[glock20c10mm]

http://www.shootingsoftware.com/ftp/...%2019%2004.pdf

If you didn't take interest in the above article after THOROUGHLY reading it, I suggest you put yourself in the group of those who should never handload/reload above "book max".

If you did take interest in the above article, I expect you'll also be very interested in the following one covering how temperature, powder, and primer, affect pressure.

http://www.shootingsoftware.com/ftp/...%20Factors.pdf

All said, if there is one thing I've noticed around here, it is wrongful assumption regarding loading to safe maximum pressure levels. I'm not saying the high pressure indicators we are all well aware of shouldn't be implemented. What I am saying is, regardless they exist, they do NOT necessarily reflect how close or far you are from actual maximum SAAMI pressure for any given cartridge.

On the other hand, get a Pressure Trace II system like XmmAuto has, and you'll have something to practically bank on. Either way, to ANYONE who has any interest whatsoever in knowing anything about cartridge pressures, I highly suggest you THOROUGHLY read both articles linked above! I'm talking about invaluable information you hardly ever come across.


Good Shooting!

[hypnagogue]

Originally Posted by glock20c10mm

If you didn't take interest in the above article after THOROUGHLY reading it, I suggest you put yourself in the group of those who should never handload/reload above "book max".

From the looks of this article, the author is taking very small measured differences in case expansion from one specific rifle to base those calculations. Every chamber is different. The Legendary Glock Belly Fire Forming Chamber is not a rifle chamber. It is 30 times looser, and allows for dramatically more brass expansion than any rifle barrel I've ever seen. The half-a-thousandth case expansion he bases his calculation on is not applicable to the 15 thousandths measurable in the G29.

I know DoE, and that entire article would need to be recalculated for the Glock chamber and dramatically lower pressures to make it relevant.

Thanks for the link.

[glock20c10mm]

Originally Posted by hypnagogue

From the looks of this article, the author is taking very small measured differences in case expansion from one specific rifle to base those calculations. Every chamber is different. The Legendary Glock Belly Fire Forming Chamber is not a rifle chamber. It is 30 times looser, and allows for dramatically more brass expansion than any rifle barrel I've ever seen. The half-a-thousandth case expansion he bases his calculation on is not applicable to the 15 thousandths measurable in the G29.

I know DoE, and that entire article would need to be recalculated for the Glock chamber and dramatically lower pressures to make it relevant.

Thanks for the link.

You're exactly right! But isn't that just a tad beside the point that you can NOT rely on case head expansion measurements in determining a safe load for any gun, let alone repeatable measurements close to any exacting degree which can be seen measuring the case heads of 10 different loads that are more/less identical to each other?

[_The_Shadow]

Glock20c10mm, Thanks for posting, I had read these sometime back and they do provide some good insite. I have said all along about working blindly, I never liked the bulged and especially smiled conditions I was see in many post over the years. It was also the reason why I also test in a factory Glock barrel to observe results and to allow expansion if it were to occur, as opposed to just using the S&W 1006 factory barrel or the aftermarket Storm Lake in the Glock 29.

The expression "you got to know when to hold them or when to fold them" so it doesn't become a deadmans hand! Be safe!

[hypnagogue]

Originally Posted by glock20c10mm

isn't that just a tad beside the point that you can NOT rely on case head expansion measurements

This statement is not supported by that study.

[glock20c10mm]

Originally Posted by hypnagogue

This statement is not supported by that study.

What makes you think that?

[hypnagogue]

Originally Posted by glock20c10mm

What makes you think that?

Education. Professional experience.

Rewrite the study, except instead of case expansion, study the effect of arbitrarily short copper cylinders in a copper crusher. The results would be the same -- the error would overwhelm the measurement and make it an unreliable measure of pressure. From that should we conclude that copper crushers can't be used for pressure measurement?

Rewrite the study, except instead of case expansion, study the effect of using an arbitrarily large strain gauge. The results would be the same -- the error would overwhelm the measurement and make it an unreliable measure of pressure. From that should we conclude that strain gauges can't be used for pressure measurement?

