Hello Gents.......
Thankyou for the warm welcome, I have watched these forums for quite some time and finally decided to join.
Have enjoyed BPE, Nitro Express, and "Bore size" rifle shooting for years. Developed the "British Rifle" bug when I was based at RAF Bentwaters, UK back in the old days.

The .500 3" Ingram is 8lbs 13oz with 28" barrels, BP proof marks ".577ex" indicate that it was done after the introduction of the updated proof standards of 1887. There are no Ingram records extant to narrow down the date any better.
Rifle shoots very nicely with 59.5grains of H4198 and a 440 grain paper patch cast from 1:30 tin/lead

My newly acquired .577 3" Grant was made in 1873, Jones under lever, with keyed forend retention. 26" Damascus barrels, weighs 8lbs 14oz, and I'm told it likely was regulated for an early .577 3" 160-480 load.
Not shot it for groups yet, too cold here to spend a lot of time at a bench, but it works great with 160 grains of Swiss 1 1/2 F and a 500grain paper patch of same 1:30 tin/lead. Come Spring I'll really get to work on a load.

Have to make mention here that Graeme Wright's book "Shooting the British Double Rifle", especially the updated 3rd edition, is (as most here know) an invaluable resource for loading the various BP and Nitro cartridges.

Cheers,
Mike