The solid body action is stronger because there is no need to cut slots in the bar of the action to clear the main springs as required on bar action side locks. This increase the strength of the action. Charles Lancaster used back action sidelocks on his 12/20 gun. This undoubtedly allowed him to reduce the weight of the gun without compromising the strength of the action.
I have a copy of the Midland Gun company catalogue of circa 1890
This catalogue provides illustrations of their back action lock.
As stated by lapogus, they are exactly the same design as those fitted to the Grove gun.In this catalogue the gun that most closely resembles the Grove gun is their "Demon" Gun which at that time sold for 5 pounds stirling.
Last edited by Roy Hebbes; 06/30/09 11:32 PM.