SKS Still Won't Cycle With Cast

[Farmall]

Trying the Lee 155 TL bullet in my Norinco SKS. I have tried charge weights of 14.5, 15.2 and 15.5, of Alliant 2400, in an attempt to get reliable cycling, but to no avail. At 15.5, the bolt will cycle, but does not come back far enough to exect the empty case, or strip a new one.
The gas system and bolt are all clean and not binding or dragging anywhere, and I'm wondering if perhaps a change in powder is in order. Does anyone have any suggestions here???
The gun is almost new, and has had probably less than 250 rounds through it. Runs flawlessly with jacketed ammo.
Any suggestions will be appreciated.

Andy

[bruce drake]

I used 22gr of IMR 4895 and 24gr of Hodgdon's BLC-2 over that same boolit to good effect and cycling when I owned a Yugo SKS. I use the same load in my bolt action 7.62x39 as well.

You may have already read this thread but do a search for 7.62x39 on this forum and you'll get even more threads on this excellent cartridge.

http://castboolits.gunloads.com/showthread.php?t=13453

Bruce

[missionary5155]

Greetings
You need more pressure.
I have had REAT results using ACC 1680. Itr seems right arpount 16.5 grains my China SKS started being mostly realiable and the Yugo needed 17.. My Yugo had a worn piston that needed a paper clip wrap in the piston groove. I never tried another powder as to many others wrote about GOD results with 1680 and I found it to be the same. That is with the Lee 135 grainer.

[res45]

C. E. Harris
In the SKS start with 11 grs. of #2400 and increase the load gradually until you get reliable function. Do not exceed 15 grains of #2400. You can work similarly within the range of 13-18 grs. of 4227, 16-22 grs. of 4198, 18-24 grs. of RL-7 or just stuff the darned case with all the 4895 it will hold if you are lazy.

[JeffinNZ]

I used to use 23gr W748 under a 180gr J word in my SKS. Cycled perfectly. You have to use a powder/charge that will generate enough residual pressure at the gas port to cycle the action. From memory, the charge of H4227 that would cycle my SKS popped a primer!!! Bad juju that.

[StarMetal]

I'd say all the comments are dead on. I'd like to add that the SKS was designed to operate at a certain pressure with a certain weigh bullet and a selected powder. Fast powder give different pressure peaks then slower powders. It's very noticeable in pistols from shooting the faster powders like Bullseye, Clays, 231 etc, and then switching to something slower. I can notice the difference is recoil and how the slide snaps back on my 1911's. With that said the faster powders may not have the pressure peak just right to work that SKS action fully. The pressure has to at a certain range at that gas port. It was interesting what Jim in NZ had to say about the primer with 4227 and the action not working fully.

[armoredman]

Looking forward to trying my own first cast boolits in a 7.62x39mm, using AA#1680, and the Lee 160 TL boolit.

[res45]

I guess I should consider myself lucky that both my Chinese & Yugo SKS cycle without a hitch with 12.5 grs. of Alliant 2400 and the Lee TL160 gr. GC bullet,brass just drops right at my feet. Now if I use a charge of 14.0 grs. brass ends up 20+ ft. away. I get just a little over 1500+ fps on the chrono with the 12.5 gr. load.

A few years ago before I started casting my own a friend gave me some of his Lee 155 GC bullets,I did a ladder test starting with 18 grs. of Reloader #7 up to 22 grs. even they all cycled with authority but the 22 gr. load shot the most accurately.

[StarMetal]

I've been amazed at how reduce a load will work AR15's in 5.56 caliber. My French MAS 49/56, also being of the direct gas impingement system, also functions on some pretty reduced loads.

Maybe those type of gas systems have more ooomph to them then the piston systems.

