Imar,
You mentioned the word waif. For a young person's first try, I would not use any slugs or any buck no matter how they are described to reduce recoil. There are many light loads for first time target shooters. The easiest to find is AA reduced recoil and velocity loads. Way lighter than that universal stuff that can tire sells. As said, because of the short barrel, extra ear protection is a must. I would avoid the use of a knoxx type stock even though it is convenient to reduce l.o.p. I would look for a youth stock for an 870. Actually I would not encoruage your waif to try your gun til she is accustomed to a more recoil friendly 12 bore. Just like one shot too soon can make a puppy gun shy so it can happen just as quick with a child.
I forgot to mention that she plays football and is used to taking out her brother who outweighs her by 50-60 lbs.
I shot a match this weekend and afterwards she asked me if I'd brought the shotgun. I told her yes. She then asked me if the shells I had were the ones that made the "big flames". I asked her why.
She then told me she had decided she wanted to try the shotgun. I suggested she might want to wait until I went shopping.
Well, she wasn't buying dad's stalling tactic so I proceeded to show her how to tuck the stock under her arm and push the forend forward.
After asking her for the last time if she was sure she wanted to do this I was told to show her how to load the shell.
First round almost knocked her off her feet (I had positoned myself behind her for this very reason). Her safety glasses end up under her nose.
After fixing the glasses her next instruction was to pass 3-4 shells so she could "load" them by herself. After a couple of questions I figured out she wanted to pump the shotgun.
She ended up loading 4 rounds with some help (spring tension gets a little high for her after a couple of rounds) and then proceeded to unload the shotgun at a pepper popper we left out for her to aim at.
4 round of #4 shot later she was grinning from ear to ear. Said shooting from the hip wasn't very accurate and that she wanted to know how to counter the "twisting" of the shotgun when she fired it.
Asked me if they made them shorter so she could hold it better and not be so heavy. Said the stock was kind of weird and asked if I could put the shorter grip thing on (pistol grip) that she saw in my workshop.
Guess I'm going to have to go find those lighter loads so we can practice her instinctive shooting technique.
Suggested a smaller gauge per the advice of others on this forum and she replied no - because it wouldn't be the same. I didn't ask.
L