If the gun was supposedly already a tuned slug gun with the NSA 23gr, why not just shoot what the seller claimed he had it tuned for? These guns are already walking a very fine line when you find something they seem to like and have the gun set for them. Firing random slugs without tuning around them individually is just massive shots in the dark. One other tip is to start with a basically stock gun. Learn what it likes and how it reacts with you tuning it. Then as you mod it with power kits and other fluff, you will see how those mods react to your gun. Sometimes they are steps backwards in ease of tuning for the minuscule gains you get from them. They can make a gun walk an even finer line but it’s not as big of a deal to the guy who knows his gun versus the guy who just was just handed it and told good luck. If the seller is telling the truth and claims the gun was accurate, you already have all the info you need to start from. If what he says doesn’t work, you are back to the no shortcuts way of tuning for slugs like the rest of us. That’s probably why you’re not getting a bunch of responses. Over the years when you see trusted members saying they like a .217 but you have amazing results with a .218 or .216 out of the same barrel, you start to realize you are on your own with YOUR gun.