In the first scene, after the fight between the man bowling and the mysterious client, the bowling pins have re-racked, where as before the fight there were pins missing.
(at around 14 mins) The camera focuses on James Wesley's watch. You can see that the watch is a sweep motion, yet the watch ticks once a second. Sweep watches generally tick at least 5-6 times a second.
At around 2:13, when Healy pulls the trigger on his H&K pistol, it is implied ironically by the previous flashback that the firearm "jammed". However, as the round did not fire at all this type of malfunction most likely would be caused by a faulty primer on the cartridge or a light strike by the weapon and would be referred to as a "failure to fire". Alternatively, the pistol could have serious internal issues. In either case, Healy referring to a revolver being less likely to jam is irrelevant, as a revolver is just as capable of suffering from a malfunction due to ammunition failure.