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Old 02-07-2013, 12:42   #51
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Quote:
Originally Posted by _The_Shadow View Post
It might be, but I don't wish to work to those levels in the 40S&W cartridges...


Did the Quickload program ever get data for the IMR800X powder? ??? LongShot is very simular by weight as 800X.
* I agree to hot .
* No the QL program does not have IMR 800 X in it yet.

Sean

Last edited by 475-480; 02-07-2013 at 12:43..
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Old 02-07-2013, 13:02   #52
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OP....very glad you are OK. Scary I'm sure.

I honestly don't get loading hot 40. Wasn't the 40 originally developed because..... well because it isn't 10mm?

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Old 02-07-2013, 14:46   #53
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First, thanks to Shadow for pulling all those rounds. I could not believe my ears when he called me and told me that he found 10 grains of longshot in a round. I am not a reloader, but even I know that was just crazy.

Hindsight is 20/20, and I'm just glad I got all my eyes and fingers to consider it. Looking back, I trusted Mike to load a safe but hot round for my xdm. I now believe that trust was wrongfully placed. I looked at the kaboom stories from a couple of years ago....very similar to what happened to me. Shortly after Mike made my ammo, he decided to "back off" a little and began to reduce some of his loads. Surely he had to know he was doing some crazy, dangerous stuff. Me, I was naive, and wanted to believe that I could shoot this jacked up stuff without fear.

We learn, and we move on, hopefully sharing what we've learned along the way. It cannot be overstated, Swamp Fox ammo is dangerous. We have no way of knowing his quality control on any given batch, or what he was thinking on any given day. I think it has been stated somewhere in this thread that Mike tended to vacillate with his thinking and his actions. A dangerous way to make ammo.
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Old 02-07-2013, 15:12   #54
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It seems making your own ammo is the way to go. As long as you don't get distracted while reloading or ingest something sinful before hand, you would (or should) know what you get.
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Old 02-07-2013, 18:07   #55
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So it looks like he was shooting for 9.6g, and everything else was just the deviations due to extremely poor process control. Not a matter of +/- .2g, which would have been poor anyway, but -.2/+.4, which is garbage. So much for "true 10mm ballistics".
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Old 02-07-2013, 18:19   #56
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Originally Posted by broncobuddha1 View Post
OP....very glad you are OK. Scary I'm sure.

I honestly don't get loading hot 40. Wasn't the 40 originally developed because..... well because it isn't 10mm?
You're correct, that was why the 40S&W came into being. Which makes me wonder why some people buy the 40 and then extra hot loads so it'll be closer the 10 instead of just buying the 10 to start with.
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Old 02-07-2013, 22:18   #57
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You're correct, that was why the 40S&W came into being. Which makes me wonder why some people buy the 40 and then extra hot loads so it'll be closer the 10 instead of just buying the 10 to start with.
Because the 10 has vicious recoil. Haven't you heard?
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Old 02-08-2013, 08:07   #58
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My purpose for the 40S&W is for building proficiency and maintaining trigger time mostly with cast bullets. Using the conversion barrels yields the same sight picture and trigger/grip feel.

The conversion barrels allow me to also used other cartridges...Handloaders are just like that, if the find brass they want to loaded it up and shoot it!
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Old 02-08-2013, 09:18   #59
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Originally Posted by oldman11 View Post
You're correct, that was why the 40S&W came into being. Which makes me wonder why some people buy the 40 and then extra hot loads so it'll be closer the 10 instead of just buying the 10 to start with.
I can't speak for everyone, but I loaded for the 10mm for years. I guess the very same could be said for 10mm guys who load the 10mm trying make it a .41 Magnum. Why not buy a .41 Mag to start with? Someone can't load for the .40 to get the most out of it, but can load the 10mm well beyond book and that's okay?

