i said

quote:

Originally posted by jeffeosso:
- as pressure does not equal velocity -- (ever) .. WORK equals velocity.

and physicists state the same..
http://en.wikipedia.org/wiki/Work_(physics)


then alf attempts confirms it, except his equation is over simplified

quote:

Originally posted by ALF:
dW = p*dV

quote:

Originally posted by Warrior:

quote:

revokes all the "thought" that pressure means velocity

Jeffe,

You sure don't mean that pressure and velocity are totally unrelated?

i said

quote:

Originally posted by jeffeosso:
- as pressure does not equal velocity -- (ever) .. WORK equals velocity.

quote:

Originally posted by Warrior:

Nobody it is saying it is a pure linear relationship, where y = mx + c.

correct.. and here is where i leave you to expound

quote:

Originally posted by Warrior:


However, between minimum and maximum published loads,

you can do lots of things, and not one of them shows that more pressure directly means a proportional increase in velocity.

thanks fellas, have fun

Jeffe is 100% correct.

He did not say that Pressure is not related to Velocity. Unlike alf and warrior who are simply transcribing information from books, Jeffe's point is Velocity is created by the amount of "Work" being done within the Pressure Envelope. The Bullet has moved Forward at a different Rate, which alters the Chamber Volume, Reduces the Pressure, and slightly changes the Burn Rate.

Reality once again bashes alf's and warrior's great Transcribing capabilities, and total lack of first-hand experience. Even the rawest Rookie will see it on either a Chronograph or especially on PRE when certain combinations of Cartridge components go together.

Wow!!!

Warrior

quote:

Originally posted by Warrior:
Wow!!!

Warrior

WOW X 2!!! A bridge too far. roger

Roger,
lets make it easier
take a 250 savage and a 257 weatherby --
in fact, we'll assume we use the SAME, rechambered barrel

lets say we have some "certified" loads, of oh, 65K psi.. and the same box of 100gr .257 bullets - these are loaded with case appropriate powders (not 65k of bluedot!!!)

and a 25" barrel

fire 5 rounds of the 65k psi 250 savage over a chrono and record the vels

rechamber to 257 weatherby, and fire 5, 65k loads over the same chrono

***IF*** preasure meant velocity (using alf's equation, if you like)

please explain the 500 FPS difference in the 257 weatherby?

one can't explain that with pressure alone...

so, its more of a VOLUME/TIME/PRESSURE function, rather than a (over simplistic) pressure problem...

aka WORK...

or, another concept ...
2800psi will drive a 150gr .358 bullet about 900fps ... in the crossman rogue airgun

while the 38 special needs roughly 15,000PSI to do with same?

therefore pressure is NOT the primary cause of velocity...
extreme (and dumb)example
if it where, one could bould a 24" diameter .257 (yes, diameter), 24" long barrel and load it to "infinite" pressure, and exceed 9000FPS, using pistol powder (really fast)

except you can't -- that's faster than the expansion of the gas..

another example .. "fast" and "slow" powder.. why do we use "Fast" and "slow" powders, at the same PEAK psi?

to utilize the TIME portion of the equation .. to go faster, in the same case, with the same peak PSI...

this is actually REALLY basic, and EVERY, i repeat EVERY reloading manual has this presented, in black and white.. its merely non-obvious

"how's that?"
every reloading manual clearly shows load data, right?

say the same 257 weatherby has 10 powders listed for the bullet ...

these are allow loaded to very close to the same powder (some books even explain hwo they get there) which is basically max-safety and everything is loaded to that book max.

does every powder listed produce the SAME velocity?

why, other than hornady (listing target vel with safe powder) NO .. there's 50, 100, even 150fps difference, aren't there?

again, its as plain as black and white.. its just non-obvious

quote:

Originally posted by ALF:
You bloody fool ! Who the hell do you think you are ?

cute.. let's keep this post for when he sobers up and starts deleting his posts, AGAIN ...

alf - aka "HUNDREDS of posts that solely contain the symbol '.' in them" .. as he likes to go clean up his ramblings when he's proven wrong

Let's make this real simple: burn rate for any powder in any cartridge only becomes reasonably consistant within a moderately narrow pressure range and that demands near max charges.

A 30-06 with a 150 gr bullet and a moderately slow powder like IMR 4350 approches that prime pressure range at about 55-57+ gr. Below that level the burn rate will be too variable to make any solid appraisels of what's going on.

