When I say I'm an OCD dry firer, I wouldn't be surprised if I pulled that trigger 50,000 times. I was buying cool gear on a grad student stipend, so I couldn't really afford to shoot that much. 

I cant believe that the prevailing theory here is that dry firing is cracking the slide. You will never create the force with dry fire or racking the slide that you will with the discharge of an actual round. We even had post where a guy said his was from live fire.

Do we think its more likely that this is caused by dry fire and racking the slide? Of that every once in a while metal has flaws in it and is prone to break or crack?

There is a difference in dry firing to disassemble and dry fire practice.

If I remember correctly Gabe White said (on P-F thread) that he cracked a glock breech face even using snap caps. He is an animal though, so that is a huge amount of reps

I ordered the dryfire mag. Kind of expensive for what it is, but I have played with one before and it seemed to work really well. I'll post about it once it arrives. 

The theory of the striker assy hitting the rear of the breach face when no primer is present to restrict its travel seems plausible to me with a high number of reps.

And punches out the breach face the same size and shape of the back of a round of ammunition. Is it more plausible that a weaker piece of metal and a spring break out a stronger piece of metal or that flaws in metal over time give way during live fire.

There was a post by a member stating that his was from live fire, but that was over looked because it didn't fit the "theory" that the cause is dry fire.

You could try asking in this thread:  https://www.ar15.com/forums/handguns/High-round-count-pistols-100-000-observations/4-160140/?page=1

They have broken a bunch of Glock slides from live fire, but to my knowledge they have never cracked a breech face.  But I haven't read through all 15 pages...

Perfection ??????

There was also a post by a member saying he heard this was an issue in a recent Armorers class specifically talking about a large foreign PD.

If this is true have that member post the contact info for the instructor, I'm betting this will turn into "someone told me they heard this". Words are cheap on an internet forum.

I guess the majority of people in this thread are determined to believe that they must spend money on pointless tools that are used when the gun is under less stress than when it does what its designed to do.

How many millions of Glocks have been sold? We have a dozen examples of this happening? I find more pictures and talk of out of battery explosions online than this, which is far more dangerous. Keep in mind that this is the widest used LE duty gun out there, which means its the gun that likely gets tested the hardest. I can tell you that in my state dry fire is stressed and currently in practice and we have never heard of this. Again, we do have failures in all of the guns we use. In our Glocks we see common parts that break and we have seen weird ones (cracks on the side of the slide at the ejection port, cracked frame), but what we didn't do was over react to a very rare occurrence. We contacted Glock, they replaced it, and we continued as business as usual.

Just unholsted my 19 to look at it out of curiosity.

Jesus.
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It’s a gen 3 I bought lnib. Under a thousand rounds on it and I don’t sit around dry firing it.

@randomshooter Are you referring to the crack behind the extractor?  Pretty sure all have that. My BNIB G17 does along with 6 others.

yes. Upon closer inspection it isn’t a crack

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Guy from glocktalk
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Happened to my Glock and I posted about it in here.  Pretty much the same type of crack.  

I had done maybe a couple hundred dry fires in the time I owned it.  

Glock replaced it, but stated they wouldn't replace it again.  

My archived thread here:

https://www.ar15.com/forums/handguns/-ARCHIVED-THREAD-----updated--Pistol-back-from-Glock---G19-slide-cracked/13-154930/?page=1


Picture of the crack is near the bottom of page 1.

Not to start a pissing war or anything, but this has been pretty well known in the shooting sports community for a while. LE majority barely use their pistols and don’t see the kind of issues heavy users do. 

Glock does recommend the use of snap caps for dry fire practice. 

So , Glocks are now blowing up without any ammo?

While it may be well known that it happens, I don't believe its as common as some people think or imply. There are much more common failures. You are right, a good number of LE shoot a few hundred rounds a year. But here are also a good amount that shoot much more than that, some probably close to 20k rounds a year. We also see several academy classes a year which includes approximately 2k live fire and lots of dry fire and manipulations (With several types of guns).

I understand that Glock recommends the use of snap caps for dry fire practice, that doesn't mean its to stop this type of failure.

I'm also not trying to start a pissing match. I simply posted on this thread to try to share a little info. Info that is based on a lot of time on the gun, working on the gun, and teaching others to use the gun.

What seems to be the common factor when this particular failure happens, is the owner dry fired it a lot without snap caps. Like 30,000 times. It appears that the striker impacting the back of the breech that many times is what causes the crack. 

Common factor.... except the quote above.

What else was common? Fired live rounds?

How about the millions of guns out there that are dry fired that don't have this happen? I think were forgetting that to did-assemble the gun you have to pull the trigger.

I think the above user is the first person to mention the broader use of snap caps. To protect the firing pin.

Call me crazy, but I don't know many people that have disassembled their Glocks 30,000+ times.  Metal will stress as its used and I bet that the slide is engineered to take the pressure from the firearm firing and bleed the impact through the base of the round that is larger in surface area then the firing pin into the breech face as the recoil spring engages and the slide comes back.  This is a completely different type of force then a firing pin impacting the back of the breech face and that force having nothing to bleed off the energy from the firing pin.  It doesn't sound like a lot of force, but over time it will fatigue the breech face and cause the issue.  The fact that there are a couple of breech face failures from live firing compared to the larger number of breech face failures from dry firing is enough to lead me to understand that dry firing might be an issue over time.  This is also well over what the majority of the populations firearms will ever see.  Is it as common as springs failing from live fire? No.  But it is something that people that are doing large amounts of dry fire should be aware of.

This is why you dry fire with an object in the breech face to keep the slide out of battery.

The point I've been trying to make the entire time is you don't know it was dry fire. You assume it. The only way to truly figure it out would be to inspect the damaged guns and get a true count(not just what people remember) of rounds fired and dry fire. Looking at how dirty the original posters gun was (and likely most guns that are shot heavy), we cant say exactly when it cracked.

Theres to much bad info in these forums that are backed by nothing more than an opinion. For some reason people want to jump to the most shocking possible cause, that my gun could break while dry firing! (Dramatic pause).

Also, if the slide was out of battery due to a snap cap it would not fire.