When I bought my Model 24, .22 Mag/20 Gauge, there were no options - the shotgun was full-choked. That was back around 1963, maybe '64. Options may have been available later. It was originally for my brother, who used it to hunt deer. It did pretty well with Foster slugs as I remember - he got a few deer with it. Now I have it again, but mostly use the shotgun barrel to shoot Punkin balls.
I guess slug shooting depends a lot on the individual gun, but brand of slugs can make a big difference too.