Slugs are truely accurate to ABOUT 150 yds. Shoot reall well at 100. Beyond 150 yds, it is either the shooter, or luck. Shooting a deer with a slug at 300 yds means you had lady luck on your side. Can't brag about the type of gun or the best slug on that one. Just say you got lucky.
Although I have found that 20's shoot a lot better than 12's. They shoot flatter with higher velocities, and can shoot a little farther as well.
A slug that ya'll should try if you have a rifled barrel is the newish remington buckhammer. I shot those through my 20 guage 1187 this year and I loved em. I gave my buck a texas heart shot and had it pass through, which is impressive for a slug. They are all about weight retention and penetration. They hardly expand at all.
Another nice thing about them is that they are a heavy slug. I hate how most slugs are so light, especially the 20's weighing in at about 5/8-7/8 ounce. These buckhammers are one ouncers in 20 ga and up to 1 1/4 in 12 guage. It is impressive to have a one ounce 20 ga saboted slug becuase a 20 ga foster slug is only 7/8 ounce. Also, the sabot is at the bottom of the slug instead of around it. (for you muzzleloader hunters, it is similar to a powerbelt bullet) This offers a MUCH bigger hole, so it really does not matter that the bullet does not expand.
Remington shot a 100 shot group at the factory with the 20 ga's and it grouped 3.5 inches. Yes, you read that right. That is UNREAL for slugs.
Give em a try- they are sure to please!