My original thinking was that you should practice with what you carry in terms of recoil, but I have changed that. Your emotions and adrenaline will make an emergency life or death situation completely different to where you probably won't notice a difference in recoil or sound. So long as the your 40 loads are not ultra low recoil loads, you'll be fine to practice with just about any ammo.

The important thing to to is be familiar with the pointing, trigger action, clearing of jams, changing mags and sight picture. It seems 9 times out of 10, you never even see the people in a shootout aim at each other.

I think whatever you can get will be better than not practicing at all.