All I'm saying is, you can load the 10mm warm and you can load the .40 warm. Same precautions apply to both, there is not an extra margin of safety because it's a 10mm instead of a .40 because the 10mm case isn't any stronger than the .40 case, if anything the opposite is true. Loading warm/hot for the 10mm is common, why would it be any different for the .40?
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Old 02-08-2013, 09:57   #60
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SDGlock23, As is with every cartridge ever developed, there are those that will push till something gives! How much is too much?...OUCH! They are looking for maximum performace throwing caution to the wind.

One thing that comes to mind in the Op's situation, pressure testing if it is done is done so in a fixed barrel fixture. While things may have been within certain limits during that testing, the dymaics of the semiauto pistols can change the way things happen thru out the pressure and ejection phases. Think of bolt action rifle vs. blowback semiautos...

Early unlocking of the barrel and slide, can actually be a cause of case failures, as the early ejection cycle is dragging the cartridge out of the chamber under pressure, increasing unsupported areas. The case expansion could actually work to further increase unsupported conditions pushing itself out of the chamber.

Primers being popped out, can move the slide back from the locked possition, the case maybe forced off the extractor hook, to be left in the chamber.

The question of the aftermarket barrel itself raises some concerns, the angles of the locking lug on the barrel in relation to the angles of the locking block in the frame, could have been different form that of stock arrangements. There is some data to support this on the various Glock gun sales sites, suggesting poor fitting and lock-up situations.

These are a few things that come to mind with the dynamics involved for the Glock and other guns.

The reason I took on this Pull-Down process, was two fold for me, I like to study what lead up to the situation and also to provide better insite, so everyone could learn something from Deadandgone's mishap with his Glock 29. After all it was his intent to post his information for these reasons of having others learn something as well.
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Old 02-08-2013, 12:42   #61
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Excellent post, Shadow, as usual.
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Old 02-08-2013, 19:06   #62
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Your post is ok, but this part...
Quote:
Originally Posted by _The_Shadow View Post
While things may have been within certain limits during that testing, the dymaics of the semiauto pistols can change the way things happen thru out the pressure and ejection phases. Think of bolt action rifle vs. blowback semiautos...

Early unlocking of the barrel and slide, can actually be a cause of case failures, as the early ejection cycle is dragging the cartridge out of the chamber under pressure, increasing unsupported areas. The case expansion could actually work to further increase unsupported conditions pushing itself out of the chamber.
is totally wrong. Nothing is dragging the cartridge out under pressure, and it cannot push itself out. There is something like 5 tons of force needed to pull the case out of the chamber during firing, and less than 1 available to push it to the rear.

The things that caused a problem was a manufacturer ignorant of simple physics creating cartridges that were far over safe limits, and loading them uing a faulty process with non-existent quality control.

Last edited by Any Cal.; 02-08-2013 at 19:07..
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Old 02-08-2013, 20:57   #63
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I agree that they these cartridges were over loaded...Yes at the peak of pressure the casing stretches to fit the chamber...but
Once the case has started to tear due to excessive forces, and as it stretches to fill voids, the moving metal can work to force itself further out of the chamber like a pry bar or lever. This can be seen by placing cartridges back in the chamber for measuring purposes, in this insident we don't have the brass to see. Some smiled brass have shown more stretch than the original support of the fully chambered round. The blow back action is dynamic and extreme forces change those dynamics...but think about the entire event, not just the highest pressure peak phase. Even as pressure is dropping off some work can still be done before the complete drop off.

Another part of the equation is the emense amount of heat produced, this changes the properties of the brass as it absorbs this energy, the chamber walls act to absorb some of the heat from the brass, but the unsupported areas don't have that advantage. The amount of heat sink is not there, so it is subject to the high heat stress in addition to the high pressure. This combination is probably why we see the blown out brass at the feed ramp area...

I do ask myself what if different brass was used? Would this have still happened?
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Old 02-09-2013, 02:44   #64
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The point of saami specs is to keep questions like that from arising. If you are working in the limits there won't be a problem. The gun, brass, primers, etc. will handle it. If you run outside the specs you are just guessing as to which part will break first.