Rewrite the study, except instead of case expansion, study the effect of using a arbitrarily thin crystal in piezo pressure transducer. And so on and so on...

The author of the study used an arbitrarily tight chamber to prove that case expansion isn't a useful measure of pressure. That's true -- case expansion isn't a useful measure of pressure in an arbitrarily tight chamber. This is why it shouldn't be used to estimate pressure in fully supported barrels. It's not relevant -- we are talking about Glocks, not bolt action rifles.

Thanks, but I've been around this block before. Industrial engineering is something more than a hobby with me.

[hypnagogue]

One last thing, and I'm done -- I recommend measuring case expansion in standard Glock barrels, not case HEAD expansion. The Famous Glock Smile is a case failure and should never be a deliberate target.

Instead, measure the Glock Belly at the top of the web, at the maximum measured diameter of the entire case. From what I can see, that's what most people are doing, based on the measured values submitted. If you see a Glock Smile, repent, for the end is nigh.

I just want to be clear, because you started this thread as "case head expansion" and that is most definitely NOT recommended.

[ModGlock17]

Originally Posted by hypnagogue

Instead, measure the Glock Belly at the top of the web, at the maximum measured diameter of the entire case. From what I can see, that's what most people are doing, based on the measured values submitted. If you see a Glock Smile, repent, for the end is nigh.

I just want to be clear, because you started this thread as "case head expansion" and that is most definitely NOT recommended.

Then what parametric values should we watch for? What are its corresponding values in pressures?

[hypnagogue]

Originally Posted by ModGlock17

Then what parametric values should we watch for? What are its corresponding values in pressures?

Depends on the gun. The Glock 29 and 20 have different chambers. I would not personally push a load past .434 regardless, and this seems to correspond with book loads of 35,000 PSI in my 29. Frankly, I wouldn't push 37,500 in a Glock 29, regardless of "SAAMI Says" -- I think it's too high for that chamber. Watch the brass, not the book. If you see pressure signs, STOP. (I'm astonished I have to say this...)

[glock20c10mm]

Originally Posted by hypnagogue

Education. Professional experience.

I'll generally leave that alone as I have no idea what your education and professional experience are. What I will say is that there are a plethora of instances clearly showing where those with higher educations and professional experiences have been so far off base that it's not worth a second thought. How you could have thoroughly read and understood ALL the information in the statistical study carried out, along with an understanding of the Pressure Trace II system (not to mention any system that measures chamber pressures in the way they're discussed here), and still come to the conclusion you have is very strange to say the least.

Rewrite the study, except instead of case expansion, study the effect of arbitrarily short copper cylinders in a copper crusher. The results would be the same -- the error would overwhelm the measurement and make it an unreliable measure of pressure. From that should we conclude that copper crushers can't be used for pressure measurement?

Rewrite the study, except instead of case expansion, study the effect of using an arbitrarily large strain gauge. The results would be the same -- the error would overwhelm the measurement and make it an unreliable measure of pressure. From that should we conclude that strain gauges can't be used for pressure measurement?

Rewrite the study, except instead of case expansion, study the effect of using a arbitrarily thin crystal in piezo pressure transducer. And so on and so on...

The way in which you could have come up with the above, knowing what you loosely claim to know is beyond me. If all of the above were theories, I would understand. But they are not. They are all proven methods onto themselves in the most basic sense. What is different between them is the accuracy or lack thereof in which they offer relevant data toward chamber pressure for any given setup, with adjustments made as spelled out and necessary. Why you're bringing up how a pressure measurment system may be rewritten doesn't even make sense in the context of what we know as fact.

Substanciated evidence has proven beyond a shadow of a doubt how the current Pressure Trace II strain gage pressure testing system, used properly, will yield a dramatically higher level of accuracy over the Waters Method which relies solely on pressure ring expansion (NOT case head expansion which is even less reliable than pressure ring expansion).

Do you have even the slightest knowledge of the Pressure Trace II?!? Are you aware of what the Pressure Trace II system all takes into account, partly overall, and partly continuing during the duration of a testing event(s) over time? How about I clue you in, as you obviously have no clue.

