Pressure signs and the real world

[AtlLaw]

Reading another thread in the forum about pressure signs got me thinking.  (I know, I know...    )
Before chronographs became affordable we accepted the published velocities or guessed based on them.
I made a comment on the other thread that we would not have any idea of the pressures our loads are actually running until someone came out with an inexpensive PSI o'meter.  Then I remembered something.

Now, I haven't used a ballistics program since the one I was using went out of production; Lock, Stock and Barrel I think it was.  But I have heard that there is a program out there, could it be "Load by Disk?" that actually gives a chamber pressure for the load you key in.  If there is such a program:
1. has there ever been any study done on the accuracy of it's pressure predictions?  And;
2. if it is acceptably accurate, is it possible we could make notes of ALL the traditional signs we may observe while working up loads and, with a large enough sample, see for ourselves if there is any correlation that could be made between pressure and the traditional indicators?

As an aside, if the program IS accurate, we have our PSI o'meter and I would LOVE to know what pressure I'm running in my Handi with my favorite 7x57 load!

Getting back to the indicators, don't jump on me with "how flat is flat" and How hard to open is hard" questions.  This is just an academic thought.  And, I've always believed that hand loading is a lot like the law.  There's not much out there that somebody hasn't thought of and that thought researched by somebody.  Does anyone know if that is the case here?

[Dave in WV]

Norma ammo isn't loaded down for the 7x57. I'd fire some of it in your rifle and use the fired cases for a control. One thing I've noticed when firing max loads is the lack of carbon on the case neck. Factory ammo will usually have some discoloration on the neck near the case mouth. When I see no discoloration or very little discoloration on the neck I back off. I load .38SPCL, .357 mag, .44 mag, 45CAP, .243, 7mm-08, & 30-06 and use this rule of thumb for all my reloading as well as flattened primers and other signs.

[beemanbeme]

The fact of the matter is we don't have personnal PSI'ometers.  But we are told that the books are worthless and empirical observations are meaningless.  Too, regardless of how vast the data base, somewhere in the preamble would be the statement: "each rifle is a law unto itself and generalizations should be made with circumspection." which means that data would be suspect.
And so, the question begs to be asked:  How have we been able to muddle thru for oh say the last 100 years or so and thru several gazillion rounds of good safe ammo using the load books and empirical means?  There have been exceptions but they could usually be traced to faulty equipment or folks in the shallow end of the gene pool.  
What are we to do?  Quit reloading?  Nay saying everything that comes down the pike acchieves nothing if solutions aren't offered.  

[Castaway]

The only solution to finding your pressure is to send them off to someone that has a meter that can gauge reality.  The "old" methods of comparing case head expansion with a factory round against a reload have been proven worthless.  Ditto for hard extraction, especially straight walled calibers.  You can exceed pressures by a dangerous amount and still get easy extraction with them.  Flattened primers are indicative of excessive pressure, but by the time you get to that point you have passed what is safe by a good amount.  Low pressure is indicated by carboned-up case mouths since the case isn't expanding to seal the bore, but that's not necessarily a bad thing, but.... stay away from such loads if shooting jacketed bullets.

[LaOtto222]

AtlLaw - 1st of all I love to theorize the what if's. I could go on all day with someone of decent knowledge or an open curiosity. That is the main reason I joined up in GBO. I realize that is the purpose of this thread. So I thank you for it.

It sure would be nice if we could crunch some numbers and calculate pressures. I am not sure there is any thing like that. All of the ballistic programs I am aware of deal with external ballistics, not internal. If there is such a program out there some where, that is reliable, I would snatch it right up. I hate fling by the seat of my pants when developing a load. I really doubt that there is a program like that. As was discussed in the previous thread you mentioned, there are just too many variables involved. The vessel (case) is dynamic during firing. It changes volume when it is fired. How much it changes, depends on the chamber dimensions. Every gun is different, even with in the same model number. That is just one variable and it would be difficult to determine. You would have to know the volume of the case when it is stretched to it's fullest. Afterward, it shrinks back down some. I like the way you think, but I seriously doubt there is any thing that would be reliable.

