Another nice pick up and it sounds like you got into it quite reasonably.
So many of these rifles are overlooked - the general hunting public assuming they are obsolete and ineffective.
I'm sure you will get the best out of it (you have a knack for that) and I applaud you for getting out and working up loads for all of these rifles you are collecting.
As for the ammo, I think I would sell it off since the brass etc. are so easy to come by.
Question though, what is the headstamp on that ammo? Is it like the old Kynoch light cordite with the "L C" stamped on it? If so, I would be more inclined to keep some of it.