right, just drilling the bore might be the way to go and having checked back through the posts, its thought that the original barrel was not metal. The 19mm bore is big enough if I want to use it as battery holder. Was planning to use a bench drill & jig to get accurate, but realise it will still be tight.
One other thing I was considering was boring it out all the way back to the LED's, taking out the trigger area. This could enable the replacement of a functioning trigger. This may be more trouble than its worth, but just looking at possibilities.
Jim