Mike, you would not need to worry about 2 1/2" shells for a Webley 728. They're new enough to be 2 3/4". I never owned one of those, but I did own a 720 (which was made during the same time period, dating from around 1970), and it had factory 3" chambers. It also weighed in the 5 3/4# range, and I figured anyone who shot a 3" shell in that gun had me in the bravery department. Or perhaps the foolish department.