Kaboom!

[OlongJohnson]

The most likely is a ring of crud or lead at the chamber mouth. Visual inspection revealed a lot of crud there (embarrassing...). So, I used Kroil on a bronze brush on a drill to clean it.

No issues in 2000+ rounds since.

So you're saying guns actually do need to be cleaned every once in awhile. Probably.

[Clusterfrack]

So you're saying guns actually do need to be cleaned every once in awhile. Probably.

Hahah! Yeah. Probably. But seriously I do clean my guns, including an hot ultrasonic bath, barrel brush, etc. about every 3-4000 rounds (match guns more often). However the crud at the chamber mouth requires direct attention.

[BN]

However the crud at the chamber mouth requires direct attention