Many experienced handloaders here will already know this, but at the range last weekend I came across such a good illustration of this concept that I thought it might be beneficial to describe.

I fired the first loads though my 338 Edge this past Sunday. I looked around for data and I heard everything from 100 to 103 grains as the go to load with RL33 and 300 grain bullets. Well, that wasn't really specific enough for me so I went to Quickload. QL has the 338 Edge in it's database along with RL33 and the bullet I was using--the 300 grain Sierra Matchking. This was my first time with RL33 and my first time with this rifle, so I was really starting from zero.

The goal was to shoot 2850ish fps from my 29" barrel, so I started with 97 grains of RL33 which QL said would give me 2735 fps and 54,442 psi--a plenty safe starting load. My max test load was 101 grains, which QL said would give me 2854 fps and 63,267 PSI. The general accepted SAAMI max for modern cases in modern rifles is 65,000 PSI, so it looked like everything was good and I was being a touch conservative with my loads. NOTE: The powder charge range I chose is similar to what I would have chosen if I had a loading manual with the data in it.

So I went to the range and set up the Oehler 35p Chrono. I bore sighted the rifle at 100 yds, shot one round, adjusted the scope, shot another round, and got ready for groups.

The 97 grain load gave me 2869 fps with an ES of 15 and no pressure signs (no sticky bolt lift, flattened primer, ejector marks, etc). The velocity was more than 100 fps over than what QL said to expect. Now some would think "Great!! I have a fast barrel" and would have happily loaded to max and even over if they didn't have any pressure signs. That would be a very bad idea.

Here were the velocities of my loads:

RL33, 97 grains: 2869 fps (ES 15)
RL33, 98 grains: 2872 fps (ES 8)
RL33, 99 grains: 2879 fps (ES 21)
RL33, 100 grains: 2905 fps (ES 13)

I didn't shoot the 101 grain load. There still weren't any pressure signs on the brass or bolt lift with the 100 grain load, but 2905 fps was as fast as I was willing to push things, and I expected it was at if not a little over 65,000 psi.

One sign of exceeding max pressure is a spike in velocity. In my experience that will often show up before any other pressure signs. Note that between 97 and 98 grains, velocity only went up 3 fps. This makes sense as one grain of powder in cases of 75 grains capacity and up just doesn't make much of a difference, and that is especially true in a 113 grain capacity case.

Between 98 and 99 grains velocity increased 7 fps. Those very low increases in velocity, along with the low extreme spreads, gave me confidence I wasn't at max pressures. 100 grains jumped up 26 fps over 99 grains. That isn't a huge spike, but it did make me suspect I was at the max, maybe a tiny over. I'll bet money 101 grains would have yielded a 40-50 fps increase in velocity.

So I went back home and opened up QL to try to find the pressures of my loads. To do this I adjusted the powder charge in the program until I matched the velocities I had obtained. Why? In general, to propel a given bullet through a given length barrel with a given powder charge with a given bullet seating depth in a given capacity case, it is going to take a given amount of pressure. Sure, there can be small variations due to minute difference in bore size and barrel smoothness. However, the velocity obtained is an solid indication of the pressure generated, even if the powder charge is less than predicted.

The bottom line is in order for a 300 grain SMK to achieve 2869 fps from my 29" barrel in a 338 Edge with RL33, it's going to require very close to 64,700 psi--even though it only took 98 grains to get that pressure.

Turns out the 100 grain load yielded approx. 67,500 psi--which is indeed a little over SAAMI max. No, the world won't like end in a modern bolt gun at that pressure, but case life will be shorter and the margin of safety is reduced since the pressure curve is exponential from that point.

Because this is a long range rifle, and an extreme spread of 8 fps is where it needs to be for a 3-shot group, I will work with the 98 grain load. I had the bullets at .010" off the lands and I will increase seating depth, expecting to get best accuracy at .030 to .035". This increase in seating depth will cause velocity and pressure to drop off a bit--I just hope the ES doesn't increase as well.

Yes, I realize the pressures and velocities from Quickload are just estimates, but they are more accurate estimates than what we get from a loading manual. In addition to powder charge, QL can account for actual case capacity, actual barrel length, and actual bullet seating depth.