With hot rod cars you beef up each part that breaks, and over time the entire system becomes stronger. With reloading, you should be adhering to a spec to insure that parts do not break, as results can be catastrophic.

I still don't see the possibility of the early unlock you worry about, but will concede that I was almost wrong once, as evidenced earlier in this thread...

Last edited by Any Cal.; 02-09-2013 at 02:45..
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Old 02-09-2013, 15:36   #65
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Sorry Any Cal. Shadow is right in his thinking.

Many auto pistols unlock early. Is it enough to cause a kaboom? No. And one does not need over spec ammo to see it. Every time I go to my range I can always find brass thats been shot from a semi auto pistol that has unlocked a tad early.
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Old 02-09-2013, 17:56   #66
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I can't speak for everyone, but I loaded for the 10mm for years. I guess the very same could be said for 10mm guys who load the 10mm trying make it a .41 Magnum. Why not buy a .41 Mag to start with?
Because Glock doesn't make a .41 Magnum. I Can't find a 1911 in .41 Magnum either.
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Old 02-09-2013, 20:31   #67
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You know this is just not a Glock problem! Here is a story of a S&W Shield KB using Cor Bon Glaser Ammo.
http://smith-wessonforum.com/smith-w...went-boom.html

or

http://ingunowners.com/forums/handgu...sad_story.html
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Old 02-10-2013, 06:30   #68
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Shadow, the highest recoil spring is 24lbs for G20 and 23lbs for G29. Are they the best remedy for early release ? I think of the problem as expansion outside of the chamber, so if we keep it in chamber longer then it'd be ok.

I wonder what we CAN do, if it is inherent to the design of some hand guns.


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Old 02-10-2013, 07:33   #69
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I think those if us who handload hot realize there is too much varianceIn those charge levels. Swampfox made some serious ammo, but...


Quote:
Originally Posted by _The_Shadow View Post
Deadandgones Swamp Fox ammo arrived today. HERE is what was inside!

Cartridgeis from Ammo Manufacture: SwampFox Ammo 165gr GDHP
BallisticsInformation: 40S&W (Too HOT)
Advertized MuzzleVelocity: 1325 fps
Advertized MuzzleEnergy: 643 ft. lbs
BrassMake/Headstamp: Star Line – Brass
BulletMake/Weight/Construction/Info;Length 0.5780”/Dia.0.400”: Speer Gold Dot 165 gr.JHP actual weight 165.6 grains (heavy crimp bullet ring 0.3900”)
C.O.A.L.:1.1225”
Primer:Nickel color
Case:Diameter 0.4215” Crimp Diameter 0.4220” Length 0.8445”
PowderDescription/Positive ID/Type/Charge Weight: LongShot 10.0 grains
***(2.2 gr over Hodgdon's listed data)
Pictures: Before/After disassembly:
The 10 Ring


The 10 Ring
The 10 Ring

The 10 Ring

The 10 Ring

In my non-professional opinion I feel that Swamp Fox pushed this loading too far. 2.2 grains in this smaller 40S&W casing. This led to extreme over pressures which resulted in the brass casing's failure. The over pressure of expanding hot gas blew the casing head out, which bled this high pressure jet of gas down into the magazine well. The frame was compromised before the magazine was ejected. Without having seen or observed the damaged gun or the damaged cartridges or other cartridges ion person, I might speculate that, it was possible the gas was forced into the next cartridge at the top of the magazine, which may have ignited that charge of powder as well, to further add to the damage experienced.

This was a tragic event so, I wish to thank Deadandgone for sharing his experiences with us here on GlockTalk and wish him a speedy recovery.

