Side clips are found on many fine live pigeon guns.For example Purdey, Hunt, Boswell. [I have shot 1000,s of rounds through my Boswell without a cut to a finger!}
Side clips were fitted to Pigeon Guns and some magnum guns in order to reinforce the action so as to prevent the the tendancy of the barrels to move side ways in relation to the body of the action.In summary, side clips can be expected on guns designed for use with high pressure cartridges.

Roy Hebbes