I dont know much(anything*) about this stuff but just wondering what does the higher pressures offer? does it make the projectile faster offering better accuracy or what?
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I dont know much(anything*) about this stuff but just wondering what does the higher pressures offer? does it make the projectile faster offering better accuracy or what?
Is pressure signs mean like the neck splitting? When I got my .308 it came with a bunch of homeloads a few dont chamber and then a few get spilt necks when I do shoot, but the ones have shot group have good grouping and they knock the shot out of deer. idk why some dont fit, I have been told it could be because the were shot through another rifle first???
Wooo - hold up - noones running 88k
If barrel life is an issue when you're poking $1.50 worth of powder and $4-5 pills down the tube, with $4k of scope on top and a $6k range finder sitting beside you, then I think you maybe in the wrong game.
How can a strain gauge be used to determine its safe?
Lets say in a moment of fantasy, that the pressure is 100% correct, you have a magic number of what that pressure is in the fired case- now what?
You realise that if you have to use a FL sizing die or any die, then the brass has past its elastic limit and yielded? this happens with almost EVERY rifle caliber from the last 100 or so years.
You would agree that if you can fire a case 5 times without FL sizing, that you are below the yield point of the brass and operating within its elastic limit?
But Spanners if this brass acts the same as all brass in all calibers has done for the last 100 years then why is it safer to run to a much higher pressure?
Yes but how far bellow you don't know. You also don't know at what point you will start damaging the action. This is what I keep trying to say, but all you can say is its not failing YET!
In Kirby's example they didn't reach the elastic limit of the brass until the action was damaged.
is there not a point where the pressure it too great that the steel used for the barrel / action loses its elasticity?
ie when the strain is beyond the threshold capacity of metal that it’s molecular or the atomic structure changes bringing a sort of deformity in the structure of the metal weakening/fracturing it?
I have read somewhere that this another reason for some of the pressure limits.
Spanner if you need to full length size every time you fire the case it just proves you load to hot. What Kirby clearly says is that the hard brass like Lapua, Jamison ect will not show pressure signs until you are well into dangerous teritory, in this case it set back the action lugs in a big way before the brass showed signs of pressure. Now are you saying Kirby is wrong and this can't happen because you say so?
Ok, so my 20 tactical brass had been fired 5 times, never been full length sized but started dropping primers... I have since reduced the load, still haven't full length sized. How does that fit into this argument? 3 other rifles I know of that have been chambered using the same reamer and the same barrel and factory Lapua brass, neck turned the same as mine won't hold a primer for 1 firing at the load I had been running initially with no issues (approx 2k rounds fired). How does that fit into this argument?
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FYI
Barnard P-Chey is made of 4340 hardened to 38Rockwell C
Yield strength of ~165,000 psi
Yeah but dropping primers is a brass pressure issue too... enlarged primers pockets...
I have a hard job believing that there were no other signs in the Kirby example... before damage occurred... but we are not told
So with a receiver (Barnard for eg) with a yield of ~165k, appropriate sized lugs etc and this new chambering and brass ( take your pick or make one up) whats the stop point and what process do we go about getting there?
Lets say brass is good for 88k psi as per the mfgs say so
If you get to 70k psi and everything is indicating sweet, then why not 75k?, 80k? if all good there also, after all, this aint your grandaddies deer huntin' rifle
Arnt we at the same stage back in time when 50k psi was PMAX and then with the advent of stronger actions/materials etc, we saw a new class of cartridges at 65k psi
Spanner are you suggesting that the lug shear point on the Barnard it at 165k pressure in a Chey tac case? Using your extensive reloading knowledge, what do you think is a reasonable pressure to run 375 cheytac brass in a Barnard action at? Do you think KG is over 80k pressure?
