Phil

Was that 56 grains of Cordite? If so, that's unusual - most 450/400 x 3 inch Nitro rifles are regulated for 55 grains?

Certainly so with Jeffery's rifles, and he was the originator of the round. It was originally called .400S Jeffery.In terms of exterior ballistics, there is no difference when compared with the longer case - Jeffery's main concern was to develop a cartridge that couldn't be chambered in a gun with 31/4 inch chambers built for Black Powder - in this case the strategum was the thicker rim and the shoulder being set further forward - the thicker rim having the benefit of being stronger.

The photos of "your" A. Hollis have a Jeffery "look" about it; almost certainly made by the same manufacturer that Jeffery, Wilkes, and many others used. As observed in other posts, this was H. Leonard & Co who vey rarely signed his own guns.

As has also been observed in other posts, A. Hollis ought not be confused with I. Hollis who made some pretty ordinary shotguns. But I (Isaac) had his moments too, and one should always remember that you should never, metaphorically speaking, "judge a book by it's cover" when it comes to English guns.