Hmm.. I can relate. I had the same issue with Chinese ammo. 1 out of 30 rounds would do the same. After burning through the Chinese crate, I never had the problem again.
What is your gas setting?
1943 svt? Nice!
Clean the chamber. SVT doesn't function well with dirty chambers and also try adjusting the gas valve
My rule of thumb : Once the SVT is broken in a bit (a few hundred rounds after cleaning out the cosmo to make sure all the kinks have been worked out after sitting in storage for decades), grab a box or two of 54R commercial hunting rounds. They have heavier bullets (usually) but actually less powder behind them (as a safety valve given the near century and a half of rifles out there, in varying conditions, that might be firing them). Set your gas to be able to cycle that ammo, and then you should be good to cycle any surplus you come across, quite vigorously.
The only 54R commercial hunting rounds I have available around here have 203gr of powder in them while the surplus stuff usually has around 150gr (more or less) I believe. I don't plan to go hunting with my SVTs so I'll stick with the milsurp stuff and keep the 54R commercial hunting rounds for my Mosin Nagants.
Thx for the advice though.
That's not the amount of powder in the casing.
The weights on the boxes of ammo are 203gr (grain) SP (Soft Point) Bullet, and 150gr bullet respectively.




























