The rebated rim


#1

Whilst stuck in traffic today my mind turned to cartridges. After a while, an image of a clip full of Westley-Richards 0,425" swam into my mind and it suddenly struck me that I knew nothing about the rebated rim.

Who was the first to come up with the idea? What country gets the credit and what maker produced the first rifle?What calibre was involved? Was the idea patented and if so, when?

In anticipation, Peter


#2

I know the cartridge you mean. Its an interesting question, I hope you get an answer. It certainly didn’t catch on.


#3

I disagree that the rebated rim did not “catch on”. There are certainly plenty of examples in common use. Off the top of my head, I can think of the 20x110mm Oerlikon, .284 Winchester, .41 AE, .50 Beowolf… I know of 5.56x45mm training ammunition that used a rebated rim to prevent normal, live ammunition from being used with the light-weight training bolt…

I’m sure there are many others…

AKMS


#4

Peter –

In the case of the Westley-Richards .425, I think the rebated rim was a method of using a more powerful big game catrtridge in a rifle with an action employing the standard Mauser boltface.

John E


#5

The 31 Oct 1904 DRGM (Patent) 239127 for the 11.2x60 Schüler case is the earliest reference to the ‘Rebated/Rimless’ case type that I know of. This easily predates the 1909 introduction of the 425 Westley-Richards, the earliest British case of this type.

The German patent D.R.G.M. 239127 was evidently issued for Richard Schüler in relation to the smaller rebated rim diameter of the case. The advantage was in being able to use large volume cartridges in standard systems with normal catch head. Schüler seems to have favoured the rebated rim case, as all three of their rimless cases are this type.

Other continental European use of this case type (with a significant rebate) are as follows (with ESC codes):

11.2x60 Schüler (W17)
11.2x72 Schüler (W18)
12.7x70 Schüler (W20)
8.2x52 Austrian (A30)
9.3x60 Peterlongo (A66)
10.75x63 Mauser (M57)
284/30 Fournier (FR84)
575 Miller & Greiss Magnum (W4)
9.5x66 Super Express (W78)
45 Blaser (W100)


#6

All of the adapted “big bore” AR15 calibers have rebated rims; the 499 LWR, the 50 Beowulf, the .458 SOCOM, and the 450 Bushmaster. The 284 Winchester was apparently the first U.S. rebated rim which was introduced in 1963. The .50GI, is the latest pistol caliber to have one, and the “.30 RAR” is the latest variant to have a rebated rim: http://www.ammo-one.com/30RAR.html - introduced last month.


#7

All the common Remington Ultra magnums are slightly rebeated too

425 WR actually existed with two rim diameters.The rebeated one , the most common , was to fit to standard-sized bolts

WBD ,
sorry , 575 Miller Greiss ?Did I read it right?


#8

I always liked the .425 WR. It was specifically designed to retain the bolt-face diameter and overall length of cartridges like the .30’06, so that ordinary bolt-action rifles could easily be rebarreled to take it. Given the capacity of that fat case, it could have parented a whole family of early “magnums” in various calibres, available quite cheaply. I don’t know why the H&H .375 case was successful in being so developed instead - that was basically much more expensive (Magnum Mauser action needed).

I think that all commercial rebated rim cartridges were developed for the same reason - to match the bolt face diameter of an existing gun to make conversion easy. The members of the Becker/Oerlikon family of API blowback automatics were different, however - the rim had to be small to enable the bolt to follow the cartridge into an extended chamber while the extractor was hooked around it.

I dimly recall hearing long ago of one potential disadvantage of rebated rims in hunting rifles - that there was a risk that on fast reloading, the bolt could miss the small rim and jam on the side of the case instead. Not what you want when faced by a charging beast. Perhaps that’s why the WR didn’t catch on?


#9

Pivi, re your question

The .575 Miller & Greiss case type is only known through a diagram drawn by Stephen B. Ickes (sp ??) in 1958 titled “MAGNUM MAUSER AMMO” and shown on the cover of the ICCA bulletin #347 of 1989 (see “Mauser” article).

This may only have been produced as a wildcat based on the 50 Browning MG case with a rebated rim similar to the .625 Mauser Magnum. Commercial manufacture is not known and no specimens are confirmed.

I am sure someone in this forum may well know more ??


#10

Hmmm… well, thanks for that.

Based on the recent AR-15 clones using chunky calibres and a tiny case head, the basis for the rebated rim had to be to increase muzzle energy without needing to rework the bolt face of the donor gun. I hadn’t realised that the WE .425" would fit a standard length action though.

What an inventive time it was up to the First World War! We might have perfected things since, but most of what we now have in the world of ammunition and firearms can be traced back to those years. Except for plastics and laws… and neither of those are necessarily progress.

Happy collecting, Peter


#11

So, if rebated rim is so good in allowing usage of a larger calibre barrel with an unchanged size bolt, why not to change all the guns to rebated system? Am I not catching on (to the rebated rim)?


#12

Vlad - in this case, you are “not catching on.” You’re putting the cart before the horse. The idea was to be able to use bigger diameter cartridges in very fine gun designs, perfected befrore the desire to use a bigger cartridge, without having to make huge revisions in design and tooling to accommodate them. This was especially true before CNC machinery made design changes somewhat easier to do. Lots of the original rebated rim cartridges were big game cartridges, and were not expected, and did not, sell as well as smaller cartridges for game up to the size of, say, Elk. To change the dimensions of the action of a rifle would cost more than any profit made on selling them in the bigger calibers. Of course, in many instances, they ended up changing the actions anyway, like with the Mauser short action, the normal action we know generally as the “98” with its bolt face for 8mm Mauser, and the Magnum Mauser actions.

