Frank, you could give it a good cleaning with a bronze brush and then see how deep the corrosion is. If it does not seem too deep I'd try some soft loads ( one 50 grain pellet and a 240-250 grain bullet in a .50 cal. rifle) and see if you get any appreciable plastic fouling from the sabot. A spit patch will get enough of the 777 "crud ring" out to seat another bullet but it usually won't get rid of plastic build up.
Many CVA rifles (maybe all?) were made with relatively soft extruded steel barrels. They have had a lot of issues with barrel bursting which a quick web search would show. That said, I have Winchester branded rifles made in the same factory that have given good service for years.
I'd keep the loads to no more than 100 grains of powder and a 100 grain equivalent of pellets regardless of what CVA claims. Note that Hodgdon, who makes 777 and Pyrodex, specifically states that two 50 grain or one 50 and one 30 grain pellet are the safe maximum. Check the data and warnings at:
http://hodgdon.com/ml-warning.htmlSince Black Powder Industries, who makes and markets the CVA and Winchester Blackpowder products, does not proof test their barrels and won't provide any testing data or state what strength the alloy in their barrels is when asked I'd be very cautious with heavy loads, particularly with heavy bullets. I have always used 240-250 grain Hornady XPTs with MMP sabots in my .50 Cal. Winchester Apex with good results.
777 and Pyrodex pellets are very inn efficient and awfully expensive-around $80 a pound. I prefer the control and cost of loose powder. I'd recommend trying Blackhorn 209 powder. It does not build up the fouling of 777 or Pyrodex and does not require the immediate cleaning of the Hodgdon products and generally gives higher velocities with similar loads.
Good luck
Lance