Those of you who have some of SwamFox's ammo, you may want to get with someone who is a handloader to get a better understanding of what you have for safety sake!
Mike Willard is no longer with us (R.I.P.) to make things right.

add data 02/07/2013
Here is the run down of all 35 SwampFox Ammo 40S&W cartridges loaded with Hodgdon's LongShot powder, as pulled-down from Deadandgone box. Once again we wish to thank him for sharing so we can learn for this incident!

13 cartridges @ 09.6 gr / 11 cartridges @ 09.4 gr / 4 cartridges @ 09.8 gr / 4 cartridges @ 09.9 gr and 2 cartridges @ 10.0 gr

10.0 gr
09.9 gr
09.6 gr
09.4 gr
09.6 gr
09.6 gr
10.0 gr
09.6 gr
09.4 gr
09.9 gr
09.8 gr
09.8 gr
09.6 gr
09.8 gr
09.6 gr
09.8 gr
09.6 gr
09.6 gr
09.4 gr
09.6 gr
09.4 gr
09.4 gr
09.4 gr
09.6 gr
09.4 gr
09.4 gr
09.9 gr
09.8 gr
09.9 gr
09.4 gr
09.6 gr
09.6 gr
09.4 gr
09.6 gr

All loads were checked on two scales, the loads at 09.9 grains were for my balance beam RCBS 5-10 Scale these would have shown 09.8 on the digital because it only shows even numbers in the tenths column...
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Old 02-10-2013, 07:53   #70
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We can all speculate some here, based on everyone's experiences, however I am not trying to flame anyone and I do read everyone's expressed views and take them in as part of my study...as a reminder this is 40S&W SwampFox Ammo loaded HOT (too hot) in an aftermarket barrel on a Glock 29, extra power RSA and some other things.

Things that do also come to mind...
Read at CCR raceframes...http://www.ccfraceframes.com/faq-barrels.html

Locking blocks, back a while Carrier had his break. While he was testing some hot loads, did the barrel (aftermarket IIRC) have angles of the lock lug different that led to the locing block breaking? Not known...

Deadandgone started experiencing some issues prior to the KB, did the locking block fail? Did that lead to out-of-battery situation? Early Unlock? Don't know...
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Old 02-10-2013, 09:24   #71
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unable to find brass

Went to find brass in the woods where the explosion occurred. When I say woods, a heavily wooded area near my home. Took the wife with me, and we both searched for the casings...unable to find anything. No metal detector, just two sets of eyes...no luck.

Shadow, the instances of "unusual bullet behavior" occured with my xdm 40 cal. Prior to the explosion in the g29, there were no tip offs or clues as to what was about to happen as I was shooting the Glock. Again, a really bad misconception on my part...I knew the ammo was behaving oddly, but I felt safe shooting it in my g29 allmighty. It is simply luck that it didn't blow up the xdm.

I don't want to speculate what would have happened if the xdm had blown up. I am just glad that Glock makes a sturdy gun...and that the main force of the kaboom seemed to go down as opposed to backwards.

I have no brass to back up my thinking....I wish I did, it would tend to solve the mystery part of the explosion. However, given the measurements provided by Shadow, I feel confident that the ammo failed, was too hot, and created the explosion. Had I not been so naive in my thinking, this thread would not exist, so I cannot eliminate my part of this equation.

We can substitute the word ignorant for naive...both words fit just fine. I didn't know any better....my thinking was flawed.

Now, I know. If I were to load ammo that crossed the line between safety and hot ammo....I'd be in business selling Swamp Fox ammo.

Sorry, it kind of hurt to say that, and I will never sell any of my remaining stash of 10 mm Swamp Fox ammo. I won't shoot it, but I won't sell it. Especially the stuff marked "supported barrel only".I know the difference between right and wrong...the line is not blurry for me. And Mike, if you were still alive, I would tell you that....face to face.

And, as Forrest Gump might say, "And thats all I have to say about that."
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Old 02-10-2013, 10:54   #72
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Originally Posted by _The_Shadow View Post
Locking blocks, back a while Carrier had his break. While he was testing some hot loads, did the barrel (aftermarket IIRC) have angles of the lock lug different that led to the locing block breaking? Not known...

