I do have rifles, but having to use a shotgun this year for deer. What is the best choke for slugs or OO buck shot. Will a slug hurt a choke?
I have some old 12 and 16 ga. of each.

I wouldn't shoot tighter than a modified choke with either.

Most of the shotguns made to shoot slugs have very little to no choke. Don't know about the buck shot but would guess it is the same.

Generally speaking, a cylinder (no choke) or improved cylinder choke is best for slugs, with a modified cylinder being acceptable. Working the other way seems to be better for buckshot; full, modified, improved. There are fellows over on CastBoolits buying old shotguns with the adjustable chokes so they can tune their slug loads.

The above said, I have shot slugs through full chokes without issue and I have a short, cylinder barrel that shoots buckshot like it was made for it (it was). The best thing you can do is shoot what you have and see how it performs. The greatest obstacle to projectile hunting with shotguns are the sights used and the shooter's lack of range time evaluating ammunition.

I would rather use a slug than a round ball on game. I've shot a lot of critters with .30, .36, .38, .40, .44, .454, and .48 round balls (lever action rifles), and I've never been satisfied with the killing authority of the projectile. A round ball tends to flow around muscles rather than crash through them. If used, even a .69 through .73 round ball in a shotgun, the skeletal structure should be targeted rather than the traditional "vitals."

Thanks all.

Is this something you plan to do in the future and continue?? I would spend the money and get a proper rifled slug barrel for my shotgun and shoot Hornady 12 ga. 300gr SST sabot rounds. I shoot numerous deer every year here in Idaho and it is very accurate out to 200 yards with a Leupold 4X scope.

Just this season.

Blank, wouldn't expect a slug gun being used in Idaho! I found some numbers somewhere on the web that showed more whitetails are taken in our Country by shotguns than centerfire arms. Being in South Texas where rifles are used, it surprised me.

Here is some more reading: https://www.shotgunworld.com/bbs/viewtopic.php?f=118&t=253523

Bottom-line is that any choke will do.