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Discussion Starter · #1 ·
This is a bit of advice I hadn't heard before. Repeatedly chambering the same round back into your autoloader can be a very bad thing.

"Set-Back" Suspected

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What is commonly known, and is referenced in the report, is that continuous loading of the same round(s) will eventually create an excessive pressure situation as the projectile is driven deeper into the case due to repeated contact with the feed ramp under force. As a .45 ACP round operates in the 21,000 psi range, projectile set-back may not create an over-pressure problem. When the S&W .40 cartridge, which operates at the 31,700-33,600 psi levels, several thousandths of set-back could generate enough of a pressure spike needed to disassemble the pistol.
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I've heard that rotating the carry ammo is a good idea, but this states that using the same cartridge to charge the chamber over and over can drive the bullet deeper into the casing, eventually causing an over-pressure situation. Yikes!
 

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Very good advice indeed. Beyond the set back issues, you can also get worn out brass that will not eject properly after the first shot. Also, you tend to touch that same round a lot which will result in more gunk in your gun and on the bullet itself.

On the other hand, you probably shouldn't cycle all the bullets in your magazine too often either.

I've got into the following sequence:

1. Chamber the same round for anywhere from a week to a few weeks. However, I rarely unload my gun, so it's not as big an issue for me as it would be for those that load/unload every day.
2. Go shooting. At the end of my range time, I'll re-chamber 'the' round, put in my defensive load magazine, then shoot it. This gets rid of the round and allows me to ensure that my carry ammo will chamber correctly.
3. When I get home, I pull a fresh defensive bullet (currently Winchester Black Talon) out of the box and put it in the top of the magazine.
4. Cycle the magazine ammo (top to bottom) maybe twice a year and inspect the bullets before putting them back in.

About the worse thing you can have happen is the first bullet of your defensive load to fail when you most need it.
 

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How does this apply to those who re-load.

I don't but I have friends who have re-loaded the same brass many many times. :shock:

tarzan
 

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Discussion Starter · #4 ·
This has nothing to do with "reloading".

What it's talking about is unloading your gun, then loading it again by chambering the same round again. It is the action of that same round hitting the loading ramp over and over that drives the bullet deeper into the casing, which causes the risk of a dangerous overpressure.
 

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Jeff Johnson said:
This has nothing to do with "reloading".
Well, you can get the exact same thing if you reload improperly and seat the bullet to deep. Also, if you don't crimp tight enough or use old, weaker brass, your ammo can be more prone to what is described above.
 

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My Department was just informed of this a few weeks ago. We were also told that some gun manufactures are now saying it voids the warranty to continually rack the same round in the chamber.

I'm still trying to find the bulletin we were sent about it.
 

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What I do in the rare occasion I unload my gun, is lock the slide to the rear with the mag. out and place the round in the chamber by hand. Then release the slide. From what I see this will prevent the round from hitting the slide ramp. Then once it’s loaded I insert a full mag.

Maze
 

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Mazellan,

Unfortunately, the occasional method you use may, depending on the pistol, excessively stress the extractor and cause premature failure by forcing it to climb over the case rim. Climbing over the case rim requires more movement of the extractor than when the case rim just slides under the extractor as it is fed from the magazine.
 

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Oookay.... Now explain that in plain english?? lol Im not sure excactly what the failure would be. A fail to fire? A failure to eject? Sorry I just don't understand what you mean.

Maze
 

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I've seen a lot of .40 and .357 Sig rounds with way too much setback after repeated chambering.

What's great for causing this is malfunction clearing drills where you intentionally induce a double feed.

When training the tap, rack portion of the drill that should be second nature any time you have a malfunction, that second round REALLY gets hammered. I've seen guys pick them up off the deck and go to re-use them. No thank you.

I've also seen many rounds where in the process of clearing a double feed the ejector of the pistol punches a hole in the side of the casing during vigorous racking to clear a jam.

I don't pick up cartridges off the deck, ever, and whenever possible in training I look at them while loading.

Yes, you have to practice doing it blind, too - but regular reloads I try to look. If you are cognizant of the issue it becomes quite easy to eyeball rounds that don't look right.
 

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Jeff Johnson said:
This has nothing to do with "reloading".

What it's talking about is unloading your gun, then loading it again by chambering the same round again. It is the action of that same round hitting the loading ramp over and over that drives the bullet deeper into the casing, which causes the risk of a dangerous overpressure.
I seeeeeeeeeeeeeee said the blind man as he fell down the well,
 

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Mazellan,

I was referring to extractor failure. For example, I've seen many references to the method you described causing extractors in 1911-style pistols to break. In normal operation of the 1911, as the slide moves forward it picks up the next round from the magazine. The rim of the case slides up the breechface and under the extractor hook, with very little actual flexing of the extractor. If the extractor has to engage the rim of a round that's already chamber, it results in a lot more flexing of the extractor and, possibly, premature extractor failure.
 

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Here is a quick test I did... I took a new Independence round and chambered it several times without the use of a magazine, measuring it after each loading. My goal was to see if I could make it shorter than 1.100"

New Independence round factory length. 1.120"

Here is a new Federal Self Defense Round just for reference. Also 1.120"

Chambered 0nce: 1.117"

Two: 1.115"

Three: 1.112"

Four: 1.108"

Five: 1.105

Six: 1.1025

Seven: SUCCESS! 1.099


As you can see this round is officially junk. As I was doing this, I noticed the sound of the round going in getting worse. I believe this was the sound of the extractor slamming against the back of the cartridge.
 

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Wow! Excellent work SGT Jensen. That's a bit scary if it set back that easily. This was the Glock 23?

Wait, you chambered it without the magazine? That's probably a bit unfair as it's actually the contact with the ramp as the bullet exits the magazine that will cause the setback in actual conditions, so not using the magazine probably doesn't best represent actual offset
 

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apollosmith said:
Wow! Excellent work SGT Jensen. That's a bit scary if it set back that easily. This was the Glock 23?

Wait, you chambered it without the magazine? That's probably a bit unfair as it's actually the contact with the ramp as the bullet exits the magazine that will cause the setback in actual conditions, so not using the magazine probably doesn't best represent actual offset
I thought about this after the fact, so I will be trying this again using the magazine. Yes, it was with my G23.
 

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SGT Jensen said:
I thought about this after the fact, so I will be trying this again using the magazine. Yes, it was with my G23.
I predict the results will be quite similar. I've seen it myself with G23, G27 and several different Sig models. I do not believe it has anything to do with the pistol brand, nor do I think it's the pressure of the extractor snapping over the case rim that's doing it.

It's the breech face shoving the bullet against the feedramp.

Of course I'd love to see your test photos and data done out of the mag, same pistol, same ammo for giggles.
 

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OK, did another test, with very similar results. Same Independence ammo, same G23. This time I let the pistol load the round from the magazine, as there are some speculations as to whether or not this had anything to do with the results. Remember, the round measured 1.120 when I started.


One - 1.118

Two - 1.115

Three - 1.112

Four - 1.109

Five - 1.107

Six - 1.103

Seven - 1.100


On the first test when I put the bullet in the chamber and let the extractor hit it, it measured 1.099 after seven times. This is only + .001 difference using the magazine.
 
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