Lloyd,
Use it and enjoy it, that is what it was built for and I am sure your friend would want you to.
I have found with mine that the FPSN 86gr Remington bullets for the .25-20 group well even though they are being pushed at about double their design speed.
I have noticed however that on paper targets they leave a swirl of lead vapour around the bullet hole. And on a hot day from a warm barrel one turned into a puff of smoke about 50 yards down range.
They should work well on varmints.
I did use one once (and I concede it was not the best of ideas) to cull a Roebuck in a very small field where I was anxious to avoid an exit wound and any risk of over travel.
It did the job, but to my surprise chopped a one inch hole out through the far rib as it exited into a safe background.