They are soft and will not be bothered by your modified choke. Accurate? Yes, they can be. Back in the 80's all I had was an older 870/modified choke 28" barrel with a rib. We had a slug shoot coming up at our local club, 25, 50 and 75 yards all fired standing at about an 8"x10" plate. I stopped by a lgs and he had some nylon clamp on rifle sights that attached to the rib. I've no idea if they are even available anymore and I've no idea what happened to mine. I think I may have given them away to someone.
In that shoot were a number of scoped shotguns and even a scoped bolt action Marlin 12 gauge a gunsmith had modified. The old 870 modified out-shot them all and even aggravated a few. It's been too many years ago to remember how tight my practice groups were, but there was plenty of practical accuracy.
You will be fine if you want to shoot them out of your 870. They were designed to be shot from all chokes back in the day before all the rifled barrels became popular. I would just refrain from shooting them in a rifled barrel. I'd worry about the soft lead getting in the rifling but that's all the harm it might do to the best of my knowledge.
Last edited by grizzly 2; 03-18-2020 at 04:13 PM.