What the PTII takes into account for changes that occure throughout a session of testing and therefore adjusts to on its own:

1) Calibration to the current static flow through the gage. (This step repeats after each shot so heating and expansion of the barrel does not affect pressure readings.)

2) Strain gage voltage. (Displays the strain gage voltage applied to the Wheatstone bridge circuit. This will vary from unit to unit but should fall between 4.800 and 5.200 volts. If this value starts to read lower, the batteries may need to be replaced. The program constantly monitors the voltage, and if it is less than 4.8 volts, will disable the module.)


What the PTII takes into account that generally stays the same thoughout a testing session and/or can be adjusted as needed throughout a testing session:

1) The gage factor of the specific strain gage being used. As a side note; you called "it" a strain gauge. This is incorrect. For someone with such an understanding of what's being discussed here it's a tad strange you would have made that mistake. Sometimes gauge and gage are uses interchangeably, but gauge is not reported correct for this application. A gauge is a tool used to measure something, and gage is an actual measure. Output from a strain gage is a recognized measure (microstrains), and probably why this spelling is used by the manufacturer and most engineers. And, in case you care, all strain gages are provided through Vishay Micromesurements for the PTII.

2) What specific barrel you are using.

3) Barrel OD

4) Chamber ID

5) Case Wall Thickness (must use brass that has been fired at least one time)

6) Gage Manufacturer

7) Gage Type and Weight

8) Bullet Diameter

9) Overall Barrel Length

10) Cartridge Case Length

11) Trigger Level (sensitivity) (While waiting for a shot, the module constantly checks current through the strain gage looking for a sharp increase in resistance. The amount resistance must increase before it determines an actual shot is in process is set by the Trigger Level.)

12) Setting the PTII to High Resolution (limits pressure readings to 20,000 PSI, mainly for black powder rifles and shotguns) or Low Resolution (reads to 80,000 psi)

13) Setting the Time Range Options of either: 1.5 Milliseconds (most rifles and shotguns), 2.0 Milliseconds (large bore heavy rifle calibers), or, 3.0 Milliseconds (black powder rifles and muzzle loaders)

14) Pressure Correction Factor


What must be done correctly by the user:

1) Mount the strain gage correctly over the chamber in the barrel.

2) Using the proper adhesive to mount the strain gage.


There are plenty of other values you can add, but not that are used for the unit to calculate anything, unless you want it to display OBT (Optimum Barrel Timing).


Can the PTII be calibrated? YES

What does the PTII all keep track of for you:

1) Peak PSI

2) Area Under the Curve

3) Rise Time (in microseconds)

4) Efficiency (calculated to help indicate the most efficient load in a string)

5) Average peak pressure, area, and rise time.

6) 95% Probability (A distribution function indicating a 95% probability that results will be +/- the indicated value. This is a more accurate number than SD for small samples because it is weighted for the number of samples in the string. When you hide one trace in a group of five the 95% probability number will increase.)

7) Highest Value in the Group

8) Lowest Value in the Group

9) Extreme Spread

10) And much much more.


So Mr. Educated/Experienced-Professional, please explain to the rest of us how the PTII system would create errors that would overwhelm the measurement and make it an unreliable measure of pressure, in conjunction with how using a recalculation for the Glock chamber and dramatically lowering pressures would make accuracy of pressure measurments any more or less relevant in using the Waters Method. I can't wait!!!

Are you literally of the belief that somehow the Waters Method becomes more refined in terms of the measurements it offers toward pressure values/ranges when recalculating for a Glock chamber and dramatically lowering pressures, to the extent you will gain greater refinement of measurements? Please share with us exactly what information has demonstrated how a loose stock glock chamber or loose arbitrary chamber will somehow increase the accuracy level of the Waters Method, as compared to a tight(er) chamber?

The author of the study used an arbitrarily tight chamber to prove that case expansion isn't a useful measure of pressure. That's true -- case expansion isn't a useful measure of pressure in an arbitrarily tight chamber. This is why it shouldn't be used to estimate pressure in fully supported barrels. It's not relevant -- we are talking about Glocks, not bolt action rifles.