DISCLAIMER: The loads I posted here may not be safe in your rifle. Always start low and work up. If I had known the velocities I was going to get, I would have started with 93 grains, then increased to 95 grains, then 97, 98, 99.

One final thought. If you are developing loads and plan to go anywhere near maximum velocities, a chronograph is a must.

Chronographs do not read pressure. You are extrapolating, interpreting, correlating (to published data) or some other word. You may be adept at using your own chrony in a way that is safe to you. Some less talented friend could take what you say for granted/"gospel" and come to harm. Interesting investigation on your part and very well written up.

Cheers!

Nice analysis, but I would not take it to offer logical conclusions; you can make data and information mean anything you want. Chronographs do not read pressure (as stated above), nor does QL give perfect data; too many variables.
If you had no "signs" of high pressure, then how do you know what it really was? I have used QL too, and sometimes it does not react to a particular combination of rifle, brass, powder, etc.
If you really want to know pressure, you need to get a piezo system and glue it to your barrel, and your PC. A chrono won't tell you pressure.

You guys missed the main point. Maybe I did t state it well enough. My way is much more conservative than what most do.

Many guys using loading data assume they are good to go as long as they don't see any signs of pressure on the brass--that is wrong. They assume that if they achieve 100 fps over the max published velocity, they are within safe pressures as long as they don't see any pressure signs on the brass. That idea is incorrect. We cannot exceed a given velocity level with exceeding a given pressure, so if we are 100 fps over the max velocity we are over the max pressure regardless of how the brass looks. Brass can withstand as much as 80,000 PSI and not show any signs of pressure.

In my situation above, the chronograph kept me from running way too hot of a load. I knew that velocity corresponds to pressure, and if I exceed max velocities I am exceeding max pressures. Using my way adds another pressure reading tool. Velocity is a MUCH better indicator of pressure than signs on brass. There is no ballistic free lunch.

And like I said before, Quickload IS only an estimate, but it is a WAY more accurate estimate than a loading manual.

The bottom line is to use a chronograph, and understand that if you are getting higher velocities than published with a given bullet and powder with given a barrel length, you are also getting higher pressures.

I do not agree with your logic; if we had steel cases with screwed in primers, we could go to much higher pressures than we can with our primitive brass cases and primers. We could then go as high as the steel in the rifle would allow. Case in point; that is how we get 4800+ FPS in our tank cannons; we use steel cases and steel primers (electric). So we can go to 100,000 psi easily. I submit that the only limit in any particular rifle is the brass case and primer, and each rifle has it's own limit. There are ballistic free lunches, and they take the form of different barrels; as evidenced by the differing loads they will handle before exhibiting "high" pressure.

Yes, the limit is the brass case and primer, and velocity often tells us first when we reach those limits. Using your approach I'd still be running 74,000 PSI loads and wondering why cases were only lasting two firings. I see that as error. Maybe you don't.

So do you load up a break action double until you see pressure signs on the brass? I don't. I know I can safely get 2100-2150 fps with 480-500 grain bullets in my 459 450 NE and keep under 45,000 PSI. So I won't exceed those velocities regardless of how the brass looks.

You just blew your whole argument and premise by using the word "often". The real rule should be: "sometimes". I have two 257 Roberts which take vastly different load levels for vastly different velocities. Your method would not accommodate that scenario.
You know as well as I do that you don't load double rifles the same as bolt actions. You can't read brass and primer pressure signs at those low pressures and double rifles are certainly not made for hot rodding. What make is your 459 NE??

Where did you ever get the idea that I am saying the same load produces the same velocity? In fact, that is the exact OPPOSITE of what I said. I am saying the same velocity will produce the same pressure with the same powder. For example, one 257 with a 22" barrel may take 50 grains of Hxxx to get 2700 fps with a 117 grain super bullet and another 22" barreled 257 may take 54 grains of Hxxx to get 2700 fps with the 117 grain super bullet. If you pressure tested both rifles, you'd find pressures would be very similar
even though the loads are way different.

I am done with this. You either don't understand what I've said, didn't really read what I have written, or you are being obtuse and just want to argue. Your comment on my 459 typo is plain disrespectful. This former 24 yr USAF pilot does not tolerate disrespect and doesn't have patience for obtuseness. I have ZERO need to post on this forum, so I leave you to making all the hot handloads you want.