[johnly]

Trying the Lee 155 TL bullet in my Norinco SKS. I have tried charge weights of 14.5, 15.2 and 15.5, of Alliant 2400, in an attempt to get reliable cycling, but to no avail. At 15.5, the bolt will cycle, but does not come back far enough to exect the empty case, or strip a new one.
The gas system and bolt are all clean and not binding or dragging anywhere, and I'm wondering if perhaps a change in powder is in order. Does anyone have any suggestions here???
The gun is almost new, and has had probably less than 250 rounds through it. Runs flawlessly with jacketed ammo.
Any suggestions will be appreciated.

Andy

My SAR-1 functions consistantly at 13.0 grains of 2400 with similar weight bullet. As suggested, a slower burning powder should help to increase the port pressure to the point that your action cycles. Most of the SKS rifles I've seen will chuck brass a long ways, so I'm surprised you are having cycling problems. How far does it fling the brass from military ball loads?

John

[fatelvis]

Farmall, what diameter are your TL bullets? I use the Lee Harris designed bullet (non TL design), at .313",and load them over 15 grns 2400 and get positive functioning from my Norinco. Maybe your bullets are a bit undersized for your bore, and you're not getting a good bullet/bore seal, effecting (lowering) port pressure.

[JIMinPHX]

15 grains of 2400 under a Harris design boolit usually gives pretty snappy performance from the action of a Chinese SKS. The Yugo variant often needs 15.5gr before it functions normally, but the Chinese ones usually cycle well with slightly less powder.

Is there any chance that you might have some cosmoline residue in the gas port or something like that? That stuff can sometimes be so hard to clean off that it seems like it's part of the barrel.

[truckmsl]

15 grains of 2400 behind a .314 135 grain boolit cycles my Norinco AK and my buddy's russian SKS flawlessly with very good accuracy for this type of rifle. I would take a hard look at my setup if I was having your problem. I don't think the powder is the problem. Check the gas port orifice in the barrel.

[NickSS]

I have only tried cast boolits in an AK but got good function with both 16 gr of AA 1680 and 20 gr of AA 5744 with the same bullet as you are using.

[Farmall 1066]

OK.....I just noticed that when I posted about this, the forum let me log in w/o putting the 1066 part of my name in....weird.

Bullets are at .312", no detectable leading, or fouling of the gas port or piston. Tried some of these rounds in a buddy's Yugo.....same results. Bolt does not come back enough to cycle.

Think I'll try different powder next.

Andy

[Farmall 1066]

John, this thing flings mil-surp ammo cases into the next township! The recoil spring seems stronger than on my buddy's Yugo, but his has been shot a lot more than mine too.

Also....where are you guys finding load data for this??

Andy

[JIMinPHX]

The Yugo ammo is hotter & the Yugo guns are generally tuned to match. The Yugo guns usually need a snappy powder charge. The others usually don't.

Since the SKS rifles out there are all surplus, there is no telling what someone may have done to them over the years, no matter how clean & pretty they may look. If your Chinese rifle feels like it has a harder spring than a Yugo, that would make me suspicious. I'd change the spring in the Chinese rifle & see what happens. Maybe you can just swap springs with your buddy that has the soft one, as a test.

[RU shooter]

I'm in the same boat as Farmall I tried 2400@15.2 grs today and same results. bolt unlocks but thats it no ejection of the fired case. this was with both the Lee 155 and a 311466 ,Something that might help that I am gonna try is to trim a coil or so off the tappet spring thats under the rear sight housing,I had to do this on another yugo I had that I shortened the barrel to 17" on ,Without this I could'nt even get ball ammo to cycle reliably.

Tim

[TCLouis]

Issue is not peak pressure, but rather the pressure curve/gas volume. The peak pressure is apparently behind the gas port.
I would think AA5744 is the fastest powder that is likely to unlock and function the action completely and doubt it is slow enough, AA1680 is probably more likely.


If one trims the recoil spring they need to remember to replace it when they go back to milsurp ammo.

[plus1hdcp]

I had success at the range today with 12.5 and 13 grains of #2400 behind a Lee 160gr gas checked boolit in a Chinese SKS.

