taurus KABOOM!

bearandoldman · Post by **bearandoldman** » Fri Aug 06, 2010 10:11 am

Got to agree, those are some great pictures Hak, must have had some awesome pressure to flatten the primer that good and extrude it into the firing pin hole like that.
Kaz, I am an old fan of Green Dot and Unique from my old shotgunning days, they are very versatile powders and soften the recoil of most shotgun loads. I used to use it because you could load 12, 16 20, and 28 gauge with it also use Green Dot for .38Sp and .45ACP and probably can be used in a lot of other cartridges like .44Sp or .45LC and who knows what else. It is a bulky powder and fills the case well, that is why it works so well in shotguns. If I remember correctly, I use 5.8 of Green Dot in my .45ACP and 4.6 in my .38SP. I believe I tried to double load a .45ACP one day to see how much it filled the case and I doubt if you could get the bullet seated as it fills the case almost to the top.

Post by **Bullseye** » Fri Aug 06, 2010 1:06 pm

Too little powder caused it to detonate all at once instead of burning at a controlled rate causing the case overpressure.

R,
Bullseye

Georgezilla · Post by **Georgezilla** » Sun Aug 08, 2010 2:49 am

Bullseye wrote:Too little powder caused it to detonate all at once instead of burning at a controlled rate causing the case overpressure.

R,
Bullseye

That makes a lot of sense. I am glad that you explained why under-charging can overpressure.

I've read a few reloading books and they all mention that under-charging a case can cause over-pressuring, but none of them mention why. If memory serves, one of the reloading books I read even noted something a long the lines that under-charged cases causing over-pressuring was a "scientific mystery." I thought that statement was a bit odd...

Post by **Bullseye** » Sun Aug 08, 2010 11:02 am

Georgezilla wrote:
a "scientific mystery." I thought that statement was a bit odd...

Take that from the article's author to read: "I have no clue as to why it works that way but I'll comment on it anyway."

Think of the powder charge in a casing like a fuse, it burns at a steady rate away from the source of ignition. If a fuse burned all at once then the charge at the end would detonate at an inconvenient time (i.e. when you wouldn't want it to). The primer is the ignition source in a cartridge and the case contains the powder that is to be consumed. In a casing filled within prescribed limits, the powder starts burning on one end and follows through to the other. During the powder's burn time the bullet is also moving down the barrel. The powder increases pressure at a linear rate (also known as the burn rating of the powder) and this is what keeps the cartridge from becoming like a stick of dynamite and turning a pistol into a hand grenade. If all the powder burned at once the expanding gas pressure will increase at a rate beyond what is prescribed and it has to expand somewhere, that is what causes the brass casing to give or "blow out".

Hope this helps describe the process a little better.

R,
Bullseye

Georgezilla · Post by **Georgezilla** » Sun Aug 08, 2010 2:12 pm

Thanks very much for the detailed explanation, Bullseye. Ever since I started reloading, not knowing why this phenomenon happened has really bugged me.

I knew that the reason why under-charging causes over pressuring was beyond my own knowledge scope. But given all the scientific things society can do, I was amazed that an expert would go so far as to say it was a mystery. I think you are right about the author's train of thought.

bgreenea3 · Post by **bgreenea3** » Sat Aug 14, 2010 4:33 pm

I had a thought on this one the other night while at the reloading bench.....

...the case failure could have been from a flaw on the case that I may have overlooked, a dent, ding, or week spot, and not because of over/under loading.

greener · Post by **greener** » Sat Aug 14, 2010 6:18 pm

We may never know. One of these days, I'm going to get some lead round nose and see how the Taurus reacts. Worked ok in the past, but I've shot mostly semiwadcutters lately.

Hakaman · Post by **Hakaman** » Mon Sep 13, 2010 7:36 pm

I know this is a late post, but to my knowledge, the 1911 doesn't seem to support the case as well as some of my other hg's.
Haka

Post by **Bullseye** » Tue Sep 14, 2010 6:49 am

Hakaman wrote:I know this is a late post, but to my knowledge, the 1911 doesn't seem to support the case as well as some of my other hg's.
Haka

A properly sized chamber and throat fully support a 1911 cartridge case. An improperly sized one can leave the case vulnerable to blow outs when the case wall is unsupported. A sure sign of an improperly sized chamber or throat is bulged spent cases.

