r/canadaguns • u/starw24-ps4 • May 01 '26

Fix my gun SKS Undergassing Fixes?

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I have received an sks that has a barrel which has been cut and crowned down to 18.6”. The owner told me it has been short cycling, which from my research says could be due to either the gas system being loose or more likely due to the dwell time in the barrel now being shorter.

I am going to bring this gun to the range with a bunch of spare parts for a day to start troubleshooting it, and see if I can get it to work. My current fix steps are below, am I missing anything? Do you guys have any tips to help this cycle? 18.6 Sks pictured with a cherrywood stock for attention.

  1. Try it as normal, if it doesn’t work then -

  2. Swap gas tube to second one

  3. Tape front end of gas tube in case of gas loss

  4. Swap long gas pistons

  5. Swap short gas piston and spring

  6. Swap recoil spring

  7. Swap bolt and carrier

  8. Try a detachable mag and new ammo?

Worst case if it still doesn’t run, I may look into either getting a lighter recoil spring or cutting down an extra one to see if that lightens the bolt. Thanks!

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u/PT6A-27 May 01 '26

Generally it’s been said that the SKS comes out of the factory heavily over-gassed. Cutting SKSs down to 18.6” (or even shorter in the United States - not unheard of to see “para” SKSs cut down to 16.5”) is usually a trouble-free affair with no impact to how the rifle cycles. Your gas port could be out of spec, but it’s a pain in the ass to address this as it requires removing the gas block from the barrel. I’d be tempted to investigate the easily replaceable stuff first if you have parts to swap out, and if that doesn’t work out, the gas port is probably your culprit. 

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u/starw24-ps4 May 01 '26

Yeah with my standard 20 inch ones I’ve never had any issues gas wise minus it blowing too much in my face lol.

I wasn’t sure if the paratrooper ones had a different size gas port as those are cut from their factory. Hoping it’s not a port issue, like you said I’ll just bring spare parts from another sks and swap until something cycles. Thanks!

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u/PT6A-27 May 01 '26

There are 16.5” para models that came from the factory at one point (no idea as to whether the gas port is re-sized or not), but you can also find several forum posts of guys who cut their SKSs down. Seems to be a your-mileage-may-vary type of situation - some guys are reporting no issues at all, while I’ve also seen others that have reported similar gas issues to what you’re experiencing, albeit more rarely.