The commercial lightweight hammer does not seem to be available, anymore. So, I'm considering a DIY job. I only have a drill press and I know I should not reduce the weight below 400grs. Your advice please a] yes or no? b] if yes, where & what size holes ? Any input will be much appreciated.

You might have a time drilling on that hammer, I think they are fairly hard.

Forgetaboutit. The hammer is too hard for conventional HSS drills. The design of the #1 action prevents any significant reduction in lock time by just lightening the hammer. There is significant mass in the hammer strut, spring, and hammer transfer block which you can't reduce.

RAN

Thank you both - it seemed like a good idea at the time !

I have done it often. I use a cobalt 3/16 bit. Holes near the periphery, behind the sear notch.The difference is noticable to me but it could be my imagination. Seems to reduce vertical dispersion somewhat. GD

I have done it also. didn't even try colbalt. went to carbide right off. 3/16 and 1/8 inch drills. as others have said the hammers are harder then woodpecker lips. did it make a difference? not that I could tell but that is what the customer wanted.