I'm not saying anything.   I sectioned and measured a Grendel (.370) case and a 5.56 (.324)case...

Based on the link giving the case dimensions. The widest point (Shoulder O.D. = .401"-.008) then subtract (Wall Thickness at Shoulder = .016"x2).  That's the best I can do as I don't have a 6.8 case to section.  If it rubs you the wrong way get your dremel out...

Or you can just cut and paste again...

I used the pressure of Hornady factory loads: 50000-51000 per Hornady. (which is what I shoot and my reloads emulate as I have said before)

I'm not trying to "kid" any one, and I'm certainly not trying to convince anyone that 58500psi in the SPC chamber is somehow different than 58500psi in SPCII chamber...  

Even using the base dimension of (Base O.D. = .421"-.008), subtract (Wall Thickness at Base = .032"x2) gives you .357 which is 55000psi = 5503 and 58500psi = 5853, but I know that is not the widest point.

And again, we don't break bolts.
You do...........

Well...

I've bitched up threads, lost some springs, screwed up paint jobs, bent some ocular and objective housings, but I don't seem to recall breaking any bolts.

I'll let you know if I do...

Regarding this, I'm not trying to "kid" any one, and I'm certainly not trying to convince anyone that 58500psi in the SPC chamber is somehow different than 58500psi in SPCII chamber...

None of us are, and neither is he. What we are telling you is that for instance in a 110gr ( not all but several ) , the 58,500psi that is arrived at 2500fps in a SAAMI chamber and worst case barrels, will not be arrived at until 2650-2700fps in a Spec II chamber with all of the other proper specs on the barrel.

In other words,

SAAMI 110gr - 2500fps = x pressure  ( be it 55K or 58,500psi )
Spec II 110gr - 2650-2700fps = x pressure

So that muddy water needs to stop.

The question is, is the 58,500psi safe in regards to bolt thrust, or is it closer to 55kpsi, or what the actual number in PSI is where the bolt thrust safety number is exceeded.

The one thing that seems clear though, is that if you have a number at which the part will break after it reaches that number, or will break after a number of cycles at that number , then when around 100,000  thousand  users of that part are not experiencing damage or breakage, then that number is not being exceeded, or that number is not accurate and is actually higher being more safety was designed into it that thought, or someone's numbers are not being arrived at correctly.


Bolts are not breaking, regardless of what the numbers are, so perhaps there is a mistake in how the numbers are being arrived at, or there was more safety in the design that what we thought.

Water's pretty clear...

58500psi is 58500psi regardless of MV.  That's whats being discussed, not that ammo loaded to 55000psi for a SPCII chamber will spike to 58500+ in a SPC chamber, or opposite hot ammo for the SPC will be lower pressure for the SPCII.

Waters very clear.

Shooting the 6.8SPCII for 7 years at 58,500 does not, has not created any ill effects.
No chamber issues, no bolt issues.
Loads should always be run at the lowest pressure if you can find a combo that does it.
But there is nothing wrong with running to 58,500 to get the performance you are wanting from a particular load if YOUR rifle runs there with no pressure signs.
That's the bottom line of it, that's the intent of the OP.
To show that all the BS about barrel tenon, hoop strength is just that, BS.
Once we had that determined then all this bolt thrust BS started.
But we don't have a problem with bolts, READ NO PROBLEM WITH BOLTS!
Not C158 or 9310, its a moot discussion at this point.

All we have is 2 Grendel guys trying to come up with something, well mostly one G guy.
When there is nothing to come up with.

If I'm a Grendel guy, cause I own a Grendel, then that must make me a 22lr, 9mm, 45acp, .357mag, .223/5.56, .223AI, 6mmx47L, 6.5Creedmoor, 7mmRM, .308Win, 3006, 300WM, 35Rem, 35whelen, 12guage shotgun guy as well...

I load for all of them (besides the 22lr and 12guage), I know what pressure looks like, and I know ar15's don't show it like bolt guns do.  

You started this thread cause you were called out on your other one about pushing pressure levels to get 130's going 2500+fps out of a 6.8 spc 16" gun...

Even XMAN broke a bolt pushing the envelope.... and stated that he was over pressure even though he saw no obvious signs.

For me this was never about this vrs that, it may be your hang up but not mine.  If anything this thread will get people thinking before just blindly following...

ETA 7.62x39, don't reload for it either...

CFE and LEVER are 2 powders that do NOT get to 58500 pushing those speeds.

This thread was started because LR and his "hoop stress, barrel tenon" BS that he has been touting for so long.
When its just not true.
After speaking with Western Powder it was time to put that to rest.

I am following the lead of a bunch of guys that have been loading 6.8 for 7 years.
I am merely reporting their work I have been following and using.

You, and a few others get involved in 6.8 threads all the time, disrupting them, that makes you a G guy, despite what else you shoot.

Wondering how or why some folks seem to think they know more then the powder companies  about whats up ? It's always been presented to me since the early 90's that powder company data was always on the conservative side of what really could be ran safely

So what pressure's do they get to?

Reloading and Pressure
Read away, all these tests were run after the start of this thread.

The 6.5G side in this thread seems to want to scale the pressure of the 6.8 back but if we use bolt thrust as a guide, the 6.5G also gets scaled back and its performance is harmed even more.

