I would also like to add, and I understand I am being critical of the OP but this is a discussion forum, that one 20 round box or ammo is absolutely in no way shape or form enough to testing functionality and reliability. That is especially true out of a short barreled gun that was originally designed for a different cartridge and using a cartridge not really designed to perform in such a gun. I'm not saying it won't function, but less than three magazines worth is nowhere close to enough testing. I have had and seen lots and lots of guns that have way too many failures to be considered reliable for SD but could sometimes get through a box of 20.
I am not sure what the number is and it is going to be different for everyone. Personally if I had a new Sig 220 or HK 45 or another well established ultra reliable combat .45 and a proven 230 grain JHP like WWB or HST, I could probably live with 7-10 magazines worth of testing. 50 rounds at the very least. VERY LEAST. And that would have to be some extreme situation with shortages or I was robbed of all my guns and money and starting over or something like that. In normal times I shoot hundreds and hundreds or rounds before I deem something reliable enough for SD.