I've got a rem 870 super mag. Here in michigan we can only use shot at night, so i have a turkey choke and some #4 3 1/2in. My question is during the day i want to use buck shot. in the open areas i have a semi auto 243, but buckshot would be my best bet in the thick swamps. I'm lookin at #4 buck. Anyhow what choke should i use. Do i need to buy a full choke, or will the turkey still work. I think i should buy the full. Any comments

There will be other opinions, but I will speak from military experience. Also, set up some butcher paper and see how your shotgun really prints. Buckshot does best in cylinder bore or impr cylinder at best. Because of shot size, it is not agreeable to shaping in a choke like a tall column of small bird shot. But don't take my word for it. Take it out and see how she shoots. Good hunting.

Use a Mod. choke

As was said by biscuit, you need to pattern your gun as all shotguns are not a like. BUT most likely the 4 buck will pattern better in a more open choke such as cylinder or improved cylinder, possibly modified. The large pellets don't work well through the extra tight chokes, so I highly doubt that a turkey full will throw a very good pattern.

Try a turkey choke. I know some guys will say it won't pattern good but these same guys most likely haven't it.

maybe no choke. just run up and start pumpin lead

I use a 3 inch 12 gauge. I have an extra full choke rated for steel shot and "heavi-shot". I use Heavi-Shot / Dead Coyote, which is "T" shot. This shot is slightly larger than BB and slightly smaller than #4 Buck. Man, this stuff really works out to 55 yards.

Before buying another choke, pattern with what ya got, you might just be surprised with the harder shots that are now available, they just don't deform much any more!
If you aren't happy with the pattern you get, then look at buying something a little more open.