[Lloyd Smale]

I too use 1680 for cast as well as jacketed in the 762x39. 20 grains of it runs a 130 in my ar15.

[Rangefinder]

I've had great success in my Norinco Mak90 using 15 grains H335 pushing a Lee CTL312-160-2R with a finished weight of 173gr with a GC.

Sounds like you need just a little slower powder maybe--burning a little too fast, peaking too soon, and then petering out by the time it's hitting the piston. Plenty of punch to drive the bullet, but not enough residual to shove the bolt all the way back before the bullet clears the muzzle and you loose all operating pressures. The other thing could be just a stiff recoil spring.

[Ole]

Thoroughly clean the gas tube, paying special attention to lead, and check the rod that runs between the gas tube and the charging handle for hardened cosmoline.

I had a similar issue with my Norinco SKS after about 500 lead rounds and it was due to lead fouling building up in the gas tube assembly.

Clean the gas system of all lead and I bet your problem will solve itself.

You'll know when all the lead is out when the piston moves freely the whole length of it's designed travel.

[Ole]

Once you get it clean, i've read if you coat the gas tube with a light film of ATF, it slows the build up of lead. I can't verify this, but i've read it more than one place.

[missionary5155]

Good morning
I think you have a leaking gas piston. With Full Power loads there is enough gas to cycle.. but it is leaking. Does your rifle throw the Factory loaded brass at least 10 feet?
My Yugo would cycle Milspec about 3 feet maybe 2. But cast would open the bolt halfway sometimes or just a bit more.
I wrapped a thick paper clip cut to length around the gas piston groove and fitted it to the gas piston hole.
Now the old Yugo cycles my standard cast load of 18 grains 1680 with the LEE 155 gc boolit as well as our Chicon sks´s.

[plus1hdcp]

Once you get it clean, i've read if you coat the gas tube with a light film of ATF, it slows the build up of lead. I can't verify this, but i've read it more than one place.

Ole - what type of lube are you currently using for the gas tube? The ATF sounds interesting. I only have a handful of brass and a typical session is only about 50-75 rounds so the SKS get a cleaning prior to lead build up being an issue.

[Ole]

Ole - what type of lube are you currently using for the gas tube? The ATF sounds interesting. I only have a handful of brass and a typical session is only about 50-75 rounds so the SKS get a cleaning prior to lead build up being an issue.


I used a little ATF on my gas tube last time I fired it, but I haven't shot it to test lead fouling since.

[JIMinPHX]

I've been using ATF for a while now. It works slightly better than motor oil, but I do still get some lead fouling. I may try Bullplate, now that I have some.

[Rangefinder]

Just for those interested, here is the link to my 7.62x39 load work-up thread over on TFL.

http://thefiringline.com/forums/showthread.php?p=4089436#post4089436

[armoredman]

Thanks! I was wondering if I could use H335 for this boolit. Also have H4895 laying about, anyone every tried that powder?

[djoiner]

I"ve been going through the same thing w my chinese SKS shooting Lee 155 gr boolet. With A2400 it will not cycle reliably. I have tried from 11 gr to 15.5 gr. In no particular order it will hang a case half way out. I've since decided to make this gun shoot paper patch. I'm using the 155gr Lee boolet. I'm shootin it wrapped w/tracing paper at .314. Lee reloading manual gives loading data on 150 gr jacket bullets with H4198 and H4895. With that to go by, I loaded 10 rounds and started with the bottom load data. Starting with 4198, I did one each of 18, 19, 20, 21, 22grs. Using 4895, I did one each of 23, 24, 25, 26, 27grs. loaded w/stripper clip in that order. It cycled every round and over all accuracy was decent w/no leading. 23gr 4895 hit bull and 24 and 25 gr 4895 were close. 18 gr 4198 dead on but 3in low. The rest scattered around. I've loaded 3 rounds of 4198-18gr, and 3 each of 4895- 23, 24, 25grs., but haven't had a chance to shoot them.

