No shock nail punch

I recently had to drive some hardened nails into brickwork, the kind that are in cable clips and had to punched them below the surface of some plaster coving. The reason for doing this was the coving was beginning to be unstable after a disturbance following re-roofing (nail guns etc) and it was an easier and cheaper option than replacement.
The trouble was the shock effect on a normal nail punch was painful on the fingers and having almost 100 fixings to deal with something had to be done, also being hardened nails the punch would skid off. I was fortunate in having in stock some 4 x100 mm long HILTI cartridge nails which will go through steel so should hold up well, all was needed was to radius the head and square off the other end and make a free running sleeve to accept them so isolating the shock effect. As this was overhead work some drag was needed to stop the punch from falling out of the sleeve, a simple fix was to cut a groove in the body and a slot into the bore for an O ring, I could have used a wire clip but I was in a hurry and it worked. I did search online for a similar solution but found nothing. This was a quick and dirty fix and only took half an hour on the lathe, there is also a small c/bore in the end to keep centred on the nail head.

Attachment 28180