Talking about PSI O' Meters - you never know...I remember when chronographs were hard to get and they were very expensive. Now they are cheap and plentiful. Could a cheap PSI O' Meter be in our future? Tape a strain gage or two on the barrel that feeds a little box that pops out what the psi was???

[steve4102]

It sure would be nice if we could crunch some numbers and calculate pressures. I am not sure there is any thing like that. All of the ballistic programs I am aware of deal with external ballistics, not internal. If there is such a program out there some where, that is reliable, I would snatch it right up

  There are a few "Internal" ballistic programs out there.  Of course they are not completely reliable, only guidelines similar to the paper manuals.  QuickLoad is considered one of the best.
http://www.neconos.com/

  I have QL, if you have any questins or would like me to run some calculation, ask away.

[LaOtto222]

QuickLoad looks interesting, but they have a warning ; "Results without any guarantee on usability!" I do suppose that a warning would have to be issued like this for liability reasons. Do you know if anybody that is independent and reliable has made any comparisons using this calculated data and actual pressure readings to see if there is a real comparison? I realize that the information you plug in needs to be accurate, but there are so many variables. I do not see how pressure can be calculated and relied on, beyond just being a curiosity.

[AtlLaw]

There are a few "Internal" ballistic programs out there.  Of course they are not completely reliable, only guidelines similar to the paper manuals.  QuickLoad is considered one of the best.
http://www.neconos.com/

AhHA!  I'm not crazy after all... well some people say I am, but the voices say I'm fine...    Now that you say "QuickLoad" I remember that was the one.  So, we got a program... now we need to come up with some testing parameters.

Oh BTW, I'll dig up that 7x57 load and give you the particulars!  Thanx!

QuickLoad looks interesting

I'ma gonna look at it also.  I spent a long time yesterday thinking about all the possible variables involved in a mathematical formula created to calculate pressure, and while I think it's possible to come up with such a formula, I believe that so many assumptions would have to be made to limit the virtually infinite permutations of the variables that the results would be as viable as case head measurement, flattened primers, etc.  Maybe that's the reason for the warning, which I interpret to mean "the results are worthless for any use."

I can't believe that no one has done a study on this function.  You think that some rag writer would, unless they are worried about losing advertising income...

So, for the good of the group, who is going to spring for the cost of having a ballistics lab measure the pressure on a bunch of our favorite loads?

Oh, Beemanbeme.  You're absolutely right of course, but I left the argument of the reliability of pressure indicators to the other thread, not wanting to hijack it and all.  We'll keep loading but I don't think you're really a loadaholic or maybe just not anal enough if the inability to determine the PSI of your loads doesn't bother you!     BTW, I also feel that shallow end of the gene pool need a good cleansing... and often! 

[beemanbeme]

Well, this seems to be the latest hot button. As you can go into any room and there is at least one looong thread about this subject.  And everybody has an opinion.  Castaway hangs crepe and forecast doom but he doesn't answer the question of how have we been able to skirt the edges of disaster for so long using the very methods he (and others) discry?
  I guess I'll just have to be like the bumblebee.  All of the "experts" say he can't fly but noone's bothered to tell him so he just goes happily on. I guess that'll be me. The reloader with the big smile on my face. Grinnin' and shootin' whilst you folks sit on the cellar steps worrying about the hatchet that might fall on your head.................   (that's an old fable for you young'uns)

[steve4102]

Oh BTW, I'll dig up that 7x57 load and give you the particulars!

  QL requires a few "particulars".  You can go with the generic "maximum case capacity" of H2O or you can be more precise and use the actual grains of water from a fired case.  You will also need the COL, bullet type, brand/weight and of course powder choice.  Barrel length is important for velocity, but not so much for pressure.  QL does not care about primers or twist rate.

