Numbered Gibbs cartridges question

I’ve just lately grown curious about the Gibbs numbered cartridges. The .360 No. 3 is pretty well established by specimens. Has the .360 No. 4 been confirmed by specimen(s)? Is there a Gibbs No. 5? &c., &c. Anyone help cure my ignorance here?

These are the Gibbs numbered cartridges of which I have information:

.461 No. 1
.461 No. 2
.360 No. 3
.360 No. 4
.360 No. 41/2

As far as I know, specimens of No. 4 and 41/2 are not reported to exist.

Thanks, Fede. Can you describe the form of the No. 4 1/2 case (straight, necked, length, &c.)?

Chamber dimensions indicates a slightly necked case with these measurements: lenght 1.53" (38.86 mm), rim diameter .440" (11.17 mm), head diameter .380" (9.65 mm) and rim thickness .080 (2.03 mm).

Thanks again. Were these dimensions taken from a chamber cast? With the action open or closed?

Sorry, I don’t know. I took this information from “British Single Shot Rifles, Volume 2, George Gibbs” by Wal Winfer but didn’t noted if it was from a chamber cast or any other details. As I don’t have a copy with me right now you may have to wait until next week to know this, as long as it is mentioned in the book. Maybe another member of this forum have a copy at hand.

I have the book. Thanks for giving me the reference. Should have thought of it myself!

The Gibbs “.360 No. 4 1/2” is just a name made up by Wal Winfer for a chamber cast, which he misunderstood, from a .360 No. 5 rifle. There is no “unknown” or “experimental” Gibbs cartridge involved – the “No. 4 1/2” does not exist. The chamber dimensions are clearly for the .360 No. 5 cartridge. And the .360 No. 5 was definitely designed as a rifle cartridge, but evidently not by Gibbs

Sorry, but I thought you should know.

Very interesting, is this mentioned in the book and I missed it or did you reach this conlusion by comparing both chamber casts taken from Gibbs rifles?

Of course it is not in the book. Winfer could not compare chamber casts from two Gibbs rifles, so I certainly could not. I came to my conclusion by comparing the measurements given in the book with cartridge measurements from Fleming, given allowance for the difference between chambers and cartridges intended for them. I am still trying to get cartridge measurements for Eley .360 shotshells to see if the chamber will accept both .360 No. 5 and .360 shotshells.

In any event, the “neck” diameter of the “chamber” is too small to accept the neck of any .360 rifle cartridge. It is of bullet diameter and is merely a long throat, added to improve accuracy by allowing the bullet to be chambered without damage from the end of the rifling.

I have received measurements from several different .360 shotshells. They are all too large in diameter to fit the chamber in question.