I still haven't given up on A2400. Too many people are using it w/ok results. I did both cast and paper patch although that shouldn't matter with cycling.

I'm very excited about shooting paper patch in this simi-auto because I can load to jacketed bullet velocities if I want or need to. I haven't had this gun long, but it shure is a hoot to shoot.

[plumber]

I'm in the same boat with my Yugo SKS. I've tried 14.5 15.0 and 15.5 grains of 2400, all of these loads throw brass over 10 feet in my AK's. I'm using the NOE 314-129 SP. The SKS is spotless clean, and throws factory Hotshot or Wolf so far I don't care to look for them. What to do? More powder? Buy a spare recoil spring and trim it? I don't want to move away from 2400 as I have a lot of it and works my AK's just fine.

[StarMetal]

I'm in the same boat with my Yugo SKS. I've tried 14.5 15.0 and 15.5 grains of 2400, all of these loads throw brass over 10 feet in my AK's. I'm using the NOE 314-129 SP. The SKS is spotless clean, and throws factory Hotshot or Wolf so far I don't care to look for them. What to do? More powder? Buy a spare recoil spring and trim it? I don't want to move away from 2400 as I have a lot of it and works my AK's just fine.

Don't mess with the recoil spring. There is a modification to the cylinder tube. You will notice there are gas bleed off holes in the tube that become open when the piston passes them. Best to buy a spare tube and you modify it.

Go here and read the modification I speak of:

http://castboolits.gunloads.com/showthread.php?t=9042&highlight=sks+gas+tube+modification

[plumber]

After reading all the threads, it seems that gas tube mod is for reducing violent ejection. I'm having the opposite problem, it won't eject at all. I would think that performing that mod would amplify my problem?

I have read that 15.5grain is max on the 155 grain boolits, as I'm using a lighter boolit at 129 grain could I benefit from a heavier charge? The only thing that puzzles me is that my Yugo SKS is the only rifle I'm having issues with.

[JeffinNZ]

Thanks! I was wondering if I could use H335 for this boolit. Also have H4895 laying about, anyone every tried that powder?

I used to shoot 23gr of W748 (very similar to H335) under a 180gr Jword out of my SKS and it cycle fine and shot very well. 1600fps from memory.

[DIRT Farmer]

I have used W748 and as I inhertied about 20 lb of Rx7 that was in rusty cans with an old design 150 PB and the lyman 311-291 170 grn in the guns my sons used. I dont rember the loads but they were bottem end J loads. They diden't lead but the gas system got filthy.

[res45]

If the 2400 isn't working you can try these powders. I use Reloader# 7 for my J bullets and it worked well with cast also.


Ed Harris

You can work similarly within the range of 13-18 grs. of 4227, 16-22 grs. of 4198, 18-24 grs. of RL-7 or just stuff the darned case with all the 4895 it will hold if you are lazy.

[Daryl]

If the 2400 isn't working you can try these powders. I use Reloader# 7 for my J bullets and it worked well with cast also.

This is right on from my experience. My Chinese SKS worked fine with 13.5 of 2400. But, the Yugo would not even at the max of 15 or so. But, follow Harris' suggestion on the RL 7 and my Yugo worked great with all loads from the min to max.

[NickSS]

After reading all the replies I think the issue is that the pressure curve on 2400 is just too quick. By the time the bullet passes the gas port the pressure is too low to cycle the bolt. If I were you I would try something like AA 1680, IMR 4198 or similar speed powder whose pressure curve is longer and reaches peek pressure later in the bore. If the rifle still does not cycle say with 16 gr of AA 1680 or 20 to 21 gr of 4198 then I would look at the gas piston and tube or springs. I have been shooting gas operated rifles for nearly 45 years and most times when they wont eject or short cycle its due to the load not the gun. One thing I have found out is that in a gas gun you need to use a powder similar to the powder used to load the full power loads but just not as much. If you try using a slower powder or a faster powder you generally will have problems like you are experiencing or more violent operation that could cause your gun to wear out faster. I like never use fast powders in a gas gun except for M1 Carbines which were made for that type powder.

