1st off I want to thank the owner of this gun for allowing me to post the modification we made to it.
This is major surgery but not overly complicated. I started with a supplied (known good) used barrel. Origionally the intent was to turn down the entire length to fit inside the sleeve. I opted for using the barrel whole & attaching the cocking link directly to the barrel. The reason for this is anytime you cut material off the outside of a barrel it "relaxes" the metal & enlarges the bore.
There are more than a few critical dimensions that must be correct & work in concert. Of course the barrel is cut off at the breach block-in this case I needed the whole length to accomodate the cocking link. I basically patterned the reciever cuts/threads as the factory did,using the old barrel as a pattern. Once that fit is established I centerlined the barrel & marked the position for the set screw hole.
Being a short blind hole it is imperative to use a blind tap. This can easily be made from a regular tap with carefull grinding. The idea is to mantain full thread depth to the bottom of the hole. The hole is started with a conventional tap & then finished with the blind. Be sure to dress the tip of the cap screw to match the threads. The cocking link was installed with blue loctite & secured.Looks good & will be fine for any normal use it will see.
Test shots went spectacular. This is one of the nicest barrels Ive slugged a pellet through & it works very well in this application. 1st five shot group was one hole. Center bull, kinda hard to see in this photo. The lower bull are the sight in shots.
I have provided some photo's but I need a camera with better macro obviously.
Barrel was taped for protection while testing BTW...