Thread: Wilcats and Pressure

Originally Posted by DAF

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.

Yip - the yield point/yield strength
Stress is proportional to strain and is a straight line with the gradient of the modulus of elasticity (IIRC), until it reaches yield strength in which permanent deformation occurs.

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

Originally Posted by The Claw

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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3 of the 4 rifles use Tikka 595 actions & the other is a vixen. All done by the same gunsmith, and a very good one at that...

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Originally Posted by The Claw

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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FL sizing was just an example of yield of the brass
If the primer pockets are opening up, then obviously its past point of yield
Not sure how it fits in to be honest LOL

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.

Originally Posted by L.R

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.

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

Originally Posted by L.R

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.

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.

Originally Posted by L.R

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.

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?'

Originally Posted by L.R

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.

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

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.......................