SKS Undergassing Fixes?

[u/starw24-ps4]

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!

[u/No_Win_9797]

You can lighten the spring by sanding the exterior of it, would be slightly more difficult with the length of the spring you’re trying to modify, but placing the spring around a dowel (or anything rigid) so the spring is on the exterior and straight, then placing on end in a drill and sand It down in increments. Good luck on your project, and nice gun!

[u/starw24-ps4 → u/No_Win_9797]

That’s a good suggestion I hadn’t heard before to lighten it, I’ve always just heard cutting or replacing is the option. Will be on my list if the easy fixes don’t work, thanks !

[u/No_Win_9797 → u/starw24-ps4]

There is some east math involved, if you have calibers take a measurement and if I remember correctly it’s somewhere around 30% of total diameter you don’t want to exceed. So maybe start with 10-15% even less.

[u/No_Win_9797 → u/No_Win_9797]

Sks parts are ‘cheap’ though, so going max would only answer your question faster at minimal cost both time and money