Thus ends my short experiment in trying to participate in shooting forum.......

Thanks for your service. No disrespect intended; just trying, unsuccessfully, to be funny.
I think I understand your theory; I just don't agree that it is always valid. I could be wrong.
I tried to write and apologize but I see you have blocked me. I am not attacking you; just discussing and relaying my thoughts. Sorry you didn't like them.

How to use a chronograph to "read pressure"

Shooting INTJ down for posting his thoughts on the use of the chronograph has not really thought this one through.

He certainly did not infer that he was measuring pressure using the chronograph nor did he make claims that his method using his gun and laid would equate to a pressure value in my gun or anyone else's gun.

The basic tenant of how our ballistics system works is that a known charge of powder would result in a specific pressure profile that would result in a specific velocity value for a bullet of specific sectional density. ( This is called Piezometric efficiency)

It thus stands to reason that if one were to know what all the variables are in the equation that having knowledge of the velocity of a specific bullet of known sectional density that the pressure value could be calculated to reasonable level of accuracy and validity.

This was after all the basic tenants of classical internal ballistics. It formed for the better part of the 20th century the basis of how guns and gun systems were designed.

The second efficiency is known as the balletic efficiency.

Simply put BE refers to the V/C ratio
Ie velocity to total charge ratio expressed as FPS per gr of powder

By using your chronograph and your now gun and loads it is possible to plot trends in V/C by plotting these on a graph a trend can be established which is valid for your gun and your loads. Deviation from the trend is an indicator that pressure is changing ! it does not measure pressure, it gives you no value of pressure it's simply a trend for your gun, your load.

But in this lies the value:

This can then be compared against the trends of that cited by a load manual or load program for the same bullet and load. These are usually accompanied by approximated pressure values (either calculated or actually measured)

I also use the chronograph when developing loads. Trouble is that I dont trust my results 100%. I use it to compare my loads with loaddata and sometimes factory ammunition.

Velocity spikes are not connected to max pressure.

What is amazing to me is that modern reloaders summarily dismiss the use of the chronograph and do not realize without the chronograph we would have none of the data we find in common reloading manuals available to us.

Come to think of it likely no modern guns and components either.

The two most important discoveries in gun system design was the discovery and use of the chronograph ( the Boulenge chonograph or otherwise known as the screen to screen chonograph) and the second was the discovery and use of the copper crusher.

These two discoveries took ballistics from a theoretical science to a practical science. It validated the authenticity of theoretical agument.

Today these have been largely displaced by the doppler radar and the piezo electric transducer.

Most of the data presented in load manuals and a computer based manuals are actually theoretically derived using formulae that hail from classical ballistics theory.

They dont physically test each and every load increment. Select Points on a graph are tested and validated and data inbetween cames from approximation using empirical formulae.

For instance CIP use this method when "wildcat" cartridges are submitted for proof. They dont have proof barrels for each of these cartrdiges so what they do is to subject chronograph data to empirical mathematical analysis to a set formula and they come up with a proof pressure limit. It is valid within the understanding of how they derive their data and they accept it as a matter of law.

One could argue that WW2 was won on the ground using this method. John Corner, a british theoretical mathematician who wrote the book the Theory of internal ballistics of guns published in 1950 could be hailed a a hero of WW2 because he gave the Allies the means of defeating German armour with inferior guns.

if it were not for his applications of theory the undergunned allied tankers and anti tank gun crews would not have had the tools necessary to defeat German armour.

quote:

Brass can withstand as much as 80,000 PSI and not show any signs of pressure.

INTJ,

I agree with you that the chronograph is a very useful tool in working-up loads; and, another adjuct in looking for excessive PSI.

Velocity does correlate with PSI - that is, increasing PSI results in greater velocity.

I also use QL to estimate PSI and velocity correlation for a given cartridge.

For me, the problem with QL is the mysterious "weighting factor" and "shot initiation pressure", which are both variables that change QL velocity/PSI correlation output significantly. OAL also significantly changes QL output. Temperature should also be considered in your calculations.

If you figure out all these QL variables and how best to adjust them, I'd like to hear from you.

You also make the comment that brass can withstand 80,000 PSI without any PSI signs.

