I have on if .54 and it's a good gun. I converted it to 209 primers a long time ago with the old conversion kit and have had no problems. A buddy has one in .50 and 2 years ago I helped him convert it to 209 primers with one of the new kits. He's had issues with his. Seems to me the older conversion kits were a lot better than the ones they offer now.

For what it is worth I had no issues with it when I used 11 caps. So if the price is right I'd consider buying it.