As Mr. Legg noted there is always that palstic deposit at the entrance to the choke since NOBODY makes a seamless screw-in. Be prepared to clean on a regular basis or suffer some degradation of the pattern quality.
Screw-ins are a complex topic and there are actually many considerations that are usually just blown past. In former times I was quite taken with the idea of twirling chokes as the whim dictated. AS time went by I found that my needs were easily answered by the ones in the gun. And it gave me an obvious excuse to buy more guns. I highly recommend that approach.
WtS
