They were still using the box the last time I competed, the other check is the minimum trigger pull of 500 grams, but I don't think they really study how each pistol functions.
I suppose it's going to be down to individual inspectors as to whether they think it qualifies. It might be worth studying the rules to see if there is anything about multi-shot pistols in single shot competitions, and if there are any exclusions.

You might just end up being forced to buy another pistol...