Phil,
The McQueens runs all the way through the Imperial meeting, but can realistically be shot any time of the year, range space permitting.
I know the LPSC are shooting it on the sunday afternoon of 4th August, at the same time we are running the S East PR Champs.
Not sure what distance they shoot it at these days, I think it may be 300 as 200 was getting too easy for the boys with wunder-calibres.
I could be wrong though as it's years since I shot it.
We shoot a couple of similar practises in CiV SR, albeit without the castle, with a 200yd Bisley Bullet and 300 yd Wantage.
Both practises involve 10x 3 sec exposures over a 6ft frontage.
At 200 we shoot a Fig 14 window target and at 300 a Fig 12.