No - simply stating the yield of the receiver is ~165k psi as a mechanical property
I could do the shear calcs in about 10 mins with some dimensions - I have some drawings for the Barnard somewhere here, but I dont think it has bolt and lugs on it
I can find no mechanical reason as to why 80k would not be a pressure easily obtainable and run as long as you are within normal signs with the brass (as much as I hate using a pressure number as limit/reference) however the chambering may start to exhibit the signs at 75000 or less... or more... The point at which this happens is unknown to me right now.
With an action of suitable strength, why cant modern strong brasses like Lapua small primer 308 etc be run to the same signs you would say Winchester; if the action is not an issue and you're not exceeding the brasses limitations, then what reference does pressure actually have other than a final figure?
The point of the brass is to be able to run it harder - thats why they make it
Do I think KG is over 80k? 100% definitely NO
I could guess at a number, but it would be only that, however the brass shows no signs after 5 firings and having never been FL sized still chambers, there is no measurable expansion and the primers are snug as a bug. Maybe a couple of grains more powder will change things and it will hit a brick wall, maybe there is room for 5gr more and the cases just require a body bump?
Only more testing will say how much if any headroom is there, and if the final numbers say 72k or 82k, then so be it
Out of interest, whats the water cap of your chambering?
As you say the brass has been designed to take 88k. It may not show pressure signs till this pressure, you don't know as you haven't seen any. So you could be subjecting your action to this much pressure and you don't know. Now you have stated that you see no mechanical reason why the action won't stand up to this, however you have no numbers to support that and at this stage you are just guessing. The action may well take that pressure I'm not sure but I know if I was going to push the limits of something I would like to know at which point failure is likely to occur.
You seem to have no regard to reasonable safety factors, in fact you seem to ignore the point, running at just a few k psi below the failure point of the brass seems like a big risk with little reward. Safety factors exist because shit does go wrong, and when it does without saftey factor it can cost lives.
For me I will keep my ammo bellow 70k, I don't believe that the chey tac case shot out of a Barnard action is some new super round that is safe at 10k or more than other modern well designed magnums. The fact is that the 375 chey tac case and strong custom actions are a combination that has been used for several years now, for KG to be the first to discover that it is safe to push way above the accepted norms seems hard to believe.
Like I have said many times, if you are comfortable shooting you ammo at this pressure you are free to do so it doesn't effect me, I just don't think you should be telling people it is safe to do so when you certainly do not know all the facts.
As mentioned before, given the mfg receiver specs we're in a way different league to a 700, so why are limiting ourselves to those specs?
Hell when eveything was on Lee Enfield, and 1903 actions, noone would have ever dreamed of putting a WSM or RUM through it.
The advent of technology and evolution gives us the equipment, materials and processes that far surpass that of 40 yrs ago.
Do you have numerical data to say that 67000 psi is safe? what bolt thrust is generated and shears involved? - I doubt it
What happens when some idiot build a 375/408 on a 700 and uses the justification that its 338 pressures? - not even apples and oranges
I have a big regard for safety factors - you;re making presumptions that the pin is out of the grenade where all logical testing proves otherwise.
What if I told you it was at 70k (not saying it is or isnt) - would your opinion change?
How did magnum design come about when the norm was 50k psi, and why cant their be another step - there was from black powder to smokeless, and from 35k to 50k also, so WHY are we at a point where you CANT develop anything further?
I quote Mr Bertram 'why run your new V8 on kerosene?'
You seem to be hung up on the fact that where you are for whatever reasons is safe (which is totally fine) but anyone else is wrong.
You have no facts either - only what you are comfortable with based on opinion or superstition.
Why cant the natural progression of development continue - why all of a sudden has hundreds of years of cartridge development stopped in 1989 (338LM) - a long time before big custom actions and brass - which bear little resemblance to then.
I dont mean any of this to come across as a dig as I am genuinely interested in all things guns and this 375 topic and another wildcat have taken my interest.
Both are old and new ideas clashing.
I strongly believe we are at another step in performance and testing and physics will confirm or reject this
As I mentioned before, I'm in negotiations for a Universal receiver for pressure testing so more real data may become avail in the future.
