Thread: Wilcats and Pressure

http://www.longrangehunting.com/foru...re-safe-40117/

This post by Kirby Allen is what I was after. Very interesting reading and relevant to spanners post regarding brass failing first.

Originally Posted by Tui4Me

Rem 700 action how much chamber pressure is safe? - LongRangeHunting Online Magazine

This post by Kirby Allen is what I was after. Very interesting reading and relevant to spanners post regarding brass failing first.

Thats good enough reason for me to want to question the pressure being run to achieve XXXX velocity... And I know that every barrel will be slightly different etc, but surely not to the point that the differences reported in other threads would be explainable.

Notice in the 1st article I posted there are some very interesting points regarding ackley case shoulder angle, suggesting almost straight taperd angled cases reduced bolt back thrust, had better extraction and increased velocity...

For something not meant to start a shit fight you have used a very emotive writing style...

Interesting articles there. I think it goes a long way towards saying the effects of.and measuring of pressure and the things that influence it is still relatively unknown. It also highlights that some of.our generally accepted pressure indicators may not reflect the goings on as well as we believe

Big wild cats certainly are a whole different ball game all together.

I'll stick with my common 7mm RM I think

Thinking back to my old life as an engineer I seem to remember that a cylindrical pressure vessel exhibits twice the force on the ends as it does on the sides. So that makes the bolt lugs the most worked surface in the action (weakest link in the chain so to say).

Now pressure is force divided by area or

P = F/A

Therefore force equals

F = PxA

So the bigger the area (the internal diameter of the case) the bigger the force. So a small cartridge loaded to 65000psi will exhibit much less force on the lugs than a magnum case loaded at 65000psi.

Now every material has both tensile and compressive properties, and once those are exceeded it’s considered a fail. Most engineers build in a FOS (factory of safety) to give some room for error, so if you choose to load above a certain point you are eating into this FOS.

Basically you can't beat the maths on these things...load it too high and it will fail eventually through fatigue.

kj

I think I may have worked out Mr A's secret... He has flames painted on his rifle... (see 260 loads thread)
This also supports my conclusion that he is most likely an idiot with little regard for his own/others safety for loading at excessive pressures to achieve xxxx velocity. Each to their own though, and possibly I'll be proven wrong, but in the meantime I'm happy to forego a little performance to save my life possibly...

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Originally Posted by The Claw

I think I may have worked out Mr A's secret... He has flames painted on his rifle... (see 260 loads thread)
This also supports my conclusion that he is most likely an idiot with little regard for his own/others safety for loading at excessive pressures to achieve xxxx velocity. Each to their own though, and possibly I'll be proven wrong, but in the meantime I'm happy to forego a little performance to save my life possibly...

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OMG that flame job is horrible!! Why why why???

And THAT is exactly what this thread is about
What is excessive pressure in something that does not have any pressure guidelines - sometihng completely new

You cant run to a SAAMI number as there isnt one, you can only run to signs of pressure, but if soaking your projectiles in goat piss gets rid of all the pressure signs you just had at XXX point and you can now get 10% speed more out of it before getting to that spot, then are you past the limit?
And what is this 'limit'? one that you have given yourself at some time because there isnt an industry standard? - then what if the guy next door uses tahr piss? and gets 12%?

What about the idea for eg of a super Weatherby throat (no idea on this its just an example of what-if)
Let say your 308 can run 2900fps - crazy idea - give it SHITLOADS of freebore - 4x that of a Weatherby - get a reamer made, shove it up its bum and voila, you can now get 3050 out of it before pressure signs - unsafe? well the action will hold Magnum pressures and you;re not there, and the brass isnt getting wrecked, but your mate who can only get 2950 before wrecking brass etc is going to slap you up the side of the head as you;re faster than he can get and using 3 more grains of powder.

30-06 in a 1903 was about it 110 years ago, 300 RUM is going to blow up a gun of that construction, but in a suitable action we have something that far surpasses the ol -06
Having an open mind and thinking outside of the square/triangle/circle is whats given us all these calibers over the last 100 odd years.

Yes, there are most likely tricks and secrets out there on how to get more velocity for a given pressure, but then there is also a point where these tricks have been used and only more pressure will give more velocity. If you have pressure testing gear, why not just publish what pressure you are running at then punters can make up their own mind about whether they think its safe. I for one, wouldn't touch a wildcat chambering, or take any notice of quoted velocities, without having an idea of the pressure required to achieve said results. Especially when its got well in excess of 100 gr of powder about 15cm from my face...

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Because the numbers from pressure testing gear seem to be as good as made up??

Originally Posted by The Claw

Yes, there are most likely tricks and secrets out there on how to get more velocity for a given pressure, but then there is also a point where these tricks have been used and only more pressure will give more velocity. If you have pressure testing gear, why not just publish what pressure you are running at then punters can make up their own mind about whether they think its safe. I for one, wouldn't touch a wildcat chambering, or take any notice of quoted velocities, without having an idea of the pressure required to achieve said results. Especially when its got well in excess of 100 gr of powder about 15cm from my face...

