I have always fancied tuning a bsa lightning, not bad guns for the money!! gas ram might make it pretty special!!
I spent £150 getting an original Lightening tuend up with a Venom spring, Delron washers & had all the internals polished smooth. It shot much better but was about the same a good springer i.e HW97, HW100, AA Prosport etc... Now spend the same on one of those & you can get something really good, with the lock time of a PCP, much reduced recoild and very good accuracy. Getting a Gas Ram is good but it wont improve things a lot. Getting the sears & internals polished up, using hi grade washers, grease etc.. will make much more difference. I am talking about springers used by top end shooters on the HFT circuit, who can outshoot most (if not all) PCP shooters on a good day.
That said a gas ram is cheap & does improve things quite a bit for not a lot. Just watch your fingers & use the right tools (spring tensioners) if you are doing it yourself as lots of people get hurt messing around with springs on airguns; that can be under a lot of preasure & the end results are well known in A&E departments throughout the land.