I'm thinking of getting a G20 slide for my G21. I have an Advantage Arms .22 slide for plinking. I thought the 10mm slide would round out the set. I have seen the cost of 10mm ammo; maybe just use it for hunting?
I'm not sure that would work. I think the ejectors are different between the .45 and 10mm and the .45 ejector wouldn't work reliably, possibly at all, on the 10mm. I believe that's the reason that you can do so many conversions on the 20, that you can't do on the 21. If it were just a matter of filling out the hole in the slide, then anything you could do to a 20, you could do to a 21.
I don't know what all the fuss about 10mm pricing is, georgiaarms.com has the cheapest 10mm pricing on the internet. $21.50 for full power virgin brass 10mm? It's great. Underwood ammo also has amazing prices.