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Replacing The Vepr-12/IZ433 Recoil Spring To Run Birshot

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I have a IZ433 (so basically an Izmash made Vepr-12) and it was having issues running cheap birdshot. The main problem was I had my red dot placed right in the way of the ejecting shells, causing misfeeds. I moved the red dot to the rear of the receiver and that definitely improved my reliability, however I was still experiencing jams or misfeeds every couple of magazines. I polished up the rails, hammer, and the part of the bolt carrier that contacts the rails hoping to get the degree of reliability I wanted using light loads. Now I experience a jam maybe 3-4 times out of about 100 shells. I want to improve the reliability even more, however I have heard horror stories about saiga 12's and veprs that fall apart and start to peen if heavy loads such as buckshot and slugs are fired through them after they have been modified to run light loads. My understanding of the gas system used by the Vepr 12 and IZ433 is that its basically a saiga 12 with the gas all the way open. Is it a good idea to put in a lighter recoil spring (i've seen aftermarket springs available and have read that you can use 1911 recoil springs as well) if I run buckshot, buck & ball, and slugs regularly, or should I have 2 recoil spring setups one for light loads and the other for heavier stuff? Or maybe run one of the progressive 1911 recoil springs to hopefully reduce the wear on the gun with heavier loads?

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It should run cheap walmart birdshot with the factory spring. Are you using Winchester bulk? Most saiga's and veprs don't like it. I had to re-drill the (5) factory holes. I did not open them up larger, but a burr had folded back up into all five holes partially covering them. I don't know if it was the chrome or what. It's a job, but something to "blue-print" before you get too creative

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I swap my front spring to a lighter one for running bulk bird rounds. It reduces the pressure required to unlock the bolt thus allowing it to open more quickly, which results in the bolt opening while more pressure is in the barrel.. And yes you want the firmer spring in there for the heavy loads. If I was going to run nothing but high pressure loads I would probably install firmer than factory springs front and back.


For reference the stock spring is roughly a 16 lb 1911 recoil spring.. You likely would not want to go more than a few pounds in either direction.

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Thanks for the replies, @ Wagnikov, now it seems like it runs everything fairly well except the winchester and the federal, but I've had a hard time finding ANY shotgun, semi, pump, or even a couple break opens all have had issues reliably running the winchester crap. @ csspecs, thanks for the info, good to know what the OEM spring poundage is so I know where to start experimenting. It sounds like I might wanna buy a second guide rod and heavier recoil springs for when i'm hunting coyotes, crows, badgers, etc. and will be shooting buckshot and slugs, and I might wanna buy a lighter front spring on my current guide rod to get my gun to run the light bird loads reliably enough for 3 gunning. Do I need to worry about wear and tear on the shotgun if I run the lighter spring for 3 gunning and put a couple slugs or buckshot through it at the match?

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