That has not been my experience.

I would suggest to you that typical rifle brass begins to show measureable PSI signs at ~65,000 PSI, usually in the form rapid loosening of the primer pockets after only 3 or 4 firings. A hand held priming tool is good for feeling this loosening.

Finally, what is excessive PSI? How much risk are you willing to take? The case is the "PSI-limiting" item in high performance reloading. The case will fail and show early signs of failure long before your modern steel first-rate bolt-action rifle fails, which by the way should be able to take ~150,000 PSI easily.

Yet, I want to avoid a blown primer pocket and/or a stuck case. I'd hate to see the trophy of a life time disappear over the hill, because I had a stuck case and couldn't reload or have injured my eyes because of escaping gases from a blown primer pocket. (Yet, I've blown primers without hurting my eyes, but I wear glasses; and, the cases have never been stuck.)

From what I can glean from the literature and following numerous discussions with Speer, Sierra, Hornaday, and Nosler ballisticians, blown primer pockets occur with regularity when you approach 75,000 to 80,000 PSI. Lapua claims their cases are "good" up to 67,000 PSI, although I'm not quite sure what they mean by that.

AIU

quote:

They dont physically test each and every load increment. Select Points on a graph are tested and validated and data inbetween cames from approximation using empirical formulae.

I'm siting here with a Hornady II manual on my desk. It actually states that ALL of the IMR (at least at 1973) have the same energy per gr. That faster powders simply had a different grain size and coating. So they could use the same velocity vs gr of powder curves since they were parallel. At least Hornady assumed the relationship at least for IMR powders was liner. They simply took one load to determine were to draw the new line. Then took max pressure from the curve or a full case whichever came first. Other powders they plotted as liner but not parallel.

I love my chronograph. Did eliminate some bragging rights when I first got it.

Don't know if I'd say it measures pressure but, it does help me try and better "guess" at what is going on. I also use QL to try and adjust data. I agree with AIU I sure wish I could better understand all the adjustments it allows me to play with. I try and use a KISS principle and adjust as little as possible other than capacity and OAL.

I have blown primers in my younger and aggressive days. Had primers fall out after two loadings. Now days that extra 20fps isn't worth it.

In the very early days of Handloader magazine, Handloaders Digest and the NRA magazine they actually had real life professional ballisticians contribute articles. People like Kent and former directors at White Laboratories and the Aberdeen Proving grounds.

I have an article from the first edition of handloaders digest detailing how the home reloader can use a chonongraph and esitimate where they are in terms of pressure in their guns.

I made the mistake of digitizing all my paper articles from a huge collection of original magazines that I collected over years and now my new Apple with its new software will not retrieve the stuff from my old data files. The new programs are uable to read and proccess the older file formats !

quote:

The new programs are uable to read and proccess the older file formats

Isn't technology great.

Had some similar issues myself. Had to take files I had scanned and print them out from my old PC so I could rescan them on my new one. This time I kept the paper copies.

There is a direct correlation between pressure and muzzle velocity. It isn't even arguable. I think the OP makes a very valid point.

Very interesting. I have talked about using a chrony as a "guide" to determining pressure, ie, if the book sez xxx velocity gives you xxx pressure and your load is going that fast, then you can assume your pressure is close to what is published regardless of what your wgt of charge is.
Seems each time, however, I've been shouted down with the same arguments. But it works for me and I'm comfortable with it.

quote:

How To Use a Chronograph to Estimate Pressure

Only the title wasn't stellar. Good report otherwise, and just how I also use a chrony to compare results.

INTJ, I have one question for you.

What would your load/velocity chroney readings show if you had used the recommended Cartridge Overall Length for seating depth?

Your experiment seemed to show that seating .010 off the lands will cause higher velocities. I would contend that any comparisons between your results and the load data used are null and void because you changed a very important variable.

I am not trying to pick on you, just pointing out that you mentioned the seating depth as .010 off the lands, acknowledged that it would change pressure when you start seating your bullets farther off the lands, and left it at that.

Seating depth is a huge variable with regards to pressure, velocity, from a given load.

quote:

Originally posted by mike_elmer:
INTJ, I have one question for you.

What would your load/velocity chroney readings show if you had used the recommended Cartridge Overall Length for seating depth?

