Lesson learned-this is no SKS! Although many of the similar looking components are in the same places and the dimensions (except Length) have much in common, the SVT-40 lacks the brutal durability and simplicity of the gas system of the SKS. The cup was corroded to the piston thus no rearward bolt movement upon firing. Anyhow, got that squared away. Shoots pretty darn accurate too. The guy I bought it from really knew how to zero a rifle as I was able to hit clay pigeons at 100 yds with ease.
Now another issue has developed. About every fourth or fifth shot the bolt will "stick" just a centimeter or so short of it's rearward travel. The spent case is still on the bolt face as it hasn't traveled enough to hit the extractor. After removing the spent case, it takes a rather hard forward palm slap to free the bolt which then seems to function just fine. After another five shots or so the problem is repeated.
I am well aware that there is good reason that the SVT did not become a successful and much copied design. In fact I am quite hesitant to continue shooting it. I am debating on whether to resolve this issue at the risk of breaking something or just keep it for it's historical value. I have only used non-corrosive PPU and MFS ammunition. Any experienced advice appreciated.
It's possible to kink the spring if one takes a fit, and shoves it on.