I found the following in the December 1964 edition of the MLAGBs 'Black Powder' magazine.
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"Terry's cartridge was made of nitrated brown paper, secured behind the powder. At this end is glued a tallow saturated wad, designed to remove fouling and also create a gas check - for the explosion takes place from the centre, not at the end, of the cartridge; the percussion nipple is therefore situated  mid-way along the chamber. The nipple itself tapers from a wide mouth to normal size. "By being so formed," wrote Terry, "a greater explosion power is obtained to burst the carridge and ignite the charge."

After firing, the wad remains in the barrel, ready to be forced forwards by the next cartridge. A bullet of the same design and weight as for the .577 Enfield was used, .54" nominal.
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I also have an unsigned manuscript from the MLAGB  archives ""Small Arms of the British Service, 1866" which says under the heading "Terry's Breech-Loading Carbine."
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Ammnition, special. Pritchett bullet, weight 530 grs; diameter .568; length .953in; charge of powder 2 drms.
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There's conflicting information on the bullet diameter but I hope this helps.

David

Yes, I have a Facebook page.

David

There appears to be both a slot in the bolt and the 'reciever body'. Do the two marry up when the action is closed? No sure why though?

David