I changed one of my TXs to use a magnetic underlever catch - no pressure on the barrel. Didn't see any change in accuracy. Artful-bodger made a no-pressure catch for his 77 too, but I don't recall the effect.

See the thread I started discussing this:
http://www.airgunbbs.com/showthread....ght=underlever

ProSport might be the better platform. But rebarreled with a longer barrel / sleeve.