I love mine.
The J.C. Higgins Model 50 uses a top of the line FN Belgian Mauser action and a chrome lined barrel made by High Standard. I don't know the twist but I can tell you from experience my 30-06 shoots bullets from 150 to 220 grains very accurately.
It has an unusual trigger in that the trigger mechanism is in the trigger guard and the sear is on the action. Use great restraint if you decide to stone the trigger surfaces; if you remove just a tiny amount of material, the trigger geometry is such that the cocking piece will move forward enough to make it difficult to engage the safety. This condition is fixable, but is better avoided.
I can't tell what scope bases you have now, but most standard Mauser bases will fit. You will need a 30-06 length scope or extension bases if you use a shorter scope.
The FN commercial Mauser action is one of the finest rifle actions ever made. The barrel is uncommonly accurate and resists corrosion. They are terrific guns.
I have shot many many hunderds of hand loads in mine and just love it. Enjoy it's a great under appreated rifle with quality fit and finish you just don't find in todays production rifles.