Nothing wrong with those broken petal-sabots. That is common with those 40/50s. Supposedly, the newer ones don't break off, but outstanding accuracy still occurs with the broken ones. I shot Percisions that broke off for two years. Accuracy remained.

Your accuracy woes can likely be blamed on the 260s. That particular bullet is too thin &long for sub 150 gr.muzzleloader speeds. Cecil Epp (Precision owner) designed that bullet specifically for the Savage smokeless ML-10. You will likely find better accuracy shooting the 180-240 grain offerings in 40/50 -- with the ones around 200-220 grains giving you the best accuracy. Sometimes, adding a ballistic bridge base or a wonderwad between the powder & bullet gets 3" groups touching. So you may want to try one of those options. Cabelas and prbulet.com sell the ballistic bridge bases.