I know we have made progress with better seals but I find the best seals to have in a vintage gun is the original leather. They just seem to hold up forever, that’s worth more than a few extra FPS. I’ve been extremely lucky to recently purchase some great old vintage guns. All I’m sure with their original leather seals. Weather warmed up to take my BSA Airsporter MK2 out and give it a go. Guns well over 50 years old just put some SAE 30 ND in when I got it. It’s shooting 550+ still right on original specs. Bought a 1930s Tell 2, still shooting fine after 70 years. I’ve purchased 5 Haenel 28s in the last 2 years, all never needed anything but some oil. Two Webley Straight grips one 90 years old same story. I have a FWB 65 with a modern material stop I had to replace, the original just crumbled out. I know leather can wear out but I just don’t see age being much of an enemy. Don’t have that comfidence with the seal in my Beeman R1?