I use a #20 variable in my Commander, and it seems to work reliably with Factory 230 FMJ to 200 LSWC reloads, and everything in between. I initially used a #20 Conventional spring and it handled the Factory 230 fine, but the lighter 200 LSWC loads gave me a lot of FTF and FTE problems. Someone suggested the variable, and now everything works fine.
If you are planning to shoot just Factory full power loads, then a Conventional spring will do just fine.
If you are planning to shoot assorted weight and power loads, then a Variable spring may be your answer.
That's just my 2¢ worth. Hope it helps you out.
[This message has been edited by hunter_h (edited 11-19-2001).]