Really?!? Again, and you're now going to share with us exactly what information has demonstrated how a loose stock glock chamber or loose arbitrary chamber will somehow increase the accuracy level of the Waters Method, as compared to a tight(er) chamber?????????????? Hey, good luck with that!

Thanks, but I've been around this block before. Industrial engineering is something more than a hobby with me.

I would surmise you have barely set foot on the sidewalk yet. You know what you should do? Ask for the money back for that education you think you received! Doesn't sound like your professional experience it doing much for you either. Or maybe you should simply stop making assumptions on things you aren't schooled in. Hey, you didn't really think the PTII system solely relied on the expansion and contraction of a strain gage on its own, did you?

[glock20c10mm]

Originally Posted by hypnagogue

I just want to be clear, because you started this thread as "case head expansion" and that is most definitely NOT recommended.

AFTER I mentioned the Waters Method, I purposefully put "case head expansion" in quotes because it and the Waters Method are two different things which anyone could learn after reading the link I posted. A number of folks around here are using the terminology "case head expansion" which they don't realize isn't by definition what they mean at all.

[glock20c10mm]

Originally Posted by hypnagogue

Depends on the gun. The Glock 29 and 20 have different chambers. I would not personally push a load past .434 regardless, and this seems to correspond with book loads of 35,000 PSI in my 29. Frankly, I wouldn't push 37,500 in a Glock 29, regardless of "SAAMI Says" -- I think it's too high for that chamber. Watch the brass, not the book. If you see pressure signs, STOP. (I'm astonished I have to say this...)

You should be aware that different brands of brass cases can be of different hardnesses, which throws your ".434 inch" measurement right out the window unless in a discussion with others ALL using the same brand of brass, and preferably from the same lot that have all had either no firings through them yet, or the same amount of firings through them.

[hypnagogue]

Originally Posted by glock20c10mm

The way in which you could have come up with the above, knowing what you loosely claim to know is beyond me.

What are you talking about? No one has questioned the accuracy of the strain gauge system you are talking about. Far from it.



Outdoor Hub mobile, the outdoor information engine

[21Carrier]

Glock20c, here's how my tests went today. I'm posting this here because it was in response to you, and I didn't want to hijack Hubcap500's thread. BTW, I think the Water's Method IN PISTOLS, especially loose Glock chambers that allow for lots of expansion, is a VERY good way to gauge pressure. I am nearing 9,000 rounds reloaded in 10mm, many of which have been off the charts. I still have not had a case head rupture, and I still have not had but 11 Glocksmiles (got a TINY one today in a nickel case). I 100% attribute my safe reloading to the Water's Method. It's easy to question it when you don't see it in person, but I can watch it happen before my eyes. I saw it today. When doing the 135gr Nosler/Longshot workup today, the case expansion got greater and greater until I ran out of loads to shoot. I was nearing my max, so I would have stopped anyway.

Glock20c, it sounds like you doubt the Water's Method, but I think it is VERY valid. I see it's results ever time I shoot, and I REALLY think you should reconsider. I KNOW it is an estimation, but it works. If not, I would have blown my gun up by now. I will list the case expansion figures I got to compare 800-X vs. Longshot. At least in my G29, 800-X gets better velocities. Here is what I consider proof of that in 135gr, 155gr, and 200gr bullets.

I am not going to post all of the velocities in the interest of time and space, but let me know if you want to see them for a load.

Weather: 95*F, 51% humidity, 495ft ASL

Chronograph: CE Prochrono Digital at 10ft.

Load Data: all loads used Starline nickel brass (yellow for 135gr Noslers), CCI 300s, and a COAL 1.260"

155gr Gold Dot/11.2gr 800-X:
10 rounds
High: 1390
Low: 1337
Average: 1364
ES: 53
SD: 19
Max Exp. = .4335"

155gr Gold Dot/11.5gr 800-X
10 rounds
High: 1412
Low: 1333
Average: 1388
ES: 79
SD: 23
Max exp. = .4340"

155gr Gold Dot/11.8gr 800-X CAUTION - ABSOLUTE MAX LOAD!!!
10 rounds
High: 1460
Low: 1375
Average: 1409
ES: 85
SD: 34
Max exp. = .4340" (one Glocksmile at .4345")