  Here is what one of the pages(windows) of QL will show you.  This a 300WSM with 165gr Nosler BT, 24 inch barrel, 2.85 OAL and 760.  As you can see QL has a charge of 65.5gr of 760 at 3083fps and 60,901psi.  My Lyman 48 has this load listed at 65.5gr 760, 3067fps and 61,400psi.  Pretty darn close.  Nosler #6 has this load at 66.5gr 760 and 3171fps, again pretty darn close.  It's a great program, but like anything else always double and tripple check your data.

Cartridge          : .300 WSM (CIP)
Bullet             : .308, 165, Nosler BalTip 30165
Cartridge O.A.L. L6: 2.860 inch or 72.64 mm
Barrel Length      : 24.0 inch or 609.6 mm
Powder             : Winchester 760

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

-20.0   76    52.40   2473    2240   31601   8693     90.3    1.505
-18.0   78    53.71   2534    2352   33743   8965     91.6    1.466
-16.0   80    55.02   2595    2466   36029   9227     92.7    1.427
-14.0   82    56.33   2656    2584   38472   9480     93.8    1.387
-12.0   84    57.64   2716    2703   41081   9722     94.8    1.344
-10.0   86    58.95   2777    2826   43847   9951     95.7    1.305
-08.0   88    60.26   2838    2951   46774  10168     96.6    1.266
-06.0   90    61.57   2898    3078   49894  10370     97.3    1.229
-04.0   91    62.88   2959    3207   53221  10558     98.0    1.193
-02.0   93    64.19   3019    3339   56772  10729     98.5    1.159  ! Near Maximum !
+00.0   95    65.50   3079    3472   60564  10885     99.0    1.126  ! Near Maximum !
+02.0   97    66.81   3138    3608   64617  11022     99.4    1.094  !DANGEROUS LOAD-DO NOT USE!
+04.0   99    68.12   3197    3745   68951  11141     99.7    1.063  !DANGEROUS LOAD-DO NOT USE!
+06.0  101    69.43   3256    3884   73591  11241     99.9    1.033  !DANGEROUS LOAD-DO NOT USE!
+08.0  103    70.74   3314    4025   78564  11321    100.0    1.004  !DANGEROUS LOAD-DO NOT USE!
+10.0  105    72.05   3372    4167   83901  11382    100.0    0.976  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba     95    65.50   3212    3779   72432  10542    100.0    1.045  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba     95    65.50   2893    3067   48999  10679     93.8    1.233

[AtlLaw]

The reloader with the big smile on my face. Grinnin' and shootin' whilst you folks sit on the cellar steps worrying about the hatchet that might fall on your head.................   (that's an old fable for you young'uns)

Aw cummon Bee!  No body's waiting for a hatchet to fall!  A rifle bolt between the eyes maybe... 
Don't you find this the least bit interesting?  All us old dudes have and will continue to use all the things we've always used and like GB insinuated in his post in the other thread we all develop reloading philosophies that we think are reasonable, logical and work for us.  Others may not agree with them, but that doesn't mean they are wrong.  All of us just keep "Grinnin' and shootin'."  (NOTE: the shallow end of the aforementioned gene pool is excluded from the heretofore identified group of reloaders.)

Now admit it.  Your breath comes in short gasps at the mere thought of knowing the pressure of your hand loads and being able to observe the variances with changes in components!

[AtlLaw]

Steve, that's just slicker then owl crap on ice cream!     I GOT to get me one of them!  How many comparisons can you do with known pressure loads to get some indication of reliability!?  I've got a subscription to LoadData.com and a lot of their loads have recorded pressure... 'corse I got no idea how they measured that pressure...
I'ma gonna run down to my gun room in a bit and dig out all the required info from my records for that 7x57 load!  Oh wait!  I was using IMR 4350!  That's a temperature sensitive powder!  Another variable!     Would the outside air temperature on the day I shot the loads help?   
LaO, what 'cha thin?  (more vernacular...)

[quickdtoo]

I've been working with QL3.4 for a couple months now, from what I learned about it before I bought it, it's very accurate with jacketed bullets, but not so with cast bullets, as Steve noted, I've ran published jacketed data through it and came up with pressures that were very close, but not so with cast bullets that I've compared using Lyman data.