Your experiment seemed to show that seating .010 off the lands will cause higher velocities. I would contend that any comparisons between your results and the load data used are null and void because you changed a very important variable.

I am not trying to pick on you, just pointing out that you mentioned the seating depth as .010 off the lands, acknowledged that it would change pressure when you start seating your bullets farther off the lands, and left it at that.

Seating depth is a huge variable with regards to pressure, velocity, from a given load.

Good point, which is exactly why you start loads a couple grains under max when seating out near the lands, which is where I always start. Case in point....7RM 160 AB's, .005 off, 3050fps, RL 22. By watching your chrono, you obviously know that getting those velocities, you are nearing max pressures, otherwise you'd be running 2900 fps. Move the bullet in, to .025 off for instance, velocities will go down as well as pressure with the same powder and charge. I've reloaded that brass for the 6th time now, no problems.

Just as a point of interest to those who wish to use a chronograph as a means to determine pressure.

The proportionality between pressure and Velocity is not simply a case of V = P

The proportionality (and it is linear) lies with the following assumption.

In a frictionless system

E = AsP
where E = kinetic energy of the bullet at egress
A = cross sectional surface area of the bore
s = length of bullet travel in the bore
P = MEP = Mean effective barrel pressure.

MEP is not Peak chamber pressure ! The ratio of PCP and MEP differs based on the piezometric effieciency of the gun load combination and is related to the Sectional density of the projectile.

There are other proportionalities some linear some exponential

For barrel length and velocity for a given sectional density of bullet, this is linear.

Or the V/C ratio, this is exponential.

We can plot on a graph the proportionalities of published lab tested loads ( the old IMR load data booklets gave these results) and then superimpose our own measured data from the chrono on these and see where we lie.

The caveat is that we have to to convert our measurements to the correct units of measurement before applying them to the graph.

The proportionality is Joule to unit of pressure and not m/s to unit of pressure.

I am curious about something in regard to the loads. It seems to me that with the loads listed with a gain of only 3 fps between loads one and two and 7 fps between loads 2 & 3 that the maximum efficiency of the case with RL33 had been reached, that point of diminishing returns. And, that the velocity spike between load 3 and 4 indicates that load #3 is the sensible max. I understand that the increase in charge is essentially 1% and not that great but I would have thought the increase in velocity more.

In defense of my ignorance, if ignorance can be defended, I have never work with a cartridge burning that large a charge. Is that small of a gain the norm when burning large charges of powder?

ALF,

Do you have a copy of QL? If so, do you have in-the-field experience with it?

An in depth discussion of its optimal use would be practical and very helpful.

I'm especially interested in the proper settings for the "weighting factor", "start initiation pressure", and for making adjustments to the individual powder variables so as to account for "apparent" lot-to-lot variability.

Regards, AIU

quote:

An in depth discussion of its optimal use would be practical and very helpful. I'm especially interested in the proper settings for the "weighting factor", "start initiation pressure", and for making adjustments to the individual powder variables so as to account for "apparent" lot-to-lot variability.

One of these days I'm going to get several and sit down a READ IN DETAIL the 120 page QL instruction manual.

AIU:

I don't have a copy of QL , I do have Load from a disc on a now defunct PC , It does not work on Apple.

You do need to know how the program for QL is derived mathematically to account for variations in conditions.

What we do need to understand though is that all of the consumer grade load programs are derived from certain pre set assumptions and theoretical mathematical theorems that do not account for what can be seen as the "minor contributing factors" of pressure.

All either over or underestimate pressure based on the premises that are preset.

As an example Powley assumes a frictionless barrel, it presets the load density in the input and it is based on the performance derived from the use of IMR propellants.

More robust ( and complex) industrial programs exist primarily for the design of cannon and larger bore weapons.

quote:

However, the velocity obtained is an solid indication of the pressure generated, even if the powder charge is less than predicted.

First of all intj makes a superb post on this subject. His reasoning and decision making is among the best I've read on this subject. He has used a lot of inputs to his decision making.....not just the chronograph.

...it reminds me of the days when Hotcore posted here.....

Lets take this quoted statement apart...ok?

