Home Forums Hunting & Shooting AR and Tactical Rifles 6.8 vs. 7.62x39 vs ???

What is the actual SAAMI pressure limit for the 7.62 x 39? Everything I have found lists a Max pressure of 45,000 PSI, some list the Max pressure at 45,000 CUP. The only place I have found a pressure limit of 51K psi is in Quickload.

Ramshot/Accurate list pressures in PSI in their load manuals. They have the x39 running in the upper 30's low 40's in PSI?

Stick said it best, "it's all about the bullet".

over my life I have seen 3 165 grain cup and core 30-06 bullets one from a Hornady Light Magnum load stopped by a simple WT buck. I know a 170 pound deers shoulder and what is behind it will not stop a 62 grain TSX for a fact.

Speer #13, and QL.

The SAAMI pressures for the 7.62x39 are set where they are due to the SKS. The AR or a bolt gun is a whole other critter. Again, like the SAAMI pressure for the .280 Remington/7mmExpress being set at 58k while the .270Win is well over 60k because the .280 was introduced in the 760 semi-automatics.

The 7.62x39 can be SMARTLY throttled forward in either the AR or a boltgun, and if you really want to compare apples/apples with it in an AR with the 6.8, you pretty much have to. Again, just like comparing the .280 vs .270 in a bolt gun.

The Speer #13 lists an average pressure of 50,000 CUP, not PSI. Which equates to approximately 61,000 PSI. This has to be a Misprint.

I agree that the load data for the x39 is anemic and can safely worked up. I disagree that the SAAMI pressure rating is 50K, PSI. It is more like 45K, PSI.

http://www.handloads.com/misc/saami.htm

http://www.leverguns.com/articles/saami_pressures.htm

http://www.lasc.us/SAAMIMaxPressure.htm

Edit. I searched through SAAMI's web site and found this.
7.62 x 39 50,000 CUP.

It also listed it in PSI.
7.62 x 39 45,000 PSI

Bringing the x39 up to and over 50K psi may be fine in bolt actions, but maybe not such a good idea in an AR type rifle.
The x39 and the 6.5 Grendel share the same rim diameter .447. It's my understanding that this large rim diameter is one of the reasons the Grendel has a safe operation pressure rating of 50K psi, while the small rimmed rounds like the 223/5.56 can safely run at 60K psi in an AR.

Who decided the grendel has to stay at 50 to be safe? ANd how was that decision made? I"m not arguing it, just asking.

I have no idea, but I would have to guess it would be Bill Alexander and maybe Arne Brennan.

I got the bolt face info from Mike at DTech, here.
https://www.24hourcampfire.com/ubbth...824506/Re_AR_Pressure_Limits#Post2824506

But there is my point, VA.

You mentioned 174's and 180's reaching .303 Brit performance. So I checked standard .303 Brit specs and I'm saw 2500 fps with 174's and 2570 fps with 180's.

According to Wiki, the Mark VIII round used during WWII was the 175gr pushed at 2525-2900fps.

And has been already established in this thread, 2500fps+ is hard for an AR based 7.62x39 to achieve with much lighter bullets, so I knew it was going to be darn near impossible with 174's and 180's.

So, yeah, I can buy 2200 fps, but that wouldn't really be 303 British.

Standard performance for the .303Brit and a 174 is 2440, from the 25" barrels of a No.1 or No.4. In a No.5, it's 2300ish.

And, what I said was nearly .303 British perfomance/levels. You can easily exceed 2200.

Kind of like saying you can get near .30-06 performance out of a .308, or nearly .308 performance out of a .300 Savage.

All of which is true.

BTW - the MkVIII was a special purpose round. Standard issue was the MkVII, 174 grain ball at 2440. Standard SP hunting rounds are 174s, at 2440. Again, measured from the long barrels of the No.1 and No.4. Knock off about 100 fps for the No.5.

and knowing Bill and Arne, neither would have any business setting a max pressure level. IE not enough knowledge there or testing equipment vs the bolts and pressures. Great folks and I loved doing some of Arne's test firing of the Grendel, but you have to have labs to set levels...

Like I've said before, I've seen more than a few oddball bolt faces in the AR15 guns, but mostly 223 faces. Guess which one I've seen loose a lug? 223....

Jeff;

I'm thinking someone with considerable AR experience ought grab up a 7.62x39 upper and ring it out for a while...

Would probably make one helluva pig killer, eh?

tempting me again eh? Had I access to pigs like I used to, it would be a no brainer...

240 smks subsonic with a can....SMACK

I check a few of my loading manuals, for the 303 Brit with 174gr bullet Hornady listed the highest velocity with 2500fps out of a 25.25 inch barrel. Using QL to reduce the barrel to 16 inches as in the x39 data we get 2219fps.

I mentioned the x39 knocking on the door of .303Brit performance, not reaching it.

Standard .303Brit performance is 2440 for a 174 via a 25" tube. Set the tubes equal, load the same 174 or 180 grain bullet, load the x39 up, and guess what? It's CLOSE to .303Brit performance.

Which, is exactly what I said.

And I agree with you, that is the point of my post.

If this .300 Blackout upper doesn't get better on accuracy, then I may bite on a 7.62x40 barrel from Wilson.

You're right on the barrel length. I didn't think about those Enfields being such telephone poles.

But here we go again comparing hot rodded loads to anemic loads.

I checked Hodgdons on the 7.62x39 and the largest bullet load they show is 150 gr and the max load they show is 2192fps.

Hornady as well shows the max load at 2200fps for the 150 gr 7.62x39 and that again is with a 20" bbl.

So you've adjusted the .303 down to 16" bbl, and then compared it to a 174gr load claim for the 7.62x39 that there is no way in hades is in a 16" bbl.


I'll lay down the gauntlet, fellas. Show me a 7.62x39 load that will fit in an unmodified AR 7.62x39 magazine within SAAMI pressure max, with a 174+ grain bullet in a 16" barrel, that approaches 2200fps, from a legit source and I'll owe each of you a beer.

Edit: Notice I said "approaches" since VA didn't claim it would match it, but "knock on the door". Get within double digit fps and I'll take it.

Where did I say you'd get there with the anemic loads required for the SKS?

Hint: I didn't.

I have no idea WTF your issue is with this one, but damn....

The 7.62x39 IS capable of doing exactly what I said it would do loaded to it's potential IN AN AR or A BOLTGUN.

Why you have a hard-on to modify what I said, or what I said the parameters were to get there, I have no idea.