OK...I've been using knowledge from others on this site and I have Lee 1 oz slug loads I like as well as 9 pellet buckshot loads in shot cups using the Lee .312 ball mold. I have an old but good Remington Slugger with the 18.5" barrel and an 1100 with a 20" tube. Does anyone know what length of magazine extension tube will work with these without extending past the end of the barrels? Any opinions on the most reliable brand to buy? Any advice will be appreciated. GF