If you could take a pic of the action lugs and bolt - square on for both, and side on for the bolt , I'll draw some points to measure on the pic
Send the info back and I'll do a shear analysis on it.
I have no doubt from rough calcs I've already done, that you will damn near vaporise brass before you have an action issue.
Remember - this aint grandaddys deer huntin' rifle :)
67k is not something that has been run in a case with a .640 case head for 30-40 years Spanner.
The 408 and 375 chey tac were designed to run at normal magnum pressures of around 63k.
I know that my action is safe at 67k because KG has done the proof pressure testing for me:D
No seriously Greg Duley has loaded it higher to check pressures and signs and found them, so is happy that we are safe at 67k.
I really just don't get why you guys think that you have stumbled on something that other experts in the field have not been able to do to any degree.
All you have done is push the brass and action further into the danger zone, this is not something new, idiots have been doing it for years.
im back.......................
Hey
What's up?
Nah mine are all good bro
I know because
wait
fuck
Little bit of a twist of what I implied there.
You originally said your 67 was based off the LM pressures......
Hey if you've gone higher, found the pressures and come back, then sweet as - not discounting that at all.
But broaden your outlook a bit and consider 'what-if' someone is doing something different that works....
What about Carlocks +P - go back 4-5 yrs or whatever - the 338 Edge has progressed has it not?
Once again you're 'presuming' the pins out of the grenade, maybe you're not shooting the same chamber, and maybe something else isnt been given away just yet.
This is all in regards to the 375, but as a broader picture the discussion of a development still has validity.
Are you wanting to go through with shear analysis?
You are guessing, without knowing my case capacity, seating depth, throat design, bullet coating..........
I was told by Daniel (CE Bullets) earlier this year when I was shooting the 400s out of my 375 Terminator that I had the second highest velocity that he knew of at that time.
That case was "over 67500 PSI" as well, but it is on the same action & barrel combination (7.8 exit twist) with Lapua brass that survived 15+ firings.
There is very little data out there with the large 375 CE pills simply because very few people have shot them.
This is mainly due to barrel twist rates & people willing to think outside the square, as I did when I asked Daniel to make the 425s for me.
I'm not particularly happy with being singled out & accused of over loading a case when mine is different to others.
Not to mention there is basically no other load data available for the 375, 400, 425 pills shot out of an imp Cheytac case like mine.
Here is something to think about.
My CE 350s run at 3350 FPS out of a 32 gain twist barrel with Retumbo with what I judge to be similar pressure to the 400 & 425 pills.
Kirbys 375 Allen magnum data on his site with a 30" barrel & 350 SMKs states 3300fps with Retumbo.
So if you are going to continue to accuse me of over loading to the extent that you are, I suggest you talk to Kirby as well........
There is a very good chance that the DCM has a greater capacity than the 375 AM.
You can choose to run your loads at what ever pressure you are comfortable with, as can I.
Nobody here is thinking far enough outside the square - brass is gay, want more speed throw away the brass, buy a yellow bastard and toss a 250gn pill at 3850fps. If you build a complete system around max velocity and specify an action to take the bolt thrust you are sorted.
Shoving big cases into rem's etc all seems a bit like boy racers putting kits on nana's old mitzi to me - its never going to be a race car, if you want a race car go build an effin race car...
As for the universal reciever I suspect that building one would be easier than importing one (and paying for it)
Big block of steel, bore hole through and thread both ends - front one gets the barrel with extra long tenon (with savage style barrel nut for headspace) back end gets a breech plug (2 inch HT bolt with fine thread should hold a few kpsi). Firing pin drilled through the bolt centre only needs to float free and project just past the end of the plug in either direction, simple spring loaded striker to fire the round - hint dont stand behind it if a primer pops, could possibly put in a safety feature like a curving up bracket behind to send it skywards. If you want to explore MAAAAX pressures chamber the barrels deep so cases fit flush like a pistol, headspace by winding the barrel down onto the plug. Sorted
@Toby did you try this yet?
This thread made interesting reading.
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