I had no idea about the bolt thrust issue with respect to the 6.5G breaking bolts. I did some Googling and there does appear to be a pattern and a problem. Might we venture that the current accepted 6.5G pressure should be scaled back? That would be the logical conclusion if the accepted pressure of the 6.8 was breaking bolts as often as the 6.5G does, no?

Give the man a cigar!

Good info in that thread.  It certainly explains a lot, but hardly helps redeem your claims from your other thread.

anyway, it leaves me curious as to what CFE pressure trace would look like in the Grendel as well as Factor Hornady loads.

Ahh gem,

If one looked at the LEVER load listed there that states "max fill" on the 130 Berger you would see that obviously my load was compressed, as that load is not.
On the 120SST you see a load that is compressed, with LEVER.
I also stated in the other thread I would not share the load because it is rather warm, although not over pressure.
CFE works the same way, at least in the 6.8 case. I have since switched those loads to LEVER.

As the man with the new cigar stated, if any cartridge here in the forum has a pressure problem/bolt breakage problem, its the 6.5G.

....Deflection....  ( your good at that by the way)

Didn't realize XMAN was shooting a Grendel...

I'll file the bolt thing with the rest...
-Doesn't feed
-only good for paper
-need a long barrel
-sucks out of a short barrel
-etc.

In the end a good thread (not this one) resulted with good data.

The one you G guys still have, is the bolt breakage.

As far as X-man, it's not determined yet to the cause of breakage. It is still possible from heat treat issues. , even so, I''l give you that one. You have three.

Yes the G does have more feed issues than the 6.8.
Its due to the fat case in the AR15 magwell, the stack angle is to steep.
That will never change unless single stack G mags were produced.

Bolt breakage in the G is not something that should be filed away but rather folks should be aware of.
Perhaps frequent replacement would help. You guys have done a lot of work but it still is a problem.

The 6.8 does work more efficiently out of a short barrel. Never said the G sucks, just that the 6.8 is more efficient.

The real thing this thread has brought out is the 6.8 is perfectly fine at 58,500 psi.
As it intended to do.

Not addressing most of your post since it's 6.5 vs. 6.8 blah, blah, blah. . . .

Curious, though: Who intended the 6.8 to run at 58,500? Dennison's PowerPoint, for example, announcing the 6.8 SPC to NDIA 2004 says the pressure is 55,000?

Would the same question not be who intended the G to run at 52,000 when Alexander said it should run at was it not 47,000?
Sorry, I should try to stay out of the 6.5 vs. 6.8 blah, blah, blah

We are discussing the SPCII chamber and specs.
So 2004 is not relevant now is it.
Nor is the SAAMI spec chamber.

The fact remains we are not having any problems running the new specs at this level for 7 years running.

Another good thing to come from this thread is a new barrel, 1:10 twist 3R rifling 18in target crown that I think will push the 130gr Berger Classic Hunter to the area of 2650fps with a .497 G1 BC.
Now wouldn't this be sweet if it will do what I think it will?


And perhaps the 130gr Fusion pulls at 2550 to 2575.

It would be a rock solid 400+ yard round on heavy deer even Elk
I have these just under 2500fps now and still a little room in my 16in Bison with LEVER.

It was a simple question. But, uh . . . OK.

I know right, thats enough to make a G man jealous
Sorry all in fun but you did say it brother.

As well I was referring to the intent of the thread my friend.

Was it a simple question? It looked more like an argumentative point camouflaged as a question. And it was responded to in kind, no?

Queries can be used to point out infirmities in an opponent's reasoning and the facts underpinning arguments. The idea that you aren't arguing from an adversarial 6.5 perspective is pretending that the 3,000lb hippo in the room is really just a couch.

Edit: I should point out that I have an ARP custom build (back when Harrison built rifles), a 6.8 "Diamond" rifle with heavy, 16" nitro-carburized, stainless steel barrel. I contemplated selling it to get a 6.5 as a result of the progressive 400+ yard gains but primarily as a result of learning about the broken bolt issue, which indicates, incontrovertibly, that the 6.5 needs to be loaded to lower pressure which would rob away enough velocity to negate any advantage over the 6.8, I'm keeping it.

I find this is making me look harder at the 6.5G and what I am finding is interesting to say the least.
Like this quote:
"Bill Alexander
Operating pressure is 50,000 psi
It is derived from the requirement for a complete durability cycle within the AR weapon system. Determination was from old fashioned fatigue analysis of the design and trials of the weapons. Ultimately the fielded rifles have the biggest effect as the fleet durability is what matters."

Now what does this tell us?
"as the fleet durability is what matters"
Could it be that Bill is saying that during the last 7 years of running the 6.8SPCII at 58500 psi that we have completed a fleet durability test?
Why yes I do believe it does.
As well that since we have no pattern of failed bolts or failed or ringed chambers that the 6.8SPCII has passed a fleet durability test?
Why yes I believe it also does.

Could we also then come to the conclusion that running the 6.5G over 50,000 psi has proven to break bolts and stress the system past its abilities then failing a fleet durability test at over 50,000 psi?
Then could we also say that the very gents that are questioning the work done successfully with the 6.8SPCII are attempting to run their own cartridge "hotrodding" it past what it can do and maintain reliability and are recommending others do so as well?
Yes this also appears to be true.