Thread: Wilcats and Pressure

Because we are using actions and brass similar to say 338 lapua which has a safe working pressure of around 65-67k. What makes you think that it's sweet to run cheytac brass up to 88k when nothing else has a safe working pressure that high? Have you confirmed with Barnard that they believe their action is fine to take that much bolt thrust?

So a number was come about and worked to - and based on the number that was come up with, everyone else is 'overloaded'?
A number worked too with equipment that has a number of weak points.
'What if' the gear is reading 5% high - you now are ~3000psi shy of your self imposed number

The 338 LM was CIP accepted with a 250gr proj as a standard for use in 700 sized actions by the military 23 odd years ago
The fact that nothing SAAMI or CIP approved above that pressure is a pretty narrow minded approach to development.
Mentality like that from someone like Ackley would have us in a pretty vanilla work as far as calibers go nowadays

Brass and actions barely resemble what was originally on offer in circa 1989, surely we're well and truly in a 'bigger and better' world?

Where does this 88k psi come from?, its a number widely thrown around

I doubt very much if Steve would give you a number, however without bolt lug setback and/or stretch, you'd be pretty safe from a mechanics and physics point of view to say you are well within the strengths of XX action, afterall, without setback you havnt hit the yield of the material, which will more than likely be in the range of double the pressures we're talking
Steves a smart cookie, maybe a little eccentric, but no slouch.
I'm sure he has done the lug shear calculations, I wouldnt mind doing them myself. Some calcs I've seen have a FOS of 2 in them.

In regards to bolt thrust, I presume you have cut 375 Bertram brass and seen the base of it? given what you will find in there, you will actually find that the bolt thrust will be LESS that that of using Cheytec or Gibbs brass (not that anyone uses Gibbs, but its an example of same sized case with same pressure having a big difference) due to its internal base diameter.
Thrust is easy to calculate - you only need PMAX and area the force is acting on - in this case internal area of the case head.
I think it would be moreso reduced due to its design which is probably more of an artefact from manufacturing

This thread is pointless!!!!!!

Originally Posted by baldbob

This thread is pointless!!!!!!

Thanks for your valued input.
You can admit its over your head, we wont think any less of you

Originally Posted by Spanners

Correct - however the DCM is not the same chambering is it not?

Any reply to the 67k questions?

Now I'm confused? The first line of KG's 375 DCM thread says that it is a 375/408CT Improved? Sure it will have subtle differences but there should be some similarity with the results seen?

87654 or 88k if you like came straight from you in a earlier post.
You make a lot of assumptions about how strong an action is and how much pressure they can take. If you read the link posted a few pages back you will see that Kirby Allen has had lug set back in an action way before double the pressures we are talking about as you suggest. Sure a Barnard will be stronger than a Rem action but it needs to be to cope with the much higher bolt thrust generated by the Chey tac case.

You seem to suggest that as long as you are not seeing any lug setback you are safe, you may only be 500psi off this point and you would have no idea. This does not give much margin for small things to go wrong.

You have come here suggesting that KG's load is safe because no one can prove to you that it's not. Why don't you do some research and testing and prove that it is safe, a good start would be to publish the pressure figure of the load he is using. I believe that hiding it is what is leading people to suggest he is overloading.

Personally I am happy with mine at 67k and I have no problem with KG and his customers loading to whatever they think is appropriate.
I think in time the reasons to keep the load at more normal pressures could become apprent.

Originally Posted by The Claw

Now I'm confused? The first line of KG's 375 DCM thread says that it is a 375/408CT Improved? Sure it will have subtle differences but there should be some similarity with the results seen?

Hmmm.. not sure how to reply - obviously there are some details that are different which cant be divulged by me as its not my case design or place to do so

But are we not in a position now that 67k psi is a number selected by the shooter/builder of one chamber based on the 338LM rather than an actual pressure that is deemed safe in this configuration through, brass, action etc signs?
I consider them different chambering to be honest as there is a difference maybe albeit subtle and a couple of other things that contribute

Which brings us back to the original topic of creating wildcats and where/how you draw the line

Originally Posted by Spanners

Thanks for your valued input.
You can admit its over your head, we wont think any less of you

Not over my head wee spanny!!!! Just seems pointless I dont see what your trying to acheive here.... As you were

Again Spanner you are assuming that you know how the cases are different. You have never had a Lunatic case to measure.