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Once again the whole point to this thread.
This new design receiver with new design case is at 87654psi
You cant even go and buy the same pressure gear and see if its true or close or anything as its no longer even being made.
You then 'make up your own mind as to whether its safe' - based on what information? Jimmy saying it right, or Bob saying its not?
The slow one is exhibiting all the pressure signs and thus at a brick wall, where the fast one has none of them
You have a number which is 100% meaningless as there is nothing to refer it to as its all new- its a number and nothing more, but if 87654 is a number you play in the lotto and makes you feel good, then by all means use that to 'make up your own mind as to whether its safe'

One of the wildcats in my interest is low pressure ~40,000psi and pressure doesnt even start to come into it and is not quoted.
One guy can get it SMOKING along and has more data than anyone else from testing, another whos playing with it is breaking bolt lugs off after 50 rds (AR15) and cant get close with the same load data. Speedy has (lets say) 1 deg more case taper and a 20 thou longer throat- thus less initial bolt thurst and less initial pressure before the case grabs the chamber walls - something he isnt telling Slowpoke
If slow poke says he wrecks things at 40k and has to pull it back to 38k to get it to last, and Speedy says hes running 41k with no issues ,which one would you buy? The one thats at its limits and past it or the one with the performance, that surpasses it?

OK, I'll have to admit that you have lost me with the first part there, but if 87654 is the lotto numbers I'm going to use my winnings to build a 5lb 375 super magnum that pushes 425gr projectiles @ 4,000 fps and has an infinite barrel life, that way I'll have something clearly superior to anything based on current information...:thumbup:

I know nothing about AR's, but if 40k psi is within the FOS (to use kj's example above) and there is plenty of reliable data on the performance version you would have to go with it wouldn't you?

My main interest/concern is that whatever load is being touted as being superior, but within safe parameters for the given action and brass combination, is just that. If Zeek has created some new super action, surely a statement something like "has been tested to xxxx pressure for xxxx rounds without failure" and the loads developed are xxxx - 10k psi (or whatever margin is deemed prudent) would show that in fact the velocities aren't just achieved by overloading?

If there is such an action out there, surely people aren't going to just blindly buy it/build on it without some sort of hard data?

Or have I missed the point again?

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Spanners you really are talking shit. My 375 Lunatic is at 67,000psi and makes a 400gr projectile go 3035fps. Kiwi Greg's 375 DCM is at ???? Pressure and makes a 425gr projectile go 3080fps.

Kiwi Greg's is at a higher pressure and therefore makes more velocity. End of story.

If its safe of not will depend on what Barnard have designed the action to take. Why don't you call them and ask if they are happy with the pressure Kiwi Greg is putting on his action insted of speculating all this shit.

Originally Posted by The Claw

...... fact the velocities aren't just achieved by overloading?

But where is the point or max to quantify a statement of 'overloading'
Maybe the fast one is 'normal' and the slow one is 'underloaded'?

With no SAAMI data, is the person that has shot 10 rds setting the standard or the person thats shot 500rds in a better position to set it?

OK I have seen this discussion going on for a while and not being an expert I would like to make a couple of observations and ask a couple of questions.

With any cartridge, whether a known quantity or not, starting loads can be reasonably easily established from already available loading data, or sensible comparision with other cartridges of similar capacity/projectile selection.... yes?

Sound reloading practice from suitable starting loads generally shows incremental increases in pressure evidenced by case head expansion, velocity spikes, increased bolt lift, excessively flattened primers yada yada...

The main issue we face as reloaders is: - to not have excessive pressure affecting our brass, as brass failure is our primary concern?

Brass is almost always the weakest part of our system. Brass failure is something that we need to ensure that we completely avoid.

The setting back of lugs, resulting in headspace increase over time is a possibility with repeated use of hot loads and is more likely to occur with strong brass that may not show
excessive pressure signs as readily?

However if that is occuring, we should see an increase in the signs of pressure on the brass as the headspace increases. As indicated in Kirby Allens post referenced earlier..

So we are now back to the start.... I would assume that it is unlikely that catastrophic failure is going to occur with a single hot load with new brass, a correctly headspaced low use rifle if the hot load is not a complete cockup.

Every other situation we should have progressive brass pressure signs before catastrophic failure...

Repeated firings that do not result in the need to resize, would be unlikely to be setting the lugs back in a rifle..?

Is a strain gauge giving a pressure reading a reliable predictor for brass failure? I am getting the impression that it is not (relative action strength, brass strength etc)

Is a strain gauge a predictor for the potential of action degradation as a result of hot loads over time? Potentially I think it may be .. yes? Are the other indicators of pressure in terms of brass and increasing headspace sufficient without a strain gauge? .......most probably - but you are in effect waiting for the result rather than predicting it.... and that may be a useful result.....

Is a strain gauge a valid comparator across differing rifle setups? Probably not from a scientific perspective, but in broader terms, experience would give some statistical probability..?

Is a strain gauge a useful tool for the comparative establishment of sensible pressure boundaries in a single rifle, (along with other indicators) or as illustrated by KG with choices for optimal powder selections? I would think obviously the answer would be yes..

I see it as another tool, that can assist particularly in the development of new cartridges along with other existing indicators.

It is possible however to use the basics well in that process without the need for a strain gauge.. The danger in my view is reliance on data from another rifle producing x pressure with a certain load, and using that load in your own rifle without doing proper load workups.

Asking a question about pressures (from a strain gauge) because of a concern about what is seemingly a strong loading; is valid? A response should be qualified in terms of case life, pressure signs resizing requirments, action specifications etc... but that information is hardly a commercial secret?

Help me if I am not getting it....but I think that this discussion while helpful has been being argued from differing perspectives, and neither position is completely wrong or completely right?

Yes/no?