For years the shotgun class instructors at Gunsite indicated preferrence for custom smoothed-up 870's. This was partly because of the perceived advantages of a pump in clearing a dud or a jam, which basically is the same operation as normally chambering a round. Also, shotgun shells, being blunt when loaded, are harder to make feed reliably in a semi-auto; this is for the same reason it is harder to make pistols feed full wadcutters reliably than it is to make them feed ball reliably. Even a Glock isn't typically expected to do that. Gunsite, like any school regularly teaching a particular type of weapon, has an advantage in evaluating the matter because they see hundreds of students go through applyiing different weapon variants to solve the same problems.
It's been awhile since I was out there, but I hear time has at least softened the view of semi-auto shotguns at the school. Semi-auto reliability has apparently been improved. Also, the shoot-offs at the end of each class were showing the semi-auto feed provides some shot-to-shot speed advantage. You may think that's obvious, but one may learn to operate a pump to have a fresh round in place about as fast as you can recover from recoil, so the difference is not nearly as great as you would assume. An expert is able to get about the same speed of aimed fire with both weapons over a short run. Nonetheless, it takes work and practice to get and keep that speed with the pump, and one week of training isn't enough for most students to get all the way there. And face it: most people just don't practice enough to stay in top form.
This leaves the clearing issue. A semi-auto is still more likely to have a feed faliure than a pump, and is therefore more likely to have to be cleared. You do have to let go with one of your hands to clear one, so clearing is a different, slower operation than operating a pump (maybe the pump-semi combination is the exception?). It therefore offers more opportunity for a weapon retention problem to develop, since it takes longer and it is easier to lose the weapon to an assailant while you have only one hand firmly gripping it. A sling may negate some of that disadvantage if you are slung up at the time you enter into the struggle. You have to weigh these potentials in your own mind as well as assessing realistically how much practice you are likely to undertake?
The bottom line is, if you can't purchase the weapon you want, getting the pump's action and trigger smoothed and getting in some speed practice with it isn't a bad choice either.
Nick