155gr Gold Dot/10.0gr Power Pistol:
10 rounds
High: 1267
Low: 1206
Average: 1236
ES: 61
SD: 21
Max exp. = .4335"

155gr Gold Dot/13.0gr Blue Dot:
10 rounds
High: 1287
Low: 1238
Average: 1257
ES: 49
SD: 17
Max exp. = .4335"

155gr Gold Dot/11.5gr Longshot:
10 rounds
High: 1373
Low: 1254
Average: 1290
ES: 119
SD: 36
Max exp. = .4340"

Here is the first example. 11.2gr 800-X got .4335" expansion, and hit 1364fps. 11.5gr 800-X showed .4340", and hit 1388fps. 11.8gr showed .4340", and hit 1409fps. Using 11.5gr as a reference, 800-X made 98fps more with the same case expansion. Using 11.2gr as a reference, 800-X made 74fps more.

200gr XTP/8.0gr Longshot:
10 rounds
High: 1036
Low: 978
Average: 1008
ES: 58
SD: 18
Max exp. = Not recorded since I went much higher

200gr XTP/8.3gr Longshot:
10 rounds
High: 1068
Low: 992
Average: 1037
ES: 76
SD: 21
Max exp. = .4335"

200gr XTP/8.5gr Longshot:
10 rounds
High: 1084 (2 at this velocity)
Low: 983
Average: 1052
ES: 101
SD: 32
Max exp. = .4335"

Comparing this load to 800-X, 800-X got 1114fps with 8.7gr, and 1124fps with 9.0gr. Both of those loads showed .4335" expansion, same as 8.5gr Longshot. So, same expansion, nearly 75fps more.

135gr Nosler JHP/12.1gr Longshot:
10 rounds
High: 1433
Low: 1341
Average: 1373
ES: 92
SD: 27
Max exp. = Not recorded, only higher charges

135gr Nosler JHP/12.3gr Longshot:
10 rounds
High: 1441
Low: 1341
Average: 1372
ES: 100
SD: 27
Max exp. = Not recorded, only higher charges

135gr Nosler JHP/12.5gr Longshot:
10 rounds
High: 1457
Low: 1328
Average: 1382
ES: 129
SD: 38
Max exp. = .4340"

135gr Nosler JHP/12.7gr Longshot:
10 rounds
High: 1430
Low: 1312
Average: 1365
ES: 118
SD: 39
Max exp. = .4340"

Again, here I get the same .4340" expansion with anywhere from 1515fps to 1551fps with 13.0gr 800-X. So, using the best Longshot charge (12.5gr), I gained AT LEAST 133fps by switching to 800-X.

[21Carrier]

I started to read the article, then I realized, I KNOW the Water's Method and pressure ring measurement is flawed, but REALLY what else am I going to do?! Guess? Pray for the best? Just HOPE I don't blow myself up? Yeah, I'll keep doing it. It's kept me safe so far. If nothing else, just slowly working up and watching for Glocksmiles works.

The bottom line is NO ONE thinks it's absolute. We realize that. But we have nothing else to use, so it's the best thing we can do. So I'll keep doing it, and I have a feeling I'll stay safe.

[hypnagogue]

Originally Posted by glock20c10mm

You should be aware that different brands of brass cases can be of different hardnesses, which throws your ".434 inch" measurement right out the window

It does no such thing. In a Glock chamber, the maximum case expansion will be .4345, regardless of brass. That's the limit, due to the chamber dimensions. Beyond that and you are flying blind, and the next stop is case failure.

That will not correspond to the same pressure in all brass, but it will correspond to the absolute max for that brass before Glocksmile.
Regardless, at .434, STOP. That's my limit.

[21Carrier]

Originally Posted by hypnagogue

It does no such thing. In a Glock chamber, the maximum case expansion will be .4345, regardless of brass. That's the limit, due to the chamber dimensions. Beyond that and you are flying blind, and the next stop is case failure.