Anyone wishing to load lower velocity .30-06 ammo should use a faster burning, easy igniting powder such as 4895, not a reduced charge of a slower powder.

The VC Factor and its use:

A very useful measurement for the reloader is the V/C factor. Whilst very basic in its mathematical format, it cuts through all the complexities and measures the ultimate result, just short of knowing the actual operating pressure. It does not just address the propellants behaviour, but also all the internal dimensions of the rifle and its interaction with the bullet and its bore size. It can be found by dividing the muzzle velocity (measured with a chronograph) by the propellant charge, to yield a velocity per grain of propellant used for a specific type of bullet and its weight. V/C comparisons between different cartridges have no practical value, other than to state that one is ballistically more efficient than the other one, even if they are of the same calibre and the same bullet weight is being used throughout – be it a 308 Win; a 30-06 Spr or a 300 H&H. Also remember that two different propellants will yield different V/C ratios in the same calibre – so the V/C is inextricably linked to the type of propellant in a specific cartridge.

A car’s speedometer tells us how fast it runs, whilst the revolution counter tells us how hard the car is working. We could also apply this line of thought to a rifle. The V/C tells us how hard the rifle is working. When one goes up, say half a grain in a near maximum load, and the V/C drops, it is a tell-tale sign that we have exceeded the ‘ballistic optimum point’ of that specific bullet/load combination, as we have now reached a point of diminishing returns, indicating an over maximum load situation. From this point onwards, the velocity/pressure relationship is not linear as pressures escalate without velocity increases. The reloader should compare his rifle’s velocity and V/C factor with Somchem's maximum velocity, as it is tantamount to maximum safe pressure in a given cartridge with a specific propellant as determined by the lab facility. (Bullet type and AOL should be similar). The caution is, that if you obtain a higher V/C in your rifle than in Somchem's booklet, which is based on minimum CIP specs, then you must not load to their maximum load in grains, otherwise you will exceed the maximum velocity and hence the maximum safe pressure.

It is quite common for some rifles to yield 6% higher velocity by virtue of tighter internal tolerances – 140 to 180 fps more. The opposite is also true, if you are running lower V/C’s, your velocities and pressures are lower. Without velocity measurement, you will never know how you stack up against published loads. Over time the throat of the barrel will wear out and you will have to increase your load to maintain the same pressure and velocity. Again, if you never bother to measure the velocity, you will never spot this occurrence.

As Somchem does not publish pressure figures, we will not exactly know how far they are off the CIP maximum pressure, if at all. Nevertheless, it is a sensible approach that I have suggested not to go by maximum propellant weight, but rather by maximum velocity, contrary to other reloading sources, as there is a direct relationship between pressure and velocity. Somchem, unlike the Lyman Reloading Handbook, does not publish pressure figures, because they believe too many factors influence pressure and reloaders may just want to go for a hotter load when they see a relatively low published maximum pressure. This in turn fuels the speculation that Somchem have indeed opted for a safety margin over and above the CIP max. The problem with this approach, assuming that Somchem has taken an additional 5% safety margin, is that some cartridges might be closer or right on CIP max than others. Some cartridges are more forgiving than others and some cartridges just battle to give desired velocities with Somchem’s propellant so they are loaded a bit hotter. Most reloaders assume that when the telltale signs of pressure are absent (flat primers and stiff bolts), then the pressure is not above recommended levels – this is simply not true, as some cartridges are just more forgiving than others and each rifle system is different.

Reloaders without a chronograph are missing out on a very important tool, as velocity measurement is an excellent indicator of the nett result of all internal ballistic imponderables. Velocity measurement clearly shows your level of load uniformity by focusing on your extreme spreads that you obtained. When you change a component (primer, case, bullet or propellant) or vary the seating depth, the measured velocity tells you how the new load combination behaved ballistically. More often than not, monolithic bullets will produce higher V/C values than conventional bullets, but that is at the cost of higher pressures. For that reason, lower start loads are recommended in reloading manuals. In the absence of pressure testing, velocity measurement is our next best guide.

Internal ballistics is a very inexact science, but we do have certain principles that can guide us. The danger is our ignorance or that we underestimate the dynamic behaviour of internal ballistics, as we generally see things in the ‘slow’ world and not in the ‘dynamic’ world. The main problem seems to be the variable behaviour of the propellant whereas mechanical rules stay the same. If one propellant worked equally well in all cartridges, then it would have been only a matter of deciding on the quantity of the load. If pressure did not affect the burning rate of the propellant and it was insensitive to temperature changes, we would have had a far more stable and predictable situation, but that is not to be.

