This is a $10 Harbor Freight Compression Tester. I own one of them, so I can say it works pretty good,
just be sure you get a 12mm adaptor with your unit as sometimes they have one and sometimes they don't.
vendor and packaging changes according to availability(not complex, very simple to use).
Before I tell myself I have a problem, I personally check to see if I have the problem.Cold cranking compression on a Savage has a very broad service range, from 145 psi to 203 psi.
Technically speaking, I am not remembering anyone who has had to replace any rings apart from a seizure event of some sort which was also perhaps an oil pressure loss event.
Our highest mileage pistons will eventually wear to the point you get noticeable piston slap or piston knock noise at idle and off idle while still running the bike OK compression wise.