Keep the muzzle on the BG and use your off hand to take one round at a time from the shell carrier and reload the magazine.

(Notice how a right side mount requires me to place my hand in front of my face. This is a good reason to use left hand mounts for shell carriers.)

Top it off completely, if possible.

Why? Because you never know when the fight may start again and you do not know how many shots may be required to finish the fight. Always keep the gun topped off, if possible.

What if he re-engages?

Answer: Shoot him some more.

Then, when he Stops, scan and reload.

What if I have a failure?

Answer: Fix it.

The Failure Fairy isn't going to drop down to help you. You are on your own and had better be prepared to fix the problem.

The optimum solution to this problem is to sling your shotgun and transition to your handgun.

(This, of course, assumes that you have a handgun, we will cover the other option in a minute.)

Sling the shotgun and transition to the handgun and point it at the last known threat. If he starts fighting, shoot him some more with the handgun.

If there is a lull in the fight, you should retreat to cover and try to get the shotgun back into service. It is the superior weapon and you should try to get it working.

This is why we need a sling. Never lay down the shotgun. Why?

Answer: Because you may need it again and if you can get it working, it is the superior weapon. Also, if you lay it down, the fight may separate you from the shotgun and the BG may find it, fix it, and you are then in a world of hurt.

What if you don't have a handgun?

Answer: Then you had better be quick with fixing that shotgun.