Can anyone help me with hammer slap mod?

There are threads about that topic in the quick reference section.

Basically you want to quiet the smack of the hammer hitting the breach/bolt piece by putting a buffer inbetween them. You can groove the breech in a lathe and glue an O-ring on there, or glue a washer made anything else you think might work.

I suggest you read up on what others have tried in the Quick Reference section.