I used to be a half owner of a Corbin press like that. Back then about 13 years ago we couldn't get slugs to work in our FT rifles, the shape of the slug we asked Corbin to make dies for, the diameter, and weights, wasn't working with our barrels and the twist rates in them. To get things working would have been a bunch more trial and error, something I wasn't interested in pursuing for more than just the financial aspect which included buying more expensive dies, punches, and barrels. My friend and I did some trading and I was out of the swaging business. Believe me when I say that getting everything right could cost you thousands of dollars and many many hours of time to get a satisfactory outcome! That being said things are probably more easy to figure out now than back then as far as small caliber slugs in airguns because back then some of the reason for failure were mysterious.
Just the last few months I started swaging again but using the entire system ready to go from my GS/Thomas Rifles and everything all figured out already for one gun - a match barrel with proper twist, swage die, sizer die, slug ejector tool. Then bought an arbor press, lead wire, and boy the outcome is sweet! I couldn't be happier with all of it including the performance of the slugs and corresponding precision of gun and ammo!
I have another friend that owns a Corbin press which he seldom uses to make 44 cal lead bullets for his lever gun, he mentioned selling it last year. I might just buy it from him if he wants to sell it so I can experiment with 6mm slugs. This time around I'm more familiar with barrel twists and proper fit of slug to barrel so....