I have been casting and reloading the Lyman 525 slugs for a bit over a year now. To save money I have basically just been using Walmart Field and Target multi-purpose loads, pouring out the lead, casting the lead into the 525 slugs and re-crimping them (fold crimp). I am currently getting ~4" groups at 50 yards.
I think some of the major accuracy problems with this slug and using a shotcup as a sabot are 1. Shredded wad petals and 2. The diameter of the driving bands on the slug. I am an Engineer and have a 3d printer. I was considering increasing the diameter of the front portion of the Lyman 525 slug by 3d printing a cap for the front portion of the slug, out of nylon, which would bring the front driving band up to 0.72 inches (a bit less than bore diameter for safety), a rear truncated cone to fill the cavity with a ball on the end similar to the Truball slug and printing my own wad with a recess for the ball similar to the Truball slug. I would actually just copy the Truball slug wad in a program like Fusion360.
Any thoughts on whether this is a terrible idea or not? Is 0.72 inches too big or too small for the front driving band?