PDA

View Full Version : Sks action


xinny
January 13, 2015, 12:28
There's no section on the Sks so I'm hoping that this forum is close enough

I'm tinkering with an idea, and I'm just curious, how strong is the action on an sks? What kind of pressure can it hold up to?

hueyville
January 13, 2015, 22:06
I have pushed beyond reloading manuals.

xinny
January 14, 2015, 01:39
I'm talking 7.62 NATO/.308 winchester levels of pressure

hueyville
January 14, 2015, 05:20
Why? Many objects can withstand significantly higher duty cycle/abuse than original design parameters but in most cases lifespan is shortened and when fail, the inevitable self destruction is likely to be violent. I have some case splitting 7.62x39 rounds developed over the years and in course of developing have not had one of my test SKS's bust. Many were rigged in a rest and trigger pulled with string and watch them run till a case failure caused a stoppage. Once cleared rifle seemed fine and continued to run but I have always tried to stick with Russian built rifles. Dont know if the mettalurgy of a Chinese or other countries build would have held together. I will say its a robust design but the idea of trying to 7.62x51 pressures for long would result in eventual chatastrophic failure. All it takes is having one gun kaboom and it can ruin your entire lifee.

Original secifications for x39 when brought across the pond was based on the pressure testing and design from Finland which had increased the pressure allowed from 45,000 cup to 48,000 cup. Then Ruger got involved when working on cartridge design and didnt want to increase barrel to .310/.311 diameter and reran their data with .308 barrels and sumitted 50,000 cup with maximum single shot of 51,706 maximum cup.

When SAAMI switched form cup to realization psi changes were huge. Expecially if cut a tight chamber in a .308 bore. Almost every country has has some difference in physical chamber/case size, maximum allowable pressure and seems like good ol U.S. has more variation in reamer and case size compared to others. Trend I tend to see is everyone who tests it seems to fudge a little higher on maximum cup, cip or psi the cartridge will take. Problem is which chamber each testing party used, barrel diameter od .308, .310, .311 or even .312. I see wide range in published stats from civilian to military stats.

If you want to wring out an SKS keep upping the load using a machine rest till primers begin piercing. Back off till that stops and you have your limit for that rifle. If those rounds happen to get shoved in different rifle on a different day somebody may regret it though.8 Tons of good data on the subject available if willing to do the research. Currently SAAMI says 42,000 psi max for x39. For the venerable .308 they give 62,000 psi as maximum pressure. Don't think with all the chamber, bore and mettalurgy variations on market that I would risk trying to up the lil x39 another 20,000 psi over SAAMI specs. Now the engineers and such can weigh in and the thrashing begin. Personally, one I hit a point with pressure, I see dimenshing accuracy. Yes I find a few more F.P.S. but group size begins to open proportenately. I suggest each man play within his given comfort zone and if loose a few fingers will definately be sure they found that point where maximum pressure can be obtained. I have blown up rifles. From years of doing so I seldom go any more than 10% above the average maximum charge of three reputible manuals. That can get you blown up so work it all up slow and dont be suprised when things break. I suggest if you need more horsepower, get a car with more room under the hood.

Sagerider
January 14, 2015, 08:02
Hueyville has some very sound advice.
If you want more power get a bigger rifle. Pushing the limits is unwise to say the least. The idea that one rifle may be ok with a hotter loading while another may not is very true indeed.
My own experience has shown me this fact with two rifles both chambered in .17 Remington. The Sako does very well with a particular loading while the Cooper does not. I purchased Remington nickel plated brass for the Cooper and use standard brass for the Sako. Both loadings are within the data listed in multipul manuals and as always some are a little hotter than others. The difference between the two rifles is obvious in that the Sako is an older veteran while the Cooper is a new recruit. I suspect throat erosion in the Sako may have something to do with the difference but have never checked it, bullet jump and so forth.
I keep the loaded rounds separated in their own clearly marked plastic boxes so no mix match will occur. The Sako box is marked for Sako only while the Cooper box is marked Cooper or Sako OK. None of us will be around forever and departure time is uncertain at best. I am thinking of my family and the future as well as myself by segregating these two loads for the same caliber.
Exceeding the loading data on the 7.62 X 39 is asking for trouble in my opinion. There are too many rifles chambered for it other than the SKS and with weaker lockup systems such as the AR rifles. Due to increased bolt thrust from the heavily tapered case and less meat if you will in the bolt locking lugs of the AR to allow for the case head diameter increase your load may disassemble your shooting buddies AR rifle rather abruptly.
Another consideration is the case itself. Different lots of brass, I am assuming you are using brass cases if you are reloading. Different manufactures and all that stuff that goes with it. There are many factors that go into developing loading data that the common man is not familiar with and exceeding that data is taking a very big risk for very little gain. I do hope you stick to the manuals and the load development advice there in and have a happy, safe and enjoyable life for many years to come.