That will not correspond to the same pressure in all brass, but it will correspond to the absolute max for that brass before Glocksmile.
Regardless, at .434, STOP. That's my limit.

I agree 100%. I start getting Glocksmiles right at .4345"-.4350". I never go past .4345". If I see .4340", I know it's time to cool it. Like you said earlier, Glocksmiles mean you are damaging cases, and the next round could cause a failure.

I think the problem with the above article is the same problem with using a fully supported aftermarket barrel to work up loads, and this is an issue I've noted before. If you only get .425" expansion with a max load, you can't see the difference between heavy and light loads. A light load in my gun will expand brass to .431-.432". If I were using an aftermarket barrel, it would be .425". However, I would get the same measurement with a nuclear load. With it, I'd still see .425". However, with my Glock barrel, I'd see .434", and I'd know I'm pushing it.

To me, this study is the same. The chamber is too tight to allow for any DIFFERENCES in brass expansion to be seen. Because it's so tight, there's not room for the brass to expand. I just don't think one study which is using a different type of cartridge, in a totally different type of weapon is totally applicable.

All of that being said, I totally agree with Glock20c that we cannot reliably get pressure numbers by measuring brass expansion. However, I think we CAN get RELATIVE pressure measurements. I DO think I can say load X has a higher pressure than load Y, because load X showed more case expansion. Of course there will be small brass flaws and variances that can cause variations, but that's why I measure at least 10 cases of a load and use the average measurement. It helps eliminate one weak or one strong case from skewing the measurements.

[robert91922]

Originally Posted by 21Carrier

I agree 100%. I start getting Glocksmiles right at .4345"-.4350". I never go past .4345". If I see .4340", I know it's time to cool it. Like you said earlier, Glocksmiles mean you are damaging cases, and the next round could cause a failure.

I think the problem with the above article is the same problem with using a fully supported aftermarket barrel to work up loads, and this is an issue I've noted before. If you only get .425" expansion with a max load, you can't see the difference between heavy and light loads. A light load in my gun will expand brass to .431-.432". If I were using an aftermarket barrel, it would be .425". However, I would get the same measurement with a nuclear load. With it, I'd still see .425". However, with my Glock barrel, I'd see .434", and I'd know I'm pushing it.

To me, this study is the same. The chamber is too tight to allow for any DIFFERENCES in brass expansion to be seen. Because it's so tight, there's not room for the brass to expand. I just don't think one study which is using a different type of cartridge, in a totally different type of weapon is totally applicable.

All of that being said, I totally agree with Glock20c that we cannot reliably get pressure numbers by measuring brass expansion. However, I think we CAN get RELATIVE pressure measurements. I DO think I can say load X has a higher pressure than load Y, because load X showed more case expansion. Of course there will be small brass flaws and variances that can cause variations, but that's why I measure at least 10 cases of a load and use the average measurement. It helps eliminate one weak or one strong case from skewing the measurements.

Agree with you about full supported aftermarket barrels and max. expansion. In my IGB barrel there's always .431 case expansion (if I recall correctly) no matter if it's 1330/180, 1250/180, 1250/200, 1400/165 or 1200/185gr load. I can only watch flattening of primers. When they are flat enough it's hot enough. If some of them fall out it's way too much - time to step down 0.4gr at least.
Such case gets expanded primer pocket as well and becomes useless for further reloading....perhaps a drop of blue glue would fix that but not worth to risk. In EU I pay way more for 10mm brass than you in US but wouldn't do that anyway.

[glock20c10mm]

Originally Posted by 21Carrier

I started to read the article, then I realized, I KNOW the Water's Method and pressure ring measurement is flawed, but REALLY what else am I going to do?! Guess? Pray for the best? Just HOPE I don't blow myself up? Yeah, I'll keep doing it. It's kept me safe so far. If nothing else, just slowly working up and watching for Glocksmiles works.

The bottom line is NO ONE thinks it's absolute. We realize that. But we have nothing else to use, so it's the best thing we can do. So I'll keep doing it, and I have a feeling I'll stay safe.

