Converting 40 to 9 - reliable?

[HTOWN stunna]

i would think that if you had problems with it the cause would be the mags or a barrel that needs fitting. this is off note a little but if i can converts my AR to .22lr with a bolt change and not have any problems why wouldn't it work on a pistol?

[Rehabber]

I did the conversion barrel idea last year. Nothing but problems. Take off the slide off and turn it upside down. Put a .40 cal casing under the extractor. Notice there is no side play. Now put a 9mm casing under. That slight amount of side play causes the extractor to release the casing too soon and it lays on the top round in the magazine and stovepipes when the slide tries to feed the chamber. Accuracy was great. Jamming was the problem.