Tim

http://www.neconos.com/shop/?shop=1&cat=2

[AtlLaw]

Coming from you Tim, that's high praise indeed!  You haven't run that BL-C(2) 180 gr. 338/06 load through it have you?

[quickdtoo]

I haven't, but I can, I might even have a fired case Handi!!

Tim

[chutesnreloads]

I remember reading about just such a thing in The Varmint Hunter magazine a year or so ago.He had pressure measuring devices attached to the rifle and if I remember right to a laptop computer.Gave him pressure readings for each shot.That's all I remember but I'll go through the old issues I have and see if I can find it

[Graybeard]

Once long ago I bought a .30-30 AI TC barrel from a former member of this site. With it he included a bunch of bullets he had cast, ammo he had loaded, some empty fire formed cases and some QL sheets with data for the round.

My observations on this were:

1. The ammo he had loaded did not even remotely match the data he gave me for velocity or accuracy.

2. The QL load data was as bogus as a three dollar bill. In many cases you'd not even be able to dump that much powder of those types into the case if you use a sledge hammer to pound it in. Much of the data on those sheets that purported to be safe pressures were as much as 10-12 grains more than is safe in a .30-30 case even tho the AI case adds at most 4 grains of extra capacity as measured by me on the same case before and after fire forming.

You guys can depend on it and trust it if you wish but this old fat boy will never ever believe a QL read out sheet again.

[jhalcott]

  Here's some light reading for you guys!
  http://www.oehler-research.com/wizard.html

[quickdtoo]

QuickLoad is just another tool, not unlike a loading manual, as stated on the opening page of the software, it's not a replacement for proper, safe handloading practices. 

Tim

[LaOtto222]

I asked if anyone had some hard data with correlation between the calculated pressure and actually pressures. I have not seen any yet. Just because you calculate 60,000 psi and a book says 61,000 psi for the same load, still does not mean they are the same or even close. They were shot out of different guns. I was looking for a direct comparison over several different cases and bullet weights. Where they calculated a load, loaded it up and then shot it in a barrel with pressure sensing equipment. I was looking for something like + or -  5% or  it is always 5% -  10% below actual, some thing like that. I really do not think it is possible. Like has been stated before, there are just too many variables, even from one gun to the next. I have found that a tight chamber gives less pressure signs than a sloppy chamber, but that does not mean that they both do not see the same pressures. Some guys get the false sense of security when they have a custom gun/tight chamber and do not see the signs, even when they are running pretty hot. This program sounds interesting and I might get it yet, but I am afraid it is a curiosity only. The warning they give you pretty much tells it all. It might be handy if you have developed a wildcat and have no place to turn to get load data. It would give you a starting point, but I would still be leery and proceed very cautiously.

[Castaway]

beemanbeme, I guess the reason I didn't mention the ways we've been able to skirt the edges of disaster is I made the assumption that  a reliable reloading book was used to develop loads near the top end of performance and the loader used the book data.  Personally, I'd trust the published loads that are actually pressure tested more so than a program that approximates pressures.  The answer to the question, is there's no answer short of actually pressure testing the rounds and that I did say.

[steve4102]

In many cases you'd not even be able to dump that much powder of those types into the case if you use a sledge hammer to pound it in. Much of the data on those sheets that purported to be safe pressures were as much as 10-12 grains more than is safe in a .30-30 case even tho the AI case adds at most 4 grains of extra capacity as measured by me on the same case before and after fire forming.

  OK, lets double check your 30-30 AI loads.  Post them here so we can all see how they compare to others that use QL. 

  Here is an example of what I came up with in the 30-30 vs 30-30AI
  First the 30-30.  Lyman 48 lists this load at 28.5gr of 30-31. 2054fps and 36,900psi.

