While ammo still is placed in magazine (half-empty) and you're performing quick reload (2x R) then slide pulls back automatically and full reload animation plays. Happened on insurgent side with Browning HP

It happens with rifles too, tho inconsistently. Sometimes if I R+R with rounds left, the guy does a simple quick reload. Other times he needlessly runs the action, ejecting a live round from the chamber and wasting a bunch of time.

Given that this seems to be about 50% of the time (I haven't identified any pattern yet), it almost defeats the point of using R+R, which is sad given that the improved reload mechanics are one of the best things about this game's mechanics.