Deadandgone started experiencing some issues prior to the KB, did the locking block fail? Did that lead to out-of-battery situation? Early Unlock? Don't know...
Shadow, I think that is absolutely a possibility. I would think that a locking block would break while the barrel was smacking it traveling back towards the shooter in recoil. If that is the case, then the broken locking block would allow the barrel+slide to remain locked longer than necessary. This would cause the normal locked dwell time to increase, not decrease, so that would actually make a KB less likely on that round. On the next round, if it chambered for firing, the barrel+slide might not be fully locked in the normal forward position, reducing the travel of the locked slide+barrel. For a typical handloaded hot 180 XTP at 1200fps, if the normal unlocking travel were reduced from .210" to .070", that would most definitely cause a KB! See explanation below....

Physics: It's not just a good idea, it's the law!

OK, I've been wanting to do this for some time now, but never sat down and took the time to do it. But what I've done is to create a spreadsheet to do some calculations on barrel-slide lock time, pressure, slide velocity, etc. Based on a realistic velocity for firing a 180XTP from a G29, and some assumptions that I've made below, I've checked my numbers a couple of different ways, and I'm 99% sure they're OK. It took a while to figure out how to work the math using the English (pounds, feet, etc.) system. The SI system (MKS) is so much simpler!

Assumptions:
- Glock 29
- Barrel weight (weighed) 4.0 Oz. (0.25lb)
- Slide weight (weighed) 15.6 Oz. (0.975lb)
- Slide + barrel (locked) 19.6 oz. (1.225 lbs)
- 180gr. XTP fired at 1200fps plus 10gr. of powder(hot, don't try this without working up)
- Slide travel before barrel unlocks from slide (measured) 0.210"
- Spring force 17lbs
- Linear acceleration ***
- Distance bullet traverses barrel 3.145" (measured from where a 180 XTP would be positioned in the 3.77" barrel in chamber when shot is fired)
- Conservation of momentum, M1*V1 = M2*V2, where "1" is bullet and "2" is barrel + slide
- Neglecting slide friction and small amount of momentum transferred to the shooter in the first 500 us of shot initiation (time it takes to get the bullet out the bore).
- Neglecting force of "jet effect" of combustion gasses leaving the barrel after the bullet has cleared the muzzle.

*** The assumption of linear acceleration here is totally bogus, but it does fit within the use of the conservation of momentum equation. The problem with figuring actual time-based acceleration is having a precise pressure curve, then knowing what the force of barrel friction + bullet obturation is. This is still going to require some assumptions, because you can't precisely measure the time vs. pressure curve with load cells. A properly calibrated piezo could (could meaning "properly calibrated" and applied) get you very close. However, we can precisely determine what the velocity of the bullet is when it leaves the barrel, so that is what the spreadsheet is based on. The best method, IMO, would be to attach an accelerometer to the slide. Then you would know exactly how the slide velocity changes as the bullet traverses the barrel.

So what I did in my spreadsheet is to calculate, based on linear acceleration (assumption is a constant force is applied the bullet and powder mass to move them down the barrel). The counter-force to this acceleration must be an equal and opposite force applied by the system of the locked barrel-slide combo and the recoil spring. The resulting force in both directions turns out to be appx. 2320 lbs., and the bullet would leave the barrel appx. 437 microseconds after this force was applied.

In order for unlock to occur while gas pressure was still in the barrel (i.e., bullet has not left the barrel), the slide-barrel combo would have to travel the 0.210" backwards into the unlock point (locking block) faster than the bullet can traverse the barrel. Applying 2303 lbs of force to the 1.225 lb mass of the barrel + slide, the time it would take to reach the unlock point under 2303 lbs of force (subtracting the 17lb spring force) would be 761 microseconds. If I assume that the opposing forces are terminated as the bullet leaves the barrel at 437 us (neglecting gas jet effect), then my numbers for momentum are exactly balanced.

