I recently picked up a SVT 40. I cleaned it well prior to first use, although it seems to have been well maintained. Bore pretty decent overall. The first 20 or so rounds functioned flawlessly but as it got warm I had trouble with incomlete extraction of the spent round until the last 2 or 3 wouldn't even unlock. The last round, I had to wait until it cooled to use a soft mallet to extract the spent case. Its not like I was blasting away superfast, but it seemed related to the temperature. The extracted cases showed the striations on the neck from the fluting but but no deformity or ruptures. I was using czech silver tip surplus. I cleaned it throughly again at home but I think this may be a gas pressure problem with insuffiecient pressure to extract a hot, expanded case. Does this sound right? Any thoughts? I don't have a lot of experience with the SVT; I know the gas valve can be adjusted but I'm not sure which way does what on the valve.