for the second shot.
In preparation for shooting at a "true double" Sporting Clays pair, I would step into the shooting cage with the 870 empty, on safe, then turn it upside down and put 2 shells into the magazine. Then, I would turn the 870 upright, without tilt, push the magazine release in, and shuck the first round from the magazine into the chamber, with 100 % good function. Then I would go to high ready, click the safety into the "fire" position, and call "pull".
"True pair" comes out, I track and fire at first clay, then, keeping the butt pressed into my shoulder, try to rack the action - resulting in 100% ejection of first, fired, round, but only about 50% seating of 2nd round into chamber. Sometimes, after FTF of 2nd round, I would "double shuck", and succeed in chambering the 2nd round, and firing at the second clay, usually at about the time (or a fraction of a second after) it hit the ground.
At the end of the shoot, I had 14 unfired shells. I'm guessing I had 8 or 10 "double shucked", but fired 2nd rounds.
Needless to say, I "won" low scorer of the day prize - a new Zebco 33 rod and reel. I think they were saying that if I expected to put any meat on the table, I would have a better chance at fish than fowl.
Yet, most dove seasons, I can usually get my 15 bird limit with one box (25) of shells.
Using my 12 ga 870 Wingmaster. I decided not to use the 12 ga for Sporting Clays because I didn't want to bruise my shoulder with 100 rounds fired. I had already been shooting rifled slugs with the 12 ga, in preparation for deer season, and had some minor bruising as a result. So, I used my 20 ga, for Sporting Clays, not realizing that it was going to be a problem.