Originally Posted by 21Carrier

All of that being said, I totally agree with Glock20c that we cannot reliably get pressure numbers by measuring brass expansion. However, I think we CAN get RELATIVE pressure measurements. I DO think I can say load X has a higher pressure than load Y, because load X showed more case expansion. Of course there will be small brass flaws and variances that can cause variations, but that's why I measure at least 10 cases of a load and use the average measurement. It helps eliminate one weak or one strong case from skewing the measurements.

I'm down with that. IMO the main thing is to realize the chance one might be taking. There's been a lot of talk here regarding the Waters Method lately, and the more I read the easier it was starting to sound. The point is, this is an open forum, and just as some shouldn't be trusted with a scissors (even when standing still), there are also probably some who shouldn't be trusted micrometering 10mm brass as they attempt nuclear loads. So for those that are thinking about giving the Water's method a try for the first time, it isn't hard to do, but care should be taken to do it VERY carefully, while still keeping in mind it is only a poor man's way of measuring pressure, where you never really get a measurement in PSI. It's not about me suggesting nobody should be doing it. It's about me telling people to err on the side of caution if you will, while realizing the Waters Method is not foolproof, and without guarantees.

Just as was said in the article, and as 21Carrier has reemphasized, when using the Waters Method, it is probably a very smart thing to be taking the average pressure ring measurement from a minimum of 10 same loads and then averaging in the hope of a highest safety level. But once one out of the "ten" banana-peels your stock Glock barrel, remember, if the brass stayed in one piece, you can still get a honest measurement.

[Taterhead]

Originally Posted by ModGlock17

Then what parametric values should we watch for? What are its corresponding values in pressures?

The point to the Waters Method is that we handloaders do not know what the pressures are. Finding a factory load known to be at or near max pressure will give a benchmark upper limit. Buffalo Bore in Starline Brass expands to right near 0.434" in my Glock 20. BB is obviously getting up there in terms of pressure. Needless to say, if BB were to push pressures higher, brass would start to smile and then eventually worse.

Not coincidentally, some of the known hot factory published data expands my brass to, you guessed it, close to 0.434". Starting loads are around 0.431". My range ammo is consistently about 0.4325". It is an observable progression from starting load to max.

For developing loads where data does not exist, understanding the expansion characteristics of published data is useful. Hot = 0.434".

Developing several dozen bullet/powder/primer combos over the years has revealed predictable case expansion. I would disagree with the OP that it is a useless data point.

Also it IS true that a fully supported chamber will not reveal as much about pressure as will a loose Glock chamber. The fully supported chamber will not let the case expand beyond a certain point thus a warm load will have similar pressure ring measurements as do hot.

Final note. Different brass expands at different rates. Generally you will find nickel cases expand less for a given pressure in a Glock barrel than does brass. That is why I only use Starline brass. Predictable known results.

[WorrGlock]

I have had two case head seperations both were 40 S&W and both happened about 12 years ago.

1. Glock 23 shooting federal hydro shock, factory loaded.
2. Beretta 96D shooting remington yellow box FMJ, factory loaded


My time with .40 was very short lived both of these happened within a year, I went back to shooting 9mm and have not had any problems since.

[MinervaDoe]

Originally Posted by glock20c10mm

On the other hand, get a Pressure Trace II system like XmmAuto has, and you'll have something to practically bank on.

Interesting stuff. Thanks for posting it.
http://shootingsoftware.com/pressure.htm
So, I understand how you would hook this up to a bolt action rifle, or a Thompson Contendor, but am I correct in assuming that this won't work on an automatic pistol?

Still, this is really impressive stuff that an amateur (like me) can use.

As steel around the barrel expands the gage is stretched and current flow through the grid is altered.

http://www.shootingsoftware.com/mm5/...tegory_Code=PT

[blastfact]

I'm all for measuring, looking at primers and such to see if the pressures are about to get out of hand.

But I don't for the life of me see the Glock smile as anything reliable as a sign of over pressure. I've seen folks buy OEM 9, .40, 45 acp right off the rack and leave junked Glock brass at the range.

[Kegs]

I haven't read this yet, but I'm gonna. I'm saying thanks for posting it ahead before I read it...'cause I am interested.