Cartridge          : .30-30 Win. (SAAMI)
Bullet             : .308, 170, Hornady FP 3060
Cartridge O.A.L. L6: 2.550 inch or 64.77 mm
Barrel Length      : 24.0 inch or 609.6 mm
Powder             : IMR 3031

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

-20.0   80    22.80   1780    1196   21302   3836     89.9    1.825
-18.0   82    23.37   1822    1253   22578   3956     91.1    1.780
-16.0   84    23.94   1864    1312   23931   4072     92.3    1.736
-14.0   86    24.51   1907    1372   25367   4183     93.4    1.693
-12.0   88    25.08   1949    1434   26889   4290     94.4    1.651
-10.0   90    25.65   1991    1496   28512   4392     95.3    1.611
-08.0   92    26.22   2033    1560   30239   4488     96.1    1.572
-06.0   94    26.79   2075    1625   32075   4577     96.9    1.533
-04.0   96    27.36   2116    1690   34027   4661     97.6    1.496
-02.0   98    27.93   2158    1757   36108   4738     98.2    1.460  ! Near Maximum !
+00.0  100    28.50   2199    1825   38325   4808     98.7    1.423  ! Near Maximum !
+02.0  102    29.07   2240    1893   40690   4870     99.1    1.387  ! Near Maximum !
+04.0  104    29.64   2280    1962   43214   4925     99.4    1.352  !DANGEROUS LOAD-DO NOT USE!
+06.0  106    30.21   2320    2032   45910   4972     99.7    1.318  !DANGEROUS LOAD-DO NOT USE!
+08.0  108    30.78   2360    2103   48793   5012     99.9    1.285  !DANGEROUS LOAD-DO NOT USE!
+10.0  110    31.35   2400    2174   51878   5043    100.0    1.254  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba    100    28.50   2305    2005   46674   4606    100.0    1.319  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba    100    28.50   2050    1586   31187   4707     92.3    1.550


  Now the 30-30 AI data.    As you can see to reach the same 36,900 psi the AI round has only 30.5gr of 30-31, not 10-12 gr more as stated above.

Cartridge          : .30-30 Ack Imp
Bullet             : .308, 170, Hornady FP 3060
Cartridge O.A.L. L6: 2.550 inch or 64.77 mm
Barrel Length      : 24.0 inch or 609.6 mm
Powder             : IMR 3031

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

-20.0   75    24.40   1821    1252   20832   4186     91.5    1.838
-18.0   77    25.01   1863    1310   22039   4312     92.6    1.794
-16.0   79    25.62   1905    1370   23318   4434     93.7    1.751
-14.0   81    26.23   1947    1431   24669   4551     94.7    1.710
-12.0   82    26.84   1989    1493   26101   4662     95.6    1.669
-10.0   84    27.45   2030    1556   27622   4768     96.4    1.630
-08.0   86    28.06   2071    1620   29229   4868     97.1    1.592
-06.0   88    28.67   2113    1685   30929   4961     97.7    1.555
-04.0   90    29.28   2153    1750   32734   5048     98.3    1.518
-02.0   92    29.89   2194    1817   34653   5128     98.8    1.483
+00.0   94    30.50   2234    1884   36684   5200     99.2    1.449
+02.0   96    31.11   2274    1952   38839   5265     99.5    1.414
+04.0   97    31.72   2314    2020   41127   5321     99.8    1.380  ! Near Maximum !
+06.0   99    32.33   2353    2089   43559   5370     99.9    1.346  ! Near Maximum !
+08.0  101    32.94   2391    2159   46143   5411    100.0    1.314  !DANGEROUS LOAD-DO NOT USE!
+10.0  103    33.55   2430    2228   48893   5444    100.0    1.283  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba     94    30.50   2336    2059   44756   4970    100.0    1.343  ! Near Maximum !
Data for burning rate decreased by 10% relative to nominal value:
-Ba     94    30.50   2090    1648   29815   5131     93.7    1.573

[Graybeard]

OK, lets double check your 30-30 AI loads.  Post them here so we can all see how they compare to others that use QL. 