Here's some interesting observations from this exercise:
- Calculated slide velocity is 26.4 fps
- Changing the spring from 17lbs to 22lbs only changes slide velocity by 0.06 fps. (note that a 22lb spring will decelerate the slide motion much more quickly than a 17lb spring, that's really the only benefit to extra spring force)
- Reducing the slide mass by one ounce increases the slide velocity by 1.42 fps.
- Increasing spring force is not going to significantly delay unlock time. Completely removing the spring in this system makes almost zero difference in unlock time. No spring at all would not cause a KB.
- Mass is critical to control slide velocity, but it takes a huge reduction in slide mass for unlock to occur early. The normal barrel + mass of 19.6 Oz, all other factors held the same, would have to be reduced to appx. 6.5 Oz for KB to occur (assuming this "normal ammo" pressure)
- Slide travel to unlock is critical. In this case, all other things held equal, KB would occur if the distance was shortened from 0.210 to about 0.070" (could the KB round have fired somewhat out of battery/incomplete lock-up?)

I tried all kinds of practical changes to the system to induce an unlock condition, and I couldnt, even at 100,000 psi. Of course, I did make some assumptions on pressure-time curve, and neglected the "jet-effect" of gasses continuing to exert force on the barrel-slide combo.

So, I'm not claiming to be a gun expert, and I certainly could have made errors in my assumptions, especially with the linear acceleration, but it seems to me that the system is designed to never unlock under practical conditions, regardless of the chamber pressure.

OK, flame proof suit is on, fire away!
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Last edited by TDC20; 02-10-2013 at 11:12.. Reason: Change locking block comment!!!!!
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Old 02-10-2013, 15:55   #73
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TDC20, I can't argue with the laws of physics. Your numbers do make some sense with regards to the dynamics involved. We are beating this thing to a pulp as we all scratch or heads for answers...

The slide and barrelremaining locked during the entire pressure event should not cause a blowoutunless, gross lack of case support and the overcoming of the strength of thematerials (brass)...or both.
If something moves to increase the unsupported areas, thenmore catastrophic failure is certain.

I think about proof testing which is required by SAAMI, they test beyond thestandard operating pressures for this test...for the 40S&W & 10mmcartridges their proof pressures would be within 130% minimum and 140% maximumof the MPLM (Maximum Portable Lot Mean)

10mm Service Maximum Average Pressure = 37,500psi

40S&W Service Maximum Average Pressure = 35,000psi

Pressures Values of Proof Cartridges

10mm Minimum average = 50,500psi 10mm Maximum average = 54,000psi max e.v. =98

40S&W Minimum average = 47,000psi 40S&W Maximum average = 50,500psimax e.v. = 92

Data from SAMMI publication 205 http://www.saami.org/specifications_and_information/publications/download/205.pdf

Where these cartridges as loaded, within even these limits or did theysurpass even these pressures? We know from the retrieved load data that theywere over recommended data.
Hodgdon shows simular 165gr bullet with 7.8 grains @ 1185 fps with a pressure of 33,400 psi.

We know case support is always a factor to allow forces to overcome thatsection that is the thinest or weakest...

Will the Brass fail at or above these kind of pressures? At what pressuredoes the Brass fail?
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Old 02-10-2013, 21:46   #74
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[QUOTE=TDC20;19971242]
..... (could the KB round have fired somewhat out of battery/incomplete lock-up?)

... but it seems to me that the system is designed to never unlock under practical conditions, regardless of the chamber pressure.

...[QUOTE]

Thanks for doing the calc. Very revealing. I, too, can only imagine "out of battery" situation.

