r/canadaguns • u/starw24-ps4 • May 01 '26
Fix my gun SKS Undergassing Fixes?
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.
Try it as normal, if it doesn’t work then -
Swap gas tube to second one
Tape front end of gas tube in case of gas loss
Swap long gas pistons
Swap short gas piston and spring
Swap recoil spring
Swap bolt and carrier
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!
11
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.
1
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!
2
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.
3
u/therowdyirishman May 01 '26
You seem like quite a thorough gent, so hopefully this isn't irrelevant advice due to you already taking these measures. I would start by doing a through inspection of the gas system. Check to insure the gas port isn't obstructed by heavy fouling. Check out the gas tube to see if heavy fouling or corrosion are restricting movement of the primary piston. Check the same for the short piston and ensure the retention lever is in the correct position. After that I'd give the bolt and guide rails a look to check for wear that indicates an unhealthy amount of friction. Lastly I'd ensure the recoil spring is installed in the correct orientation.
The SKS tends to be quite reliable and receives ample gas. Given this I'm leaning towards the prior owner being a bozo rather than it being a genuine dwell time issue. If I were you I'd try all of the above prior to investing in spare parts. Good luck and give us an update with what you learn after range testing. You can also try posting on r/SKS if you wish.
1
u/starw24-ps4 May 01 '26
Thank you for the reply sir! After the comments on here I’m going to give the gas port a second look, I just eyeballed it and guessed it was fine since I didn’t see anything. Will be giving it a once over cleaning.
Spare parts wise I have another sks so they’re easy to swap in a few seconds, but yeah I’ll give those tips a shot before I start gutting the old girl. Thank you!
2
u/No_Win_9797 May 01 '26
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!
2
u/starw24-ps4 May 01 '26
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 !
2
u/No_Win_9797 May 01 '26
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.
2
u/No_Win_9797 May 01 '26
Sks parts are ‘cheap’ though, so going max would only answer your question faster at minimal cost both time and money
2
u/ThePoeticJester May 01 '26
I think TNA or another gunshop started making newly made gas pistons, maybe the tighter fit there might help? Otherwise you could open the gas port slightly more (hell it'll errode over use to be more open lol) could try stripping it all down and polishing all contact surfaces along the gas system, maybe less friction would help
2
u/starw24-ps4 May 01 '26
Yeah the gas mating surfaces is where I was worried, this gun is a mix and match of different factories so there is a small gap in the gas tube where it attaches to the port.
Will polish before I head out thank you!
2
u/AresV92 May 01 '26
Just to be safe if all else fails before you sell it or relegate it to a parts gun see if you can run a bronze pipe cleaner or wire through the gas port. Unlikely, but could be fouling restricting gas flow.
2
u/MourningWood1942 May 02 '26
I remember seeing something TNA has for sale about that but I can’t remember exactly
1
u/starw24-ps4 May 01 '26
Didn’t think to clear that out first since to my eye it looks clear, but it could be something I can’t see easily. Thank you I’ll try that!
1
u/milanskiv May 02 '26
It's not the barrel length that's the problem. You are likely losing gas somewhere (which would be obvious when shooting) or your piston is fucked/dirty.
2
u/starw24-ps4 May 02 '26
Yeah I got this as a barelled receiver for 50 bucks so im guessing his parts were messed up somehow. My spare parts are all clean with a low round count so im hoping she runs next weekend
37
u/siming_z May 01 '26
Can I just admire how rad the poster is?? OP where did you get this stuff and do they have a Toronto variant?