[Farmall 1066]

Thanks for all the suggestions. We are in the middle of moving to our new house, so all shooting and reloading / casting stuff is packed up, and I have to get a new reloading room built before I can do anymore with this project.

I'll keep you posted. Probably try 4895, mostly because I'm lazy, but also because I have a good supply on hand. AA 1680 ain't to be had.

Andy

[plumber]

I just tried 24.5 grains of AA1680, still can't get the Yugo SKS to cycle. My Yugo AK throws this load 10 feet away. Tried some wolf ammo and the SKS worked flawlessly. Again, I'm using the NOE 314-129 SP. Any suggestions on a max load? I'm stuck!!

[Freightman]

Have you got the gas on?

[plumber]

LOL!!

Yeah, the gas is on. I tried a couple rounds of wolf after and it cycles like a champ.

I watched the bolt and it jumps back a quarter inch or so.

[acl864]

One of my Russian SKS's will cycle with 15.0 gr. of 2400 the other Russian will not. I tried 18.0 gr. of Reloader 7 (the starting load) in the finicky one and it cycled flawlessly. This is with the Lee TL312-160-2R bullet cast straight WW and water dropped, JPW lube and gas check.

[armoredman]

24.5 grains and it still won't cycle? Somehting odd there. My vz-58 cycles with 18.5-19 grains of AA 1680.
I loaded some testers with H-4895, 27.5 grains, compressed load, will try soon, once I double check I didn't overload them!

[Bloodman14]

2 cc's of H335 behind a Lee 160-R does just fine in my Yugo; drops brass about 8 ft. away and cycles with authority. I did the paper clip trick on the gas valve assy. Works like a champ!

[armoredman]

Decided to check my Lymans 3rd Cast handbook - every oddball caliber you can think of, but not one line for 7.62x39mm.

[JIMinPHX]

I did the paper clip trick on the gas valve assy. Works like a champ!

What is the paper clip trick?

[Rangefinder]

Decided to check my Lymans 3rd Cast handbook - every oddball caliber you can think of, but not one line for 7.62x39mm.

Yup, had the same problem----which is why I did my homework and worked up my own.

Just a suggestion, due to the lack of available data for 7.62x39... Maybe those of us that do cast/load ought to compile a load list of our own on a new thread including molds, alloys, powders, charges, OAL's, rifles they'll feed, etc... Just a thought. There is some out there, including info in Ed's 7.62x39 thread. But I think we could expand this quite a bit.

[armoredman]

I agree, we should add to and expand the database.

[madsenshooter]

What is the paper clip trick?

See post #3.

[madsenshooter]

24.5 grains and it still won't cycle? Somehting odd there. My vz-58 cycles with 18.5-19 grains of AA 1680.
I loaded some testers with H-4895, 27.5 grains, compressed load, will try soon, once I double check I didn't overload them!

28gr with a 150gr j-word, according to Hodgdon's site. 2154fps @39,300CUP Since boolits tend to produce less pressure, even though you have a heavier bullet, you're probably not overloaded. If it won't cycle then, you got a problem somewhere.

[Rangefinder]

I loaded some testers with H-4895, 27.5 grains, compressed load, will try soon, once I double check I didn't overload them!

I'm pretty sure you're not overloaded, considering the load data for IMR4895 (pretty darn close to identical with H-4895) says to stuff the case full and seat your bullet. As stated, if you still can't get cycling, I'd say you have bigger problems---semi-plugged gas port, piston hanging up or loose in the tube allowing blow-by, etc.