It's reasonable to assume that factory stated velocities are about as much as any factory could muster inside the SAAMI specs. It's also reasonable to assume any factory has pressure testing equipment. It's therefore reasonable to assume that if one actually reached that velocity in his handloads that his pressure is close to or at least equal or higher than the factory loads.

Here is the trick to that statement.....It's absolutely not reasonable to assume that if your velocity is lower than the factory loads that your pressure is also lower than the SAAMI spec.....it might be....but lets face it....you're guessing!

The statement that pressure and velocity are related is only marginally true.....Velocity is related much more to the area under the time-pressure curve than to pressure alone and this has a lot to do with the burn rate of the powder used. Essentially, if one uses a "too fast" powder he may reach the 65,000 PSI limit but the velocity will be substantially under the factory loadings.

It boils down to this....using a chronograph is a good tool in handloading.....it gives us a piece of information. PERIOD! How you deal with that information in the context of all the other information you have collected is up to you but to assume that you can keep adding powder until you reach the "factory" velocities is just heading in a bad direction.

BTW....case head expansion is something I still believe is a good piece of information and worthy of adding to your tool box....like the chronograph....it can send you a message that you're heading for trouble before you get there.

Vapodog:

Area under Time pressure curve = piezometric efficiency of the gun.

The shape of the curve determines the design of the gun and coupled to this also the performance of the gun.

The wilful manipulation of "position of burnt" by choice of specific propellant types determines what kind of precision you can expect form the gun system. That part of precision that is brought about by velocity scatter between shots.

This is not that apparent in our small bore shooting systems but when the guns get bigger this becomes a central issue.

quote:

Area under Time pressure curve = piezometric efficiency of the gun.

ALF, I'm surprised you don't have working copy of QL, given your interests. Why not get one and engage in of discussion her of QL? This would be very helpful. Regards, AIU

Vapodog:

go check it out !
The term was first coined by a dude by the name of Zaroodni. it is covered in Corner's Theory of internal ballistics of guns

The shape and hence to size of the area under the curve determines this effciency.

The math derivation for this reads:

Eta = MEP / Peak pressure

In using the derivations needed to understand relationships between velocity and pressure to be able to make sense of our chornograph value as it pertains to pressure we only have the MEP to kinetic energy ratio avalilabe to us. We have no idea of peak pressure. Not unless we employ the use of a calibrated piezo or copper crusher.

You can have two different pressure time curves with different shapes fired from the same gun ( using different types of powder) both can have the same velocity. What will differ though is where within the gun pressure is most evident. ie where it peaks and drops off.

The effect of this is that it has a influence on inter shot velocity scatter which in turn has a profound effct on time of flight in long range shots ie shot precision at long ranges.

Short range high velocity anti tanks guns are typically high effciency guns and 155 mm long range pieces are low efficiency guns

Way too much high tech verbiage for me. As I said, it works for me. Maybe I'm kinda like the bumblebee, I don't know.
As far as there no being a relationship between pressure and velocity, I don't believe that. When the big cartridge companies order up a ton or so of powder, the guys in the white coats determine what the burn rate is and how much would need to be dumped in a say 30-06 to achieve a certain pressure. They relay this to the guys in hard hats who start loading ammo.

ALF, all the math, formulae, and the like don't have much practical value to the VAST majority of folks reading this forum...it's almost a waste of time, unless you're teaching a college course in Theory of Internal Ballistics.

If you want to really help us, GET A WORKING COPY OF QUICK LOAD, use it in the field, gain experience with it, and begin a discussion of how best to apply it for the average reloader reading this forum.

QL is available to all of us and is a practical program to have.

Regards, AIU

AIU:

You are so right but it is sadly in my nature to read up and explore that what I am interested in.

Now what prompted my contribution to this was simply to come to the defence of INTJ who started this thread.

Some were ready to run him off this board and did so because he dared mention pressure and a chrono in one sentence ! big NO! NO ! on AR when HOTCORE was still around

So perhaps open minds are in order not so?

But come to think of it you have a copy of QL what stops you from finding out how the thing is put together and how it works And I do not mean this in a derogatory way at all. I too would be interested to know what they have a critical steps in the mathematical formula and especially where the failings are because trust me there are numerous short comings.

I will bet you that you would need to wrestle with the theory of internal ballistics and more. Perhaps the chemistry of propellants ? now there is a subject that is difficult to get around. I have tried and it's daunting.