Originally Posted by baldbob

Not over my head wee spanny!!!! Just seems pointless I dont see what your trying to acheive here.... As you were

Ok - I'll make it simpler.

I get a brass mfg to make me some brass I designed in .345 Superwisbanger caliber. (or .123 Humdinger)
Get the biggest gruntiest action I can get and work some loads up as per you would with any other caliber, ladder, chrony data, measures cases, primers, action signs etc etc
When do you stop, and why - your pressure gear says 200,000psi (stupid number I know), but everything else is just sweet - no signs whatsoever of any issue.
Cases lasting multiple firings, no expansion, dont even need to FL size, everything is MINT
You fire a few more hundred rounds and still O for awesome.
Is there still room to go further or not? if not then why? and if yes, now where to you stop?

You stop when you reach a comfortable pressure for the powder/brass/action/pill your using.....

Doesnt matter if your loading .223 or .375 lunitic its basic reloading practise ABCs kinda thing...

Therefore I think its pointless...

Originally Posted by baldbob

You stop when you reach a comfortable pressure for the powder/brass/action/pill your using.....

Doesnt matter if your loading .223 or .375 lunitic its basic reloading practise ABCs kinda thing...

Therefore I think its pointless...

I think you just confirmed the point he was trying too make Bob.

Originally Posted by baldbob

You stop when you reach a comfortable pressure for the powder/brass/action/pill your using.....

Doesnt matter if your loading .223 or .375 lunitic its basic reloading practise ABCs kinda thing...

Therefore I think its pointless...

BINGO!
If all the ABCs are correct and the pressure gear says 200k psi then for this caliber and combo etc is 200k too high?
And if yes how and why?

As much as you think this maybe pointless, I think its a good discussion

+1

R93

Originally Posted by L.R

87654 or 88k if you like came straight from you in a earlier post.
You make a lot of assumptions about how strong an action is and how much pressure they can take. If you read the link posted a few pages back you will see that Kirby Allen has had lug set back in an action way before double the pressures we are talking about as you suggest. Sure a Barnard will be stronger than a Rem action but it needs to be to cope with the much higher bolt thrust generated by the Chey tac case.

You seem to suggest that as long as you are not seeing any lug setback you are safe, you may only be 500psi off this point and you would have no idea. This does not give much margin for small things to go wrong.

You have come here suggesting that KG's load is safe because no one can prove to you that it's not. Why don't you do some research and testing and prove that it is safe, a good start would be to publish the pressure figure of the load he is using. I believe that hiding it is what is leading people to suggest he is overloading.

Personally I am happy with mine at 67k and I have no problem with KG and his customers loading to whatever they think is appropriate.
I think in time the reasons to keep the load at more normal pressures could become apprent.

Sorry - should have been clearer.. 87654psi was a number I pulled out of my arse, but 88k is a number I have seen mentioned a few times as to the strength of the brass - was just wondering where that number came from thats all, though from your reference to 88k and not 87654 that you were using it as a figure.

I did a fair bit of dicking around with cases and the gun etc,
As far as pressure goes, I completely avoided the topic via strain gauge as I give it little merit regardless of brand in regards to a number. I ran racecars on dynos for years, and know the differences between machines - and its the same situation.
We're not dealing with something thats been shot for 50 yrs in the same construction of brass and receiver and thus pressure really has no influence IMO
If this case was designed before any 'magnums' were CIP or SAAMI approved, would you load to 50k psi and call it quits? of course not - thats where and how magnums were developed. Are we not talking about a magnum magnum now? if so then why are we limiting things through a set number from 30 years ago rather than working with the case to see where it goes?

If you can load the same case 5 times without FL sizing, primer pockets are tight as a tiger and there are none of the ABC signs from common sense reloading, then pressure of XXXpsi means what?
Back to a point I made earlier - overloading is loading more than a standard - the standard appears to have been set by pulling a number from thin air or from a completely different caliber 1/4 of a century old