Hi guys, I was able to complete this Cockerill HEAT-T set recently after acquiring the case. What's unusual is that there is a second hole in the base, with a channel running to the outer edge. The inside of this second hole is threaded, much the same as that of the primer in the centre. I know the Cockerill is referred to as a 'low pressure' gun, could this second hole be part of that, a vent/plug possibly? Or is it simply a post-use modification? Training aid possibly? Any input would be most welocme, Many thanks.