I use the G&P 150 rounders. I have the plum ones but they are also available in "bakelite" and black. I did take each and every one apart to file the edges of the plastic bit that is on the end of the spring that is in contact with the BBs. ZERO misfeeds or jams with KSC or BB Bastard BBs
I also have some of the MAG 100 rounders in plum. A spritz of silicone spray twice a season and they work fine as well.