Wow, that's quite a story. Sorry to hear about the grief and loss of a gun, but being the king of odd occurrances like I am, I understand.
The slow vs. fast powder theory is interesting. I had never really thought of it like that before, but it all makes good sense. On a semiauto, the timing is everything.
The whole reason I got the 1100 was because I was looking for the perfect, one gun fits all applications- shotgun. The one size-fits-all shotgun hunts, defends the home, defends the farm, plinks, and fires everything from light target loads to 3" slugs. Since the 1100 is only chambered for 2 3/4", it failed the test. There have been times in the envelope of "farm defense" that I could have better completed my task with 3" Buckshot loads.
The 1100 is so much fun shooting informal clays, and so comfortable, I have no regrets getting it. I can truly shoot it all day long.
As far as 3" shells go, they will let you know if your gun fits you, if your shooting position is right, and much more. Here's the "Maxi" 870
Looks a lot like the 1100, doesn't it? That 870 is heavy. It is heavier loaded. It fits me, it is balanced, and I can shoot 3" shells, including slugs. The gun is too heavy to carry all day squirrel or rabbit hunting.
Along the same lines, I have been working on handloaded shells for vermin. The shells easily fall into the "turkey load" category- heavy shot payloads, lots of powder. I'm using these shells in single shot shotguns. I came across a load that used 1 3/8oz shot, a good dose of Blue Dot, but required a 3" hull. All the other shells I was loading were 2 3/4". The chamber pressure, shot payload, and everything else that effects recoil was similar in these 3" compared to the 2 3/4", so I thought I'd give them a try.
All I can say is WOW!
Here's the videos
www.2guntom.com/454/video/NEF3in.aviwww.2guntom.com/454/video/NEF3inZoom.aviThat's an NEF Modified choke 12ga. You can see that I'm not a thick guy either. I added a Sims slip-on pad which makes the gun longer so it fits me better. It also dampens recoil dramtically. I wasn't hurt, bruised or sore after I fired those. Remember this is a light gun, at least 3lbs lighter than my maxi 870, maybe lighter. The reason, I suspect, that the recoil was so profound, is that the chamber is a tad short; the shells aren't opening up all the way, pressure spike, and WOW!
If you can make the gun fit you, 3" isn't so intimidating. At least that's my theory that I adhere too.