0302
January 14, 2015, 10:50
the fal is basically a large sks.

xinny
January 14, 2015, 17:51
Up here in Canada, SKS's are plentyful and cheap. Unfired new chinese rifles and freshly refurbished Russian rifles are around the $200 mark. Anyways, I digress, I've been toying with the idea of building a sks in 7.62/308. Obviously I'd have to build a new receiver from scratch and would have to modify the bolt face. I was just wondering about the strength of the action itself

Drtrumpet
January 14, 2015, 18:05
Up here in Canada, SKS's are plentyful and cheap. Unfired new chinese rifles and freshly refurbished Russian rifles are around the $200 mark. Anyways, I digress, I've been toying with the idea of building a sks in 7.62/308. Obviously I'd have to build a new receiver from scratch and would have to modify the bolt face. I was just wondering about the strength of the action itself

It would come down to the strength of the area between the locking recess and where the barrel screws in I would think. Then, the strength of the bolt itself.

hueyville
January 14, 2015, 18:39
Will you make an entirely new barrel or rechamber a dedicated SKS barrel? As you lengthen the chamber you push neck and mouth closer to thinner areas of the barrel. The idea of profiling a 308 blank to fit an SKS seems like major effort. Why not find a 7.62x54 combloc design to work from? I have tried many a project with mixed results. If proceed, post progress and make sure disability insurance is paid up in event it goes south. A man could chamber an SKS for 300 win mag if tried hard enough but how much effort and expense will be spent. Many a good idea came from goofey ideas so dont let me talk you out of it if heart is set on it. Just be extremely careful.

I love the little SKS myself for what it is. I have an upgrade/conversion that makes it three times the fighting rifle as most often seen but it is done without changing the cartridge. Increase capacity, fit and function and it becomes a rifle I would not hesitate to defend the last 150 meters between myself and trouble. And with less than 75 dollars investment and four to five hours labor. Add 20 round box magazine, trigger job, recrown and add muzzle brake, refinish after massaging as much slop possible without causing binding issues. A thousanth here and there with the occasional hundredth of fit with some ergonomic improvements and I have a $300 rifle that will run with many guns twice that price.

ActionYobbo
January 15, 2015, 18:42
7.35 carcano
same bolt face

johndoe
January 15, 2015, 19:24
Is the action even long enough to fit a .308?:confused:

TXMoose
January 15, 2015, 21:36
I'd wonder if the extraction would be up to the straighter ( not straight) wall case of the 7.62 x 51 over the heavy tapered x 39 case,beside action length questions

xinny
January 15, 2015, 21:50
I dropped a couple 308 rounds into the mag, and it feeds until it comes time to actually go into the chamber because, y'know, its too big lol

Bubacus
January 16, 2015, 07:12
I know this isn't really using the SKS, but if you would like a semi auto with an interesting action that has a pretty big BOOM, you might give an Egyptian Hakim a try in 8mm. They can be had for about $450 to $500. You can even adapt an MG13 magazine for it as well.

It's the one in the middle:

http://img169.imageshack.us/img169/1245/pb190862sq3.jpg

http://i524.photobucket.com/albums/cc324/cntrailrider/Hakim-After.jpg

xinny
January 16, 2015, 12:59
Hakims run around $800 here in Canada, plus we're limited to 5 round magazines for semi automatics. Also, 8mm mauser is obscenely expensive if you don't reload