I just bought a 930 from a gunshow for $300 below value, in which it was a no brainer for me. However it's the SPX which doesn't have the choke threads and is a 18.5 inch barrel. I want to use it for waterfowl and would like to control my patterns. I've noticed 500 barrels are a lot cheaper than 930s. Would they fit? I want to get a 24in with threading and found a couple online.