume keeps it alive and well.

 

The 45-70 is still in production for the same reason.

 

eta: There are centerfire 22s.... 218 Bee, 222 Remington, 22 Swift, etc, ad infinitum, ad nauseum.

Edited August 4, 2012 by patriot

[csspecs 1,987]

The experimental H&K CAW had a belted case that was semi rimless. It was probably head spaced from the belt.

 

In theory one could make their own rimless shotgun shells using .50BMG cases expanded out to full case diameter.. You would of course be stuck with a single length of shell since you must head space off the front.

[romad7 75]

A 12 gauge "Auto" would be a great idea for S12s and the like. It could've done if supported by the right people, the main problem is getting guns built that would fire it. Exotic rifles rounds are possible because of the standard rim and chamber style of modern rifles, there is no 12 gauge "Auto" style shotgun (that would cycle this new round), yet but that would be pretty cool. Imagine the magazine designs that would be made possible.

 

This would be very expensive at first and very few people would shell out big bucks for it without much advantage. The 338 Lapua Mag comes to mind, this is successful because there are people willing to pay a lot of money for the added capability but a rimless shotgun isn't going to have the same advantage. Just look around here at all the effort put into firing the cheapest, crap shells, this crowd isn't going to pay a premium for this.

[G O B 3,516]

There are bazillions of 12 ga shotguns out there, and they last for years and years. The market for a rimless shotgun shell would be whatever number of new guns you could sell = a formula for economic suicide! A rimless .22 rimfire is a brainless idea the whole point of the rimfire is that it can be made CHEAPLY!

[chris2000ss 2]

rimmed shells also keep the length down .

[Freighttrain 20]

If you had a rimless 12 gauge you would have to shoot the same ammo out of the gun.If you bought a gun to shoot high brass 3" buckshot then you couldn't use cheaper 2 3/4 low brass.The rim is the only thing that head spaces the gun on a shotty.Without the rim you would have to head space off the front of the brass cup.You couldn't head space off the front of the plastic shell since it is not rigid and changes when fired.That is why we still have modern made rimmed calibers.22 in all the flavors and now the 17HMR and 17HM2.