You can't be serious! This was six or eight years ago. The load sheets he gave me were clearly bogus and were tossed in the trash years ago. Many of the recommended loads on those print out sheets that clearly stated they were supposed to be safe loads were ten or more grains over the MAXIMUM case capacity and powder would flow out onto the table if you tried to cram that much in.

I'm merely giving one instance the ONLY one I've had with the use of QL load/pressure data and I was not the one who generated them they were provided to me by the person I bought the barrel from.

Anyone or anything that pretends to accurately predict pressures without taking into account the chamber and barrel dimensions, primers/cases used and variations in lots of powder are bordering on the insane.

[AtlLaw]

Thanks to Steve and Tim I have a little better grasp of QL now.  Personally I think it would be a pretty neat little toy to play with, kind of like measuring case heads for hours, but I, like all of you, would take it's... uh, predictions with less then a grain of salt.  However, I can see the possibility of someone from the shallow end of Bee's gene pool starting right out with a charge just below or even at the "Near Maximum" level.

Still, it adds another level to the discussion.  Now, when telling people about our favorite load we can say "bolt lift was easy, the cases just fell out of the chamber, primers were nice and rounded on the edge, case head expansion was only .0002 and the pressure was only 54K PSI!  All of that and I'm still getting 1000 fps over the published velocity for the load!"   

[steve4102]

Anyone or anything that pretends to accurately predict pressures without taking into account the chamber and barrel dimensions, primers/cases used and variations in lots of powder are bordering on the insane.

  QL takes into account barrel and chamber dimensions.  You must take the actual grains of water of a fired case, seating depth,cartridge length and case length.  The actual brand of brass is not needed as you are using actual internal volumes of your brass.   As I have stated before, QL is just another tool.  Like manuals it is not an absolute, it is mearly a guideline.
  Can you tell me which one of your manuals that you follow to the letter takes into account lot to lot variations?  Can you also tell me which manuals takes into account barrel and chamber dimensions?  As far as I know they can't and don't.  They do however all state to "start low and work up looking for signs of pressure". 

[LaOtto222]

Here we go again

[chutesnreloads]

Found part of what I was looking for.It's a strain guage that measures chamber pressure.The Varmint Hunter magazine#47 July 2003.Page 55 is an article and another on page 92.This is the Oehler Model 43 Personal Ballistic Laboratory.This thing is a chronograph that also has strain guages that are mounted to your chamber while firing.Sounds like a fun and useful toy if you can afford it.There's a website given fabriquescientific.com on there it lists several magazine articles it has been featured in.Oddly enough my magazine isn't listed.There's also another more detailed article in a later issue I couldn't find.Some of you are bound to have some of these articles.

[steve4102]

Here we go again

  Yea, sorry.  I apologize, I just can't help myself.
   GB has never used QL and has no idea what it has to offer.  Making comments about QL's inabilities based on a data sheet from a guy he barely new is just plain ludicrous.  This guy may have had QL so screwed up it really was worthless, but GB has no way of knowing that as he has never gotten past that one bad incident  I'm not going to sit back and read the opinions of a man that has NEVER used a product and not make comments of my own.  IMO if you have no first hand knowledge of a product then your opinion is worthless.

[steve4102]

You can't be serious! This was six or eight years ago. The load sheets he gave me were clearly bogus and were tossed in the trash years ago

  Yes, I am serious.   I would like to know what kind of data this guy used to get these outrageous results.  I have been playing with QL for the last hour or so and the only way I can come up with a 10-12 gr overflow is to select powders that are way to slow for caliber.  QL will run the numbers for any powder cartridge combo you wish.  You still have to stay within the proper burn rate for cartridge.   Do you remember what powder/ bullets he may have listed?
 

[AtlLaw]

Hey Steve, I'm sure in the 6 or 8 years since GB got his data sheet there have been revisions of the program.  I should hope so anyway!  If so, I doubt there would be any way you could duplicate the results, even if you had the data.

But, you and Tim have told me enough that I think I will get a copy... soon's I can hide enough money from mama!