My wife has said that she is certain that homeland security have me on the radar because of the searches I conduct in the defence open archives

Okay . . . I'm a guppy in such matters, and am willing to ask a Dumb Question (which may already have been answered).

Has anyone actually plotted velocity vs pressure, other than than the folks who publish reloading manuals?

I'm thinking in 0.5 grain increments, for any combination of bullet weight, irrespective of caliber, bullet manufacturer and powder?

If this is a dumb question . . . I plead guppy-ness.

UPDATE: Edited for clarity.

quote:

Originally posted by ALF:
AIU:

But come to think of it you have a copy of QL what stops you from finding out how the thing is put together and how it works And I do not mean this in a derogatory way at all. I too would be interested to know what they have a critical steps in the mathematical formula and especially where the failings are because trust me there are numerous short comings.

I will bet you that you would need to wrestle with the theory of internal ballistics and more. Perhaps the chemistry of propellants ? now there is a subject that is difficult to get around. I have tried and it's daunting.

My wife has said that she is certain that homeland security have me on the radar because of the searches I conduct in the defence open archives

ALF, as diplomatically suggested by Ramrod340, I should peruse again the - often nebulous - instruction manual, but I still struggle with certain critical variables and how to properly adjust them - that is, "weighting factor" and "shot initial pressure".

I think I understand the theory behind these factors, but suggest a discussion with somebody unafraid of basic physics or chemistry and with an engineering/scientific approach would help convert theory to practical application.

QL provides default values, but with QL one can adjust these two variables, along with changing OAL, and get QL to spit out the velocity/PSI data you want.

Using a program I can manipulate makes me nervous, and my brain says...AIU, if you do this, you better know what you're doing.

I called one QL "professional", but I don't think he was as knowing and he considered himself. IMO, he couldn't explain how to properly use the "weighting factor", or for that matter the theory behind it.

I came away thinking the "weighting factor" is really a "fudge factor", built into the program, to make QL data fit actual pressure barrel data. This is kinda scary.

Regards, AIU

quote:

as diplomatically suggested by Ramrod340, I should peruse again the - often nebulous - instruction manual

I'm sure not pointing fingers at anyone. Because when you point a finger 3 more are pointing back at you. As I was informed by my grandson a couple years ago. Smart kid.

I skimmed the 120 page manual quick enough to run the program when I first got it. I know I need to sit down and read in detail what changing the options do. I know enough to tweak it a LITTLE but I really need to learn exactly what my tweak might be doing to other answers. Seems like I always find something else to do besides study. Seems like I might have had the same issue in college.

Anyway have a good one.

So here is a question that has been on my own mind.

The Short mag followers claim short mags are better than their now aged long versions ?

So by this i ask:

If we take say a 300 win mag, shorten and fatten the case so that we have a short mag with the same case capacity as the original would our short mag give more , equal or less velocity than the old version ?

Now the barrel length is the same the total bore + chamber volume is the same.

What say ye on this one? and how would be other than actually shoot such as beast get to an answer?

quote:

Originally posted by ALF:
So here is a question that has been on my own mind.

The Short mag followers claim short mags are better than their now aged long versions ?

So by this i ask:

If we take say a 300 win mag, shorten and fatten the case so that we have a short mag with the same case capacity as the original would our short mag give more , equal or less velocity than the old version ?

Now the barrel length is the same the total bore + chamber volume is the same.

What say ye on this one? and how would be other than actually shoot such as beast get to an answer?

Is this the sample table in the Canned Worms aisle at Sam's Club? LOL!!! A whole lot of speculatin' going on!!

yes mike it is!

But it's directly related to the thread in hand because it deals with the why and how of how velocity is derived and how it relates to pressure and where it is generated relative to the muzzle.

it links up to Hornady's new line up of new ammo offerings.

For the same caliber they have low velocity low recoil options, "normal velocity" and high performance ammo. How do they do that and still be safe ?

They have only two options, manipulate piezometric efficiency and / or manipulate ballistic efficiency.

Every barrel ie (volume wise) has ballistics limits. This is set by a pressure ceiling. If you load to low you may hit or worse exceed it ; if you load high you definitely hit that ceiling.