SKS "lockup".....my fault?

One of the benefits of this forum is that you can admit to mistakes...no shame in that, but I have something that baffles me.

I wanted to try a Lyman 311359 in my SKS. I discovered an unopend 4 lb. metal can of SR-4756 on my shelf and found a suggested load of 17 grains. The boolits were gas checked, sized to .311, coated with Alox twice and loaded with no problems. Out to the range......

Loaded one cartridge, just to see if the bolt would retract fully upon firing and lock. Fired the gun, bolt never moved. Humph. Grabbed the carrier handle and could NOT open the bolt. Finally ended up smacking the handle against the wooden bench smartly and it opened. Case appeared normal. Second round, same thing. Normally you can pull back on the handle and there's a small amount of "play" before the lugs begin to unlock. Not this time...the handle wouldn't budge until struck. All shooting stopped immediately.

This happened with BOTH of my SKS rifles, a Norinco "paratrooper" and a Yugo, both normally good shooters with either surplus or reloads. Now, I can see the powder being too fast would cause function problems (wrong pressure curve) but locking the bolt? What in the world happened here?

Edit: I may have answered my own question. Although I have over 40 years of reloading behind me, this is the first time I've seen actual overpressure signs. I re-examined the fired cases and every one of them has a flattened, cratered primer. On top of that, one primer FELL out of a case while I was examining it. From this I suspect that the load was way too fast (hot) and jacked the pressure up to the point where the case expanded and stayed glued to the chamber walls. I would also suspect that these cases (Winchester) now have enlarged primer pockets and are probably useless. If I had been using a j-word, the results could have been disasterous. Too bad I didn't have my chronograph set up......I bet that little boolit was really moving!

It's a constant learning game and I've learned the following:

1.)I was using a powder that I had never used before. More caution/research should have been called for. This particular can of powder is OLD. The price tag says $13.75! I smelled it immediately upon opening and no laquer smell, but no red dust or signs of deterioration although it could be simply dry.....and changed its burn characterisics.
2.)Never accept someone's load data as gospel...especially off the internet.
3.)Examine the ENTIRE case...I was concerned about possible chamber roughness, never thought to look at the primers.

In short, I made several "newbie" type mistakes and got away with it. So, I think I'll junk these cases and start over. Maybe a nice, soft load of 2400.........

That sounds like a fairly mild load of SR 4759. 19 gr. of SR 4759 gives me 2100 fps with the NOE 130 SP boolit.

I haven't tried SR 4756 in the 7.62X39, but I imagine 17 gr. may be a wee bit too much of a good thing. :roll:

Do you think maybe you confused the two powders? :confused: I'd check the data source again to make sure.

I use both 4756 and 4759 so I re-check at every step of the loading process to make sure I have the right powder for the application at hand.

I'm glad that neither you nor your rifle suffered any damage. Be thankful for the strength of your SKS...I don't think that load would have been so kind to my CZ bolt gun.

Jerry

YOU ARE CORRECT! I just checked and I did read the data incorrectly. Unbelieveable. Well, if nothing else I can expect there's nothing wrong with the powder, just the guy doing the loading. I'll junk the cases (sob) and start again from scratch. Maybe I should attend church a little more regularly too.........:)

3006guns, Glad there was no damage to you or the guns. The SKS is a very strong rifle able to take an occasional bit of abuse.

4756 is about the same as Red Dot in burn rate. For the SKS, something around 10 gr would be my max- which probably wouldn't cycle the action. As said, for 4759, you'd be right on with that charge.

Well, I CAN report an injury though........a big bruise on my forehead from banging it on the wall repeatedly.

Guys, thanks for the information and help. I've crushed and junked the cases and labelled the can "Read the data, stupid!". Meanwhile, I'll try some 2400 loads today if the weather permits.

Hey, .3006guns. Others have confused 4756 and 4759 before. Just glad you're OK and the gun is undamaged.

You might want to check the gas piston shank as well as the piston extension. The gas pressure through the port could have bent one or both.

