Svt 40 unlocking too soon

[dark.zero.x]

I have a '41 fin capture svt 40 I got when I was 18, it is hands down my favorite rifle I own, I have shot it a lot. As they years went on I had to replace some parts as they wore out namely a cracked gas block, and corroded piston cup.

Since replacing the gas block ive gone from 75% working to 100% save one failure to feed (repro mag) ive also noticed that the cases are buldging near the rim to about the middle of the case, its not drastic, but enough to not fit into the chamber after firing. Its like the rifle is unlocking too soon before the pressure drops. I used a no go gauge and It did not close. The springs are orginal from the last time the finnish army did work on it as far as I know.

I haven't shot it since I noticed the cases, but I really want it to get back up and running again. I was thinking try new springs, and see how it goes. But if you guys have a better idea please let me know!

 

[barnbwt]

Bulging halfway down the case? Sounds more like a chamber issue (eccentric ream will result in a wider than desired chamber, which a gauge may not detect).

I assume you already played with the adjustable gas block? It'd be interesting to see what your brass looks like when fired with the gas shut off completely.

So stupid that we can't import more of these things; very classy guns (if a bit on the crude side)

TCB

 

[lysanderxiii]

Pictures of said bulged case would confirm the diagnosis....

 

[Onmilo]

Bulging halfway down the case? Sounds more like a chamber issue (eccentric ream will result in a wider than desired chamber, which a gauge may not detect).

I assume you already played with the adjustable gas block? It'd be interesting to see what your brass looks like when fired with the gas shut off completely.

So stupid that we can't import more of these things; very classy guns (if a bit on the crude side)

TCB

I'm also guessing you are using brass case ammunition?
Try some steel case ammunition and drop you gas port size one notch

 

[joem1945]

Try changing the gas port setting.