[Bloodman14]

JiminPhx, somewhere I saw a blow-by-blow account with pics on how to do the paper-clip trick; basically, you remove the gas tube from your SKS and cut a length of paper clip wire to fit into the groove around the gas tube. This forms a 'gasket' around the gas tube groove, thereby sealing the tube against leakage. The re-assembly is a bit tight, but it works!

[Larry Gibson]

My "go to" load in my SKS (Russian) for the Lee 155 gr bullet is 27 gr H4895 in RP cases with WSR primers. Velocity is 1850 fps with very good accuracy. I tested up through 28 gr H4895 without problems other than it was a compressed load. Using WW or IMI cases and LR primers 25.5 gr of milsurp 4895 runs the same 1850 fps. IMR 4895 takes 26.5 gr to make the 1850 fps.

Larry Gibson

[Larry Gibson]

JiminPhx, somewhere I saw a blow-by-blow account with pics on how to do the paper-clip trick; basically, you remove the gas tube from your SKS and cut a length of paper clip wire to fit into the groove around the gas tube. This forms a 'gasket' around the gas tube groove, thereby sealing the tube against leakage. The re-assembly is a bit tight, but it works!

A single coil from a spring of the correct diameter cut to just snap into the groove works as well if not better because it is higher quality steel.

Larry Gibson

[armoredman]

Or you could try to get a new valve assembly from Brownells or Numrich.
Rangefinder, I don't have an cycling issues, that's the gent with the SKS, my vz-58 cycles just fine, though with the lighter loads won't hold the bol back on the empty 20 round mag - haven't tried them with any other magazines.
Hoping to pick up a new mould in a few days, a 130 grainer...now I may need some Lee 6 cavity mould handles...

[JIMinPHX]

If you are still having trouble cycling the action, have you tried checking the spring chamber on the rear (short) piston rod? Have you checked to see if either piston rod is bent? Does the bolt slide smoothly from front to back when the recoil spring is removed?

[FAsmus]

I bought a Yugoslavian SKS a few years ago and fed it cast bullets.

There was no chance for the action function there at first except with full-power jacketed ~ which I didn't want to use.

The problem was eventually traced to the gas-port bushing, which, as you may know in the Yugo, is switchable from semi-auto to "off" for operation of the grenade-launcher. My gas-port bushing had been reduced in diameter somewhat for some weird reason (it looked like it'd been free-hand ground down with a bench grinder) and it made for a great deal of gas blow-by, which in turn prevented operation with anything less than full-tilt jacketed loads. Take a look at yours!

I bought a replacement bushing and now the rifle functions perfectly with just about any reasonable load at all.

Good afternoon,
Forrest

[lavenatti]

I've been using 18-20 grains of x-terminator behind the Lee 155 grainer in my Chicom SKS and it cycles just fine.

[plumber]

Finally!!! My Yugo SKS cycles with cast!!!

I am using the NOE 314-129SP gas checked over AA1680.

I worked up the load from 24 grains to 26 grains with much aggravation. 22 grains cycles all my other x39 rifles. Then I went up from 26 in one tenth increments, up to 26.5. Still nothing! I went to 26.6 and it functions flawlessly. So I made 50 each 26.5 an 26.6, I rapid fired all 50 10 at a time without a hitch with the 26.6. Then I tried the 26.5 and had to manually operate the bolt for all 50. It's weird how a tenth of a grain makes the difference of nothing and throwing the brass 10 feet!

[rvpilot76]

I would load something a little hotter than that if .1 grains is the difference between function and malfunction. Check the speed and see if you can go hotter. What was the temp when you shot? Colder temps may lead to a malfunction even with your 26.6 load.

Semi-related note: I just loaded and shot the 316299 NOE boolit over 14.5 grains in my IO Inc. AK and function was not flawless. The same boolit over 12 grains of 5744 cycled just fine. The boolit weighs 215 grains. Couldn't chrono that day due to the weather, but I'll get some speeds soon.

Kevin