MMP and Harvester both make a variety of sabots for use with different bullets and different bore diameters. You’d probably be better off calling them and asking which sabot they’d recommend with the powder you’re using. FWIW, there is no spec’s on “50” caliber. If you actually measure the actual bore size from different manufacturers, it’s all over the map. Both MMP and Harvester can give you advice on what to try. I’ve talked to both companies in the past and they’ve been very helpful. I don’t know if they still do it, but I’ve gotten samples to try in my various guns. Unless you’re using the correct sabot for your bullet and gun, you’re going to have some problems with accuracy. One other thing: you didn’t say what powder you’re using. Some types require swabbing and cleaning the bore between each shot to get best results. Waiting for barrel cool down is also critical with all sabots. Heat is the enemy of all sabots….warm plastic doesn’t perform well. Properly done, a good muzzle loader (at least an in-line) can produce close to 1moa groups with the right set-up and routine. Good luck