The Lyman #3 CB shows for the 30 M1 Carbine 6.5 grains of SR-4756 gives 38,100 CUP and 1463 fps which is a MAX load under a 311359 (113 grain GC bullet). In the 30-30 Winchester 11.9 grains of SR-4756 is 37,700 CUP and 1793 fps under a 115 grain, also a MAX load. The carbine is half the case capacity and the 30-30 is 25% larger than of the 7.62x39. Extrapolating between these two values gives a MAX load as 10.1 grains under a 113-115 grain cast GC bullet. Using the same logic with 5.5 and 8.6 grain START loads for the 30M1 and 30-30 respectively, a charge of 7.5 grains of SR-4756 under the 113 grain Lyman 311359 works as a starting point. As said the weapon may not cycle even with a MAX load. I am glad the SKS is a tough weapon as you were probably at 60,000 CUP and maybe higher!

Wineman

I cleaned and checked everything when I got home.....nothing bent, broken or out of whack. God knows why.....it should be!

60,000 cup?!? And I'm one of those guys who prizes very conservative loads in order to go easy on my guns. Fortunately, no harm to the gun or myself, but I think I'll take the rest of the afternoon off..........to work on some conservative data.

Those SKS's are tough, and that's a fact. My Yugo 59/66 survived a double charge of 2400 (wrong dipper). Some minor damage to the boltway right by the breech, and a burn mark on the Tapco mag, but that was it. Fired the first round, and quit for the day!

My mother in law was fond of saying when driving in traffic: " I need to keep my wits about me" Reloading is kind of like traffic: stay alert, don't get distracted with a phone or TV, look both ways and then once again to the right. It never hurts to get a second opinion, or look at a manual one more time. We are all glad you are not injured and your SKS survived.

My family had a piece of land in the Modoc Estates up in your area. My uncle had it and lost it when he stopped paying taxes. My other uncle lived in Fall River Mills for a while in the 1970's.

Wineman

I had a friends do that. He took it to a smith and that guy took 2 months to fix it and probably did something similar. We took it out and it did it again. I think it was the ammo he was using. Not reloads but I don't remember what it was. I just pointed it down range an tapped it carefully with a chunk of wood and it knocked it loose.

SKS bolts drop down into the receiver when they go into battery it's a tilting breechblock design,that is what activates the disconnect to release the trigger to fire the rd. When a fire rd. fails to eject usually cased by cycling issues associated with either leaky gas system or weak ammo or dirty chamber.

The best way to release the bolt is not to beat on the bolt handle,take a rubber mallet or your hand and smack the bolt carrier right where the receiver/dust cover stops this will usually brake the locking mechanism and allow you to extract the rd. easily.

Good tip, although frankly I hope I never have to do it again! I know the Siminov action was patterned after the PTRD anti tank rifle, so the lockup is pretty stout.

I emailed my gunsmith buddy and he called this afternoon. He knows how finicky and safety minded I am when it comes to reloading, so he couldn't resist the opportunity to giggle just a bit. He told me that at least I picked the right rifle to abuse (his words). From his research it seems the Yugoslav SKS variation was built a little tougher than most countries.......not out of pride or quality control, but simply because they loaded their ammo pretty hot. True or not, there's no damage to the gun....or me....so we'll both get a second chance with some normal loads!

Dave Scovill , editor of Handloader wrote that they will not publish data for 4756 or 4759 just for this reason. He also wrote than some of the techs at a powder company did something similar.

Glad you and your rifle survived unscathed, except for the bruise on your head. LOL

There are too many powders with similar names/numbers. There is no excuse for three powders with "clays" in their name IMO.

A little church time is in order!

Good to hear all is well.


Best regards

Three 44s

A kindly gentleman that lives in my area came to me a year or two ago with an SKS that had half a piece of brass stuck in the chamber. The head had separated. I saw several signs of severe overpressure. I suspect that the case may have been double charged.

I made a special extraction tool that fit his chamber exactly & then soaked the action in dry ice until it frosted up before being able to remove the stuck brass. I saw no signs of damage to the actual gun, but the owner promised to have it inspected by an actual gunsmith before firing it again.

Those are very tough rifles.

...glad that you didn't get hurt & thanks for reminding the rest of us to remain careful.