Mike,
Although this wouldn't apply if the conversion was done in the US, in the UK many rifles were converted to shotguns when the rules changed back in the 60's (may have the decade wrong - before my time).
Rifles were split off from shotguns in the terms under which they were licenced. For rifles the weapon was licenced, and still is; for shotguns the emphasis lay with the person. ie. one could have as many shotguns as one liked but each rifle had to have a 'reason for ownership'. This is still the case which is why the British rifle enthusiast is rarely a collector - they would need a special licence (or a very understanding local firearms department) to have more than one rifle for any particular purpose.
Therefore rifles without any real purpose were turned into the appropriate gauge shotgun and kept for the children or occasional use round the farm/estate.
This explains the huge number of Rook Rifles converted to 410 shotguns.
Before this kicks off another tirade from some on the horrors of the British firearms legislation, I for one am pretty pleased that every 'old boy' doesn't have access to a rifle in our overcrowded isle.
However, I do regret the trashing of so many lovely old rifles, a terrible shame.