When I first read, before reading your post, the report at ... http://www.ccfraceframes.com/faq-barrels.html

and looked at the dented frame picture, the first thing that came to mind was 'how could the barrel come into full battery if it had dented the frame so badly?' A KB out of battery would tear up everything BUT the barrel.

On the other hand, an overcharged cartridge would tear up the barrel, and other things.
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Old 02-10-2013, 23:20   #75
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Quote:
Originally Posted by _The_Shadow View Post
Where these cartridges as loaded, within even these limits or did theysurpass even these pressures? We know from the retrieved load data that theywere over recommended data.
Hodgdon shows simular 165gr bullet with 7.8 grains @ 1185 fps with a pressure of 33,400 psi.

We know case support is always a factor to allow forces to overcome thatsection that is the thinest or weakest...

Will the Brass fail at or above these kind of pressures? At what pressure does the Brass fail?
I think that's the question that needs to be answered. Based on my exercise, it looks like there are only 2 plausible paths to the KB. One is where the brass fails under excessive pressure, bursts at the weakest, unsupported point, and blasts hot gasses down towards the mag well. The other would be due to a breakage or other defect causing the locked barrel and slide to be positioned considerably short of the normal starting point when the shot is fired, which then causes unlock before the bullet leaves the barrel and the gas pressure falls.

I got to thinking, the best way to test brass failure would be to use the hydraulic method, similar to how they test scuba and gas tanks, called a hydrostatic pressure test. I'm sure you're familiar with this, Shadow. The idea is that water, which is relatively incompressible, is forced to extremely high pressure using a hydraulic action. If the system fails, there is no great explosion or anything exciting like that, the water just runs out. I think if I remember right, Scuba tanks need to be hydrostat'd every 5 years. I think that is true of all high pressure gas tanks.

Anyway, if a test could be performed on a piece of empty brass while positioned in the chamber of a test barrel, we could theoretically answer that question. I don't have access to that type of test equipment, though. Maybe a university materials research lab could do it. The government may have already done it.
Quote:
Originally Posted by ModGlock17
When I first read, before reading your post, the report at ... http://www.ccfraceframes.com/faq-barrels.html

and looked at the dented frame picture, the first thing that came to mind was 'how could the barrel come into full battery if it had dented the frame so badly?' A KB out of battery would tear up everything BUT the barrel.

On the other hand, an overcharged cartridge would tear up the barrel, and other things.
This never occurred to me before about after market barrels. I'm going to take a closer look at mine and try to determine if they provide the same amount of travel to the unlocking point, and inspect for damage.

The equations for the timing are very interesting. It shows that, as pressure increases and bullet velocity increases, there is still significant margin in the timing in that the bullet leaves the barrel before unlock occurs. I simulated a 3000fps+ 180gr bullet from a G29, and there was still over 100 microseconds of margin! What happens is that the slide acceleration increases significantly under those conditions, but the bullet is traveling so much faster down the barrel that it still clears the muzzle before unlock. I've concluded that for a fully supported barrel, the barrel may actually burst from overpressure before a KB occurs from unlock, unless some other factor significantly reduces the slide travel distance to the unlock point.

I think I saw an AM barrel that did just that somewhere on GT within the past few weeks. It was a fast burning powder that could have been double charged, and I think it was a .45. Of course, there could have also been a stuck squib bullet in the barrel when the exploding shot was fired, too. Still, excessive pressure is excessive pressure. The barrel fragged from the breech end.

I think "we" routinely run handloads over the SAAMI pressure limits in the 10mm. I can't prove this, of course, but I'll continue to believe that brass that is heavily glock smiled was run well over the intended pressure limits, and dangerously close to KB'ing. The fully supported barrels just allow us to "get away with it" for a while. If the Glock barrels can handle proof loads in the 50kpsi range, then I imagine some hand loads I've read about here are well in excess of that. A lot of folks used to pooh-pooh the results of Quickload software in predicting pressure for some popularly accepted loads. Maybe Quickload is closer to the truth than we wish to admit?
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