Get an old bayonet, cut off the spike and modify the mount to accept the bipod, that way no mods to the gun and it comes off easy.
The barrel on a No4 is free floated in the stock. It was designed that way. Be aware that your idea will affect the POI and accuracy of the rifle. For maximum accuracy you want to rest the rifle on the wood stock. Maybe get an F Class bipod with a front rest and lay your No4 on that to shoot?



























