Experimental Casull rifle cartridge with "sleeve base"?

Sorry, no photos available. so please bear with my attempt to describe these.

I visited a gentleman today who is related to Dick Casull (.454 Casull, etc fame) who showed me three rifle cartridges Dick gave him. Totally unlike anything I have ever seen.

Although the dimensions varied some, all were the same general concept, and totally unmarked. Each had a very large volume brass case, about 15-20mm across the base, and maybe 65-75mm long. They were necked down sharply to calibers roughly 6.5mm 7mm, .30 caliber with very long sharp jacketed (or maybe even solid?) bullets. However, the really odd feature was that all three had a (stainless?) steel sleeve which encased the base of the cartridge body for about 3/8" and then extended back past the rear of the base of the cartridge case about the same distance. The OD of the sleeve was the same as that of the case body, with no extractor groove or anything, so it is not a “belted” type base.

Apparently, to fire, the head of a rifle bolt would fit up inside the recess portion of the sleeve to support the base and reach the primer.

He also has a fuzzy photo of Casull with some sort of prototype semi-auto looking rifle but it was impossible to get any idea of how that might relate to these cartridges, and it may well be en entirely different project.

In conversation, it was brought out that Casull got his start working with P.O. Ackley way back, and apparently Ackley may have had contacts with Elmer Keith in the 1940s, so there are a lot of pretty smart (and opinionated!) guys who may be remotely connected.

Has anyone ever seem any cartridges like the ones described above? What was their purpose, or maybe they were just some sort of gag item made up to stump people? Wish I had photos, but not sure if I can get another invitation to see them or not.

Hi John, those prototype cartridges were developed by Richard Casull of Casull Arms Corp. back in 1996-97. The extractor groove was located inside the case head (a la Francotte-Destrée pistol cartriges) and they were made in 6.5 mm and .30 caliber. Never heard of a 7 mm but it may exist.

Fede- That’s the type!

The owner mentioned 6.5 and .30 and I was guessing maybe there might be a 7mm as there were three rounds and they looked different from each other. But, don’t go looking for one based on my casual 30 second eyeball inspection.

Any idea why this base construction was thought to have merit, either from a cartridge viewpoint or from the firearm features that would go with it?

John, there are several patents covering this design and they claim a lot of benefits, but I think that the basic idea was to make a shorter and wider cartridge case (greater powder burn area and shorter powder column) but without increasing the size and weight of the rifle. Using an internal extractor means that the outside diameter of the case could be of about the same external diameter of that of the bolt head.

That would be a cool round to have in a collection!
I bet they are rare.