Today, many of the rebated rim cartridges were designed so that people could convert their AR15 shooting platforms to bigger calibers.

By and large, in each case, the idea was to adapt an existing firearm to a caliber for which it was not originally designed, with an absolute minimum of effort (basically, screwing in a new barrel and perhaps some magazine box and feed guide work.

I am not a gunsmith or very technically minded (gee - that will be a surprise to the members of this Forum : ) : ) ), so this answer is probably oversimplified, but I think it is basically correct.

If you are designing a gun from scratch, then I, for one, can see no purpose at all to the rebated rim, which of itself must be carefully designed to prevent head collapse upon firing.

John Moss


#13

Vlad

What John said.

Rebated rims are an old concept but a modern one as well. They are still used by many competition shooters although the rims are not a factory product but are made for a specific cartridge/ rifle combination. The one on the right, below, is a wildcat 22 BR that was made to be fired in a rifle with a 222 bolt face. Otherwise it would have been necessary to alter the bolt, or fit a new bolt, an expensive proposition either way. Shooters will also rebate the rims on PPC cases to fit a 222 bolt face or rebate rims on BR or 308 cases to fit a PPC bolt face.

Turning down rims is another way to fit a case to a particular rifle. Turning the rim on cartridges such as the 219 Wasp to 308 dimensions was quite common when the Wasp was a popular target and varmint cartridge.

Rebated rims are very safe since the extractor groove is entirely within the solid head. You are in more danger driving on the freeways in NY or CA.

Ray


#14

Here’s a group of the 11.2 x 72 Schuler cartridges that WBD mentioned as having the rebated rim:


#15

Just for fun I wanted to see what the stress distribution in a heavy rebated case head would look like. For this purpose we have the .22 Sizzle King Warp II, a .404 Jeffery necked to .22 cal. with a .222 Rem size case head. (Probably no less practical than some actual wildcats…)

Internal dimensions are only a guess and the web may be a little thin, but that’s alright to have fun with. First we “mesh” the case (only the bottom to make it easier) to break it into tiny “elements” for analysis.

Then we set the interior pressure (including primer pocket) to 50,000 psi and restrain the case head face and rim and the case side wall for support. The results look like this…

The actual numbers may be off as I only did a quick run on this, but the stress distribution shown in color is probably valid.
What does this mean? Nothing, other than the fact that I could multi-task while watching the Yankees lose last night…

Dave


#16

Dave

Very interesting. And you have way too much free time. After those damn Yankees lose on Wed and Thur you will have a whole winter to ponder what the hell happened.

The .22 Sizzle King Warp II is probably a real cartridge. Never underestimate wildcatters. If it didn’t exist before today, it will probably exist tomorrow after certain guys on this Forum see your drawings. (Not me, but they know who they are)

I’ve shot a few rebated rim Benchrest cartridges and I know of a few really exotic others such as the short 22 BR that I showed above. I’ve never known one to fail. And Benchrest shooters are not shy when it comes to filling a case with powder. Your 50,000 psi estimate is probably off by 20%. 50,000 psi is a moderate fire-forming pressure.

Anyway, my point is that rebated rims are a perfectly safe way to expand the possibilities of a particular rifle. It’s not for the casual shooter or reloader but for an experienced guy, they are just another tool.

JMHO

Ray


#17

Ray,

As stated, just for fun and certainly not intended to challange your experienced opinion on rebated rim function and safety, etc. Rebated rims obviously work! Flaws in the analysis are inevitable for the model because of the dynamics of “event duration” (that’s a static analysis) and the fact that I have no idea how much pressure the primer pocket sees durring the very brief moment of firing. Fatigue from repeated firing is another issue entirely as well. On the other hand, it does show stress patterns in the unsupported areas of the head as well as the reduced sized column supporting the load against the bolt face. Never tried FEA on a cartridge case before and while it may be totally bogus for real world intents, the colors sure are purty…

That all being said, don’t tell anyone, but the model and analysis don’t really take that long to generate and as far as baseball, I thought '69 and '86 were better years…

Dave


#18

Hmmm. I thought 2001 was the best year of all. World Champion Arizona Diamondbacks and one of the best World Series ever!

Just wait 'til next year.

Ray


#19

It still doesn’t answer the question why have a rebated rim?. The point about allowing the designer to use a standard bolt face is valid but other than that it appears to leave the base of the cartridge unsupported and vunerable to the effects of chamber pressure. Because brass is not that strong it means more brass most be used to make the base and surely that is counterproductive? Its making the case do the job that the action should be doing. Also it means there is less rim for the extractor to get a hold of.

Would I be right in thinking is a way of making the design look more radical and not something that really has a positive place in cartridge design?

A very interesting thread though, I didn’t know there were so many rebated rims around


#20

Vince,

As it’s been said, the rebated rim is mostly for specialty applications allowing the use of a larger case diameter with a specific bolt size. Most designs are small in the difference of rim to body diameter so the case strength issues don’t really come into play on the most part. Some of the more radical designs must use very heavy case heads to avoid the concerns you mention. It should be noted that with one application the rebated rim is absolutely needed and that would be for Advanced Primer Ignition Blowback gun designs where there is no headspacing in the normal sense and the bolt diameter must be able to enter the chamber area. The round is fired “on the fly”. This is to take advantage of the bolt’s forward momentum in the chambering process as to minimize it’s mass and increase rate of fire in automatic guns.

Dave