Warrior

Chris,
when you lift directly from someone else's IP, its always nice to CITE the work as not your own

Excellent example Jeffe. I'll guess there will only be two people in the thread that don't understand. - The "Transcription Kings".

quote:

Originally posted by jeffeosso:
Chris,
when you lift directly from someone else's IP, its always nice to CITE the work as not your own

Hi Jeffe,

You assumption is wrong - the above is part of an article I wrote in 2004 for SA Hunters - my own work, buddy.

Regards
Warrior

Hot Core,

You obviously understand everything without having to read or study anything - not from books nor from your peers or those before you, like you aquired all your knowledge prior to birth.

Attacking people like you always do does nothing for your reputation. It would be far better to share and teach and take people with you rather than to belittle and demean them in a condescending way.

Warrior

so, chris, i am sorry for assuming you to be lifting. i dont agree with your opinion piece, however

now, as for my 250 v 257w strawman.. please explain how identical pressure, bullt, and barrel result in drastic diff in vel?

quote:

we aren't burning nitrocellulose, my friend.. americans haven't for a long time. i know what you meant, but what you SAID was wrong

http://en.wikipedia.org/wiki/Smokeless_powder

Maybe you thought I said Cordite?

quote:

pressure and velocity are NOT directly related .. doesnt matter how much you stuff your fingers in your ears and try to ignore it.

Me? I am deafer than a stump of wood and all, but what brought this down on my head?

quote:

Originally posted by jeffeosso:
Roger,
lets make it easier
take a 250 savage and a 257 weatherby --
in fact, we'll assume we use the SAME, rechambered barrel

lets say we have some "certified" loads, of oh, 65K psi.. and the same box of 100gr .257 bullets - these are loaded with case appropriate powders (not 65k of bluedot!!!)

and a 25" barrel

fire 5 rounds of the 65k psi 250 savage over a chrono and record the vels

rechamber to 257 weatherby, and fire 5, 65k loads over the same chrono

***IF*** preasure meant velocity (using alf's equation, if you like)

please explain the 500 FPS difference in the 257 weatherby?

one can't explain that with pressure alone...

Totally agree and understand what you say here. Originally I guess I misunderstood what you posted. Thought you were professing just the opposite. Perhaps a colloquial difference. roger

Slam fire
I apologize. My remarks were out of proportion. Thank you for calling me on it.

quote:

Originally posted by ALF:
It is a physical principle , PHYSICS 101 !

It certainly does not claim that:

Pressure = Velocity, never claimed it !

thanks for coming around alf.. good to see you understand the basics...

or, as it will say in a day or two

quote:

Originally posted by ALF:
.

Jeffe,

I do not have experience with the 2 cartridges you listed as having the same Max pressure, and I am therefore reluctant to make statements about their capabilities (presure and resultant velocities)

I just hads a look at Wikipedia and thre seem to differences:

1) Savage:

The .250 Savage was the first American cartridge capable of achieving its 3000 ft/s (914.4 m/s) velocity, and was created for use in the popular Savage Model 99 lever-action rifle. Achieving that velocity may have been the reason for the choice of the light-for-caliber 87 grain (5.64 g) bullet.[3] The cartridge has a pressure limit of 45,000 CUP set by SAAMI.

2) .257 Weatherby Magnum:

The .257 Weatherby Magnum is .25 Caliber (6.35 mm) belted bottlenecked cartridge. It is one of the original standard length magnums developed by shortening the .375 H&H Magnum case to a length of around 2.5 in (64 mm). The .257 Weatherby Magnum is among one of the flattest shooting commercial cartridges. It is capable of firing a 115 gr (7.5 g) Nosler Ballistic Tip bullet at 3,400. ft/s.

The .257 Weatherby Magnum has a case capacity of 84 gr. of water (5.45 cm3). Sources such as Lyman and Weatherby's pressure rating suggest maximum average pressure limit of 66,000 psi (4,600 bar). CIP limits the .257 Weatherby Magnum to a maximum average pressure of 4,400 bar (64,000 psi).

