This boring sequence right barrel choked,left barrel open bored is sometimes found on guns made in the UK intended for driven grouse shooting. In driven grouse shooting the the first bird shot at is most distant. The second bird shot at is closer to the gun hence The reverse boring.
The reason for the reversal in boring is thought to be that some sportsmen used to shooting flushed game rising close in, always using guns bored open in the right barrel and choke in the left barrel could not, in the heat of the moment, when grouse shooting, automatically switch their barrel selection. Thus distant birds were missed and close in birds mangled!
