My BIL has just bought himself an old semi auto fitted with a poly choke. For those who haven't seen them it is a choke which you adjust by twisting to give various constrictions from Skeet to extra full. Seems perfect for a semi as it takes a moment to change choke, doesn't seem to make it barrel heavy & doesn't seem to have a noticeable down side.
So why do they seem to have faded away?