Look at the velocities quoted in Wikipedia for the same bullet weight:

Savage .... 100 gr SP bullet .... 2,864 fps in 24: barrel

Wby ....... 100 gr SP bullet .... 3,602 fps in 26" barrel

If we knock of 2" of barrel on the Wby, then there is still a huge gap.
I do know the pressure ceiling of the 250 Savage in PSI, nor if its case volume is the same as the Wby.
Wikipedia lists the pressure limit of Savage at 45,000 CUP set by SAAMI and may not be exactly equal to the Wby.

Based on the above differential in pressures, I cannot see that 45,000 CUP equates to 66,000 Psi (SAAMI).

Could you therefore confirm your source that the 2 cartridges have the same P-max.

Warrior



Warrior

I failed school algebra but was an ace in geometry. I am a trained sociologist and am also a competent business analyst......so let me try & understand this.....

Pressure is not just a "bang" but a "bang" our a period of time. So we get a pressure curve. A high peak and a quick drop in pressure (sharp curve) with a fast burning powder will give lower velocity. A lower peak for a longer time and a shallow curve can actually give higher velocity. Longer barrels give higher velocity - the bullet is under pressure for a longer time.

Another illustration - when Obama won the election in 2008, the pressure in the right wing community was very high and went up very fast. When the health care reform was passed the high pressure was sustained. When Donald Trump made all the noise, the right wing community had low pressure but when the birth certificate was released, the pressure shot up and really sky rocketed when Bin laden was killed. But Trump's campaign velocity came down very sharply. When Obama is re-elected, the right wing pressure curve will be back up again.....way up.

By the way, more heat = more pressure. Hence the tropical cordite loads in India and Africa. But velocity could be lower....like the heat on Trump leading to high pressure & low velocity.

Chris,
frankly, you provided lots of words, but avoided the question.. i provided you the circumstance and even stipulated that they would be certified to be loaded to the same pressure.

now, stop dancing around the question.

why does a 65k 250 savage load go slower, with the same bullet and barrel, with proper profile powders, than a 257 weatherby, AT THE SAME PRESSURE.

i realize you have a body of work that stipulates a thing about pressure. please accept that it may be incomplete.. then you can write MORE pages for dollars

quote:

Originally posted by Warrior:
...the above is part of an article I wrote in 2004 for SA Hunters - my own work, ...

This is not an easy issue to understand completely. The above information by Jeff is spot on. In short the increase in pressure by one grain of a given propellant is not linear as the pressure curve increases. This pressure curve of a specific propellant and a given bullet (not a bullet weight because bearing surfaces differ between bullets of the same weight) is dependent on many things but the key ones to remember are heat and volume. Read what has been posted above and learn something.

I'm voting for the screwy chrony! roger

Alf,

All this evidence that you present here does not fit the current majority thinking on this thread, as it is too simplistic and you are just confusing us here with the facts. We need something more complex like a riddle that we cannot solve, so that we can put it down as a mystery.

Positive correlations do not count !!!
Your quotations seem to be very one-sided and thus not balanced.

Warrior

the data CLEARLY shows non-linear RANGE of results, FITTED to a straight line.

Now, Chris, stop playing games, and answer my question.. why does a 257 weatherby go FASTER at the SAME pressure than a 250 savage (don't play CIP games, sir, if you are fit to answer the question, then you can accept the parameters)

quote:

Originally posted by jeffeosso:
Now, Chris, stop playing games, and answer my question.. why does a 257 weatherby go FASTER at the SAME pressure than a 250 savage (don't play CIP games, sir, if you are fit to answer the question, then you can accept the parameters)

Jeffe
Think of it this way: The 250 savage is going to hit peak pressure while the bullet is closer to the chamber than the 257 Weatherby. So the 250 will not be going as fast as the 257 when the pressure begin to drop from the peak. Now, couple that with the fact that the 257 will have more pressure for the rest of its travel down the remaining length of the barrel, it is easy to see that why the 257 is faster.

To put it into simple terms: the "pressure" that we should be looking at is not peak pressure, but the average pressure.

The 257 at a peak pressure of 65k, will have a higher average pressure than a 250 at the same peak pressure.

But maybe that was your point.....

quote:

Jeffe
Think of it this way: The 250 savage is going to hit peak pressure while the bullet is closer to the chamber than the 257 Weatherby. So the 250 will not be going as fast as the 257 when the pressure begin to drop from the peak. Now, couple that with the fact that the 257 will have more pressure for the rest of its travel down the remaining length of the barrel, it is easy to see that why the 257 is faster.

