Hi, Both the Wasps and Webley G.P. are long (since early 2000's) out of production, the Wasps around now only have the tin colour and picture on top in common, just in case you are unaware....They are a totally different pellet, and ''proper'' ones must have ''ELEY'' and a Birmingham postcode on the tin.
Pellets if stored properly, can last for generations without oxidizing, especially in cardboard boxes, so you can still use N.O.S. types no problem (I have shot 100 year old pellets in tests that perform as well as anything available today in vintage guns, but they are highly collectable so I don't do it regularly!).
Back in the early 1900's, British gun companies, especially BSA, could produce guns with tolerances (when needed) in the 10ths of thousands off an inch. Generally air rifle pellets of the late 1800's /early 1900's were dire, as air rifles were little better than toys in many cases, and many were smoothbore, but the advent of the Lincoln rifle, and it's manufacture by a "proper" company, BSA, who also made their identical, but re-badged version, lead to people taking seriously pellet design and manufacture.
I have weighed and measured small batches of very early Adder and BSA waisted pellets, and weight and dimension tolerances / variations were up there with most modern stuff in terms of accuracy!
The Adder and early BSA pellets were expensive in those days compared to other offerings, but even then people did not mind paying more for the best results...We have not evolved in that respect
https://www.flickr.com/photos/312284...57608030264100
ATB, ED