Too cut or not too cut, that is the ?

[NSP64]

I have a yugo sks that cycles fine with Com-bloc ammo but will not with cast reloads. I am using a 180gr GC .313 boolit that shoots good from it but will not cycle the action. I have used 2400 and 4227 in progressive loadings up until I get hard to extract cases (with flattened/flowing primers) I am using Winchester brass/LR primers getting velocities in the 1700 fps Range. The action acts like it is partialy cycling but not far enough to eject. then the next .5gr increase will stick the case I was thinking with the gas rod spring/hammer spring/recoil spring that maybe there was just too much spring? should I cut/trim the recoil spring?

[felix]

Try slowing the powder down before modifying the gun. Try RL7/WW680. ... felix

[badgeredd]

I totally agree with Felix. I have not yey loaded cast for my SKS but I did load a 150 gr. jacketed bullet and found that RL7 gave me better cycling and improved accuracy. Also you might want to super clean the gas cylinder and piston. Often old gunk gums up the works. SKSs are by nature very forgiving but I have found 2 guns that friends have had problems with that had a bit of crude slowing the piston. Good luck.

[Junior1942]

My YUGO SKS shoots the GB 311041 just fine to 1700 fps with Surplus 4895. I get 100% action function and very good accuracy. You need to change to a slower powder like Felix said.

[NSP64]

I may have solved problem. I think I had the recoil spring in backwards Checked online for disassemble/reassemble instructions and they said to install curly q of spring assembly in first. So, I installed it both ways and checked the force required to cock bolt back to hold open. Correctly installed 26lbs, backwards 32lbs Ill try loads tomorrow and if that doesn't do the trick I'll try some slower powder.

P.S. I disassembled after shooting com-bloc ammo then reassmbled(backwards)

[NSP64]

Went to range with springs installed correctly, 180 gr GC boolits over 15.5 gr 4227(1650 fps measured). First round ejected empty but would not lock it open. Next 4 rounds didn't cycle action I was wondering if maybe taking the spring off of the rear operating rod would be enough to allow it to cycle? My pull 'test' did not include the weight of the operating rod spring.
Also switched from LLA to javalina lube and bore came out clean

[35remington]

newsmoke......

Change the powder. The fellas here aren't leading you wrong.

RL7 and H4895 cycle the gun every time with loads three quarters to full power.

[Larry Gibson]

Newsmokepole64

Advise against cutting the spring or taking it out. As already advised; switch to a slower powder. 4895 will work quite well for what you want.

Larry Gibson

[Jeffreytooker]

Newsmokepole64

Advise against cutting the spring or taking it out. As already advised; switch to a slower powder. 4895 will work quite well for what you want.

Larry Gibson

NSP:

I ran some Quickload numbers for 7.62 X 39 with 19" barrel for a velocity of 1700 fps 180 gr boolit. I checked the pressure curves at 6" down the barrel. I did not check the gas port distance or barrel length on my SKS. The numbers are still representative.

Powder Charge Pmax Distance P@6"
2400 14.9 32.6K ~.75" 11927 psi
4227 17.9 29.24K ~1" 12413 psi
4895 24.3 27K ~1" 13020 psi

As you can see 4895 has better than 1000# more preaaure than 2400 at 6". Also it is a slower burning powder so its pressure curve is not falling as fast after the gas port is reached. This keeps more pressure on the op rod. Try your SKS without the op rod, as a pull bolt rifle. It works well.

Jeffrey Tooker
Paynes Ck Ca.

[NSP64]

jefferytooker,
Can you run the program to see what the press is at 12" down the barrel? I have a yugo sks with a 21" barrel. Thanks Kyle

NSP:

I ran some Quickload numbers for 7.62 X 39 with 19" barrel for a velocity of 1700 fps 180 gr boolit. I checked the pressure curves at 6" down the barrel. I did not check the gas port distance or barrel length on my SKS. The numbers are still representative.

Powder Charge Pmax Distance P@6"
2400 14.9 32.6K ~.75" 11927 psi
4227 17.9 29.24K ~1" 12413 psi
4895 24.3 27K ~1" 13020 psi

As you can see 4895 has better than 1000# more preaaure than 2400 at 6". Also it is a slower burning powder so its pressure curve is not falling as fast after the gas port is reached. This keeps more pressure on the op rod. Try your SKS without the op rod, as a pull bolt rifle. It works well.

Jeffrey Tooker
Paynes Ck Ca.

[Jeffreytooker]

jefferytooker,
Can you run the program to see what the press is at 12" down the barrel? I have a yugo sks with a 21" barrel. Thanks Kyle

Kyle:
I ran some Quickload numbers for 7.62 X 39 with 21" barrel for a velocity of 1700 fps 180 gr boolit. I checked the pressure curves at 12" down the barrel.
Powder Charge Pmax Distance P@12"
2400 14.6 31240 .96" 5419 psi
4227 17.5 27598 .99" 6191 psi
4895 23.7 25170 .84 7102 psi

Besides operating the action, I think 25Kpsi is about max alloy pressure for quenched WW.

Jeffrey Tooker
Paynes Ck Ca.

[NSP64]

O.K. I drove 100 miles round trip to get some IMR 4895 now how much to use? I'll start on a sliding scale 20.0-22.0 in 0.5 amounts.

[NSP64]

Imr 4895 did the trick. 20.0 ejected brass w/n lock open, 20.5-21.0 ejected and locked primer not reseated,21.5-22.0 looks to be right on for function, now to work on loads for accuracy. Thanks everyone for not letting me cut the spring.
P.S. 1550fps