To put it into simple terms: the "pressure" that we should be looking at is not peak pressure, but the average pressure.

The 257 at a peak pressure of 65k, will have a higher average pressure than a 250 at the same peak pressure.

But maybe that was your point.....

Jason

Jason,

Quite so.
Also, is the same propellant being used in both cartridges - that can make a difference too.
Also are both rifles being fitted with the same length of barrel from the factories?
Velocity can also be effected by altering some variables, if not kept the same.

JEFFE,

The 250 Savage does not operate at a P-max of 66,000 psi like the 257 Wby as per SAAMI.
Based on CIP (as per the QuickLoad program) its P-max is only 52,939 - still way off.


I AM NOT PLAYING GAMES JEFFE, I HAVE ASKED BECAUSE I DO NOT KNOW THE 250 SAVAGE.
IF THE SAAMI PRESSURE IS DIFFERENT THEN WE HAVE APPLES AND ORANGES FOR STARTERS, NOT SO?
THAT IS WHY I WANTED IT OUT OF THE WAY FIRST - RIGHT OR WRONG?

Warrior

Jason,
I fully understand all possible answers re 250 v 257 .. its NOT average pressure, it is WORK - changes in time, pressure, and volume. do you play golf? if your first 3 shots are hard hooks into the woods, your next 3 hard slices into the water, you don't average in the middle of the fairway.

quote:

Originally posted by Warrior:
But I still do not know for sure that the 250 Savage operates at a P-max of 66,000 psi
like the 257 Wby as per SAAMI.


I AM NOT PLAYING GAMES JEFFE, I ASK BECAUSE I DO NOT KNOW THE 250 SAVAGE.
CAN YOU GIVE US THE SAAMI PRESSURE FOR THE 250 SAVAGE?..
WARRIOR

Chris
GET OVER IT - assume the savage is loaded to 65k psi .. OR, if it helps you get around this.

compare savage top loads to weatherby starting.

AtFQ - as it totally disproves your position, you wont. You'll continue to fight the question, rather than provide an answer.

quote:

Originally posted by jeffeosso:

the data CLEARLY shows non-linear RANGE of results, FITTED to a straight line.

Right again. alf's post was a total waste of time reading.

quote:

Now, Chris, stop playing games, and answer my question.. why does a 257 weatherby go FASTER at the SAME pressure than a 250 savage (don't play CIP games, sir, if you are fit to answer the question, then you can accept the parameters)

I realize Jeffe knows the following. For those of you who think warrior can actually answer this without copying something from someone else's material

Yea, alf and warrior should write a book together. Should be the most Plagerized, Illogical trash ever put to print.

quote:

Originally posted by Warrior:
Hot Core,

You obviously understand everything without having to read or study anything - not from books nor from your peers or those before you, like you aquired all your knowledge prior to birth.

Attacking people like you always do does nothing for your reputation. It would be far better to share and teach and take people with you rather than to belittle and demean them in a condescending way.

Warrior

Hot Core,

Your arrogance is the product of disrespect for other people and the luxury of distance of not being in front of people to adjust your attitude.

Warrior

Chris,
why do you refuse to postulate an answer?

of course, you could assume a weatherby starting load is the same pressure as a 250 sav max SAAMI load... and there's still a huge difference.

why? even alf's presented graphs show a broad range of results, greatly pencil whipped to align with a concete

quote:

Originally posted by Warrior:
Your arrogance is the product of disrespect for other people and the luxury of distance of not being in front of people to adjust your attitude.

Warrior

keyboards seems to bred internet ninji ... and he hardly holds the patent for that

quote:

Originally posted by Warrior:
Hot Core,

Your arrogance is the product of disrespect for other people and the luxury of distance of not being in front of people to adjust your attitude.

Warrior

quote:

of course, you could assume a weatherby starting load is the same pressure as a 250 sav max SAAMI load... and there's still a huge difference.

Jeffe,

I do not want to make that assumption because then I will be speculating and I do not use nor know these cartidges. That means I do not know the velocities nor the pressures.

I stick with one rifle and one cartidge to make my observations in terms of how the velocity will go up as I step the load up, and pressure will follow the same trend within reasonable limits within the min and max published loads.

That way most other things stay the same, like the type of powder, seating depth, bullet, chamber & barrel. I don't like comparing it with another rifle or another cartridge where there is a multitude of differences.

This is the practical use for me, and that is all that matters to me.

Warrior