R,
Bullseye

Hakaman · Post by **Hakaman** » Tue Sep 14, 2010 6:46 pm

A properly sized chamber and throat fully support a 1911 cartridge case. An improperly
sized one can leave the case vulnerable to blow outs when the case wall is unsupported.
A sure sign of an improperly sized chamber or throat is bulged spent cases.

Well, I did some checking on my own, and the following are photos of various hg's I own,
with a representation of their head spacing.
The list below is reflected left to right, as a book reads:
Beretta M9A1 Pro
Taurus PT1911
S&W m&p Pro
Glock 34 Stock
Glock 34 After Market (KKM Precision)

It can be somewhat difficult to show the case support because camera angles may be deceptive. I have tried to as non partial as possible.
My opinion:
The Glock barrels, even the after market KKM, have the worst case support, no doubt.
The S&W m&p Pro has the best case support, no doubt.
The Beretta and Taurus PT1911 are somewhere in the middle.
Hope this helps,
Haka

Post by **Bullseye** » Tue Sep 14, 2010 8:06 pm

I'm guessing by your response that you don't concur with my original statement. Take a close look at the PT1911 barrel, just because the barrel doesn't go all the way to the case bevel doesn't mean that the case is not fully supported. A .45 ACP case is not straight walled. The brass is actually tapered near the bottom. This thicker case wall also provides support for the casing, it is when the thin part of the case wall is exposed that a case is considered unsupported. When you combine the thin wall exposure and a high cup pressure, like those found in many 9mm and 40 S&W cartridges, that you see evidence of case fatigue through bulging. In a .45 ACP cartridges , the cup pressure is relatively low, compared to the other cases, and that combined with the greater wall thickness near the base adds support to the case. It is when someone over throats the barrel feed ramp or doesn't check for proper head spacing that a .45 ACP case can be woefully unsupported.

R,
Bullseye

Hakaman · Post by **Hakaman** » Tue Sep 14, 2010 11:27 pm

I'm guessing by your response that you don't concur with my original statement.

I wasn't directly disagreeing with your statement, but when I bought my Glock 34 after market barrel I realized the the barrel (throat) wall didn't fully support the case. I started looking at all my hg's to see how they matched up, and noticed the 1911 was about the middle of the road, so to speak. I also realized that the wall thickness is greater at the bottom of the case, but never thought that a shooter could depend on that aspect. I guess I learned something. I think the 9mm is also tapered at the bottom as well, I think ? I also realize that the 45 acp is lower pressure then 9mm an 40 S&W, and that's why people like the 45acp to reload with. I think the 38sp is the best of both worlds, except when you under load it, like I think I did, as shown in the earlier post in this thread. I thought that near to taking off the top strap followed by half the cylinder. It is amazing powerful when a round blows under loaded.
Haka

Post by **Bullseye** » Wed Sep 15, 2010 5:28 am

The cases of 9's and 40's are also tapered but their case walls are far thinner than the .45ACP cartridge. Combine that with the significantly higher cup pressures found in those cartridges and throat depth is much more critical for case support. If you see any signs of bulging near the base of a case it means the throat is too deep and the barrel is not providing adequate support. Reloading a cartridge that has a bulge in the case means there's a greater chance for a blowout because the case was weakened where the bulge occurred. A sizing die will reshape the bulged case but it cannot strengthen the metal where it was fatigued by the stress of overpressure and lack of support. This is one reason to carefully inspect brass before the cleaning stage, and be especially wary of range brass that may have been scavenged because someone else's pistol may have an improperly cut barrel.

R,
Bullseye

Hakaman · Post by **Hakaman** » Wed Sep 15, 2010 1:33 pm

it means the throat is too deep

What is meant by the above statement?
thanks, h

Post by **Bullseye** » Wed Sep 15, 2010 5:27 pm

The throat is the curved portion of the barrel where the round enters the chamber, sometimes called the barrel's ramp. If you see a lot of bulging in your spent brass that usually means that beveled edge is cut too far into the chamber. Being cut too far means the case is not supported properly and the detonation pressure is bulging out the brass.

R,
Bullseye