FWIW, we are taught to never, ever go to our knee(s) for anything... The lone exception being when restraining an already compliant suspect while they are prone on their belly. It's also worth noting that our partner would be covering you while you did so...
Best bet: End the fight quickly, if you can't, you need more range time... Honestly, with most gunfights happening between 3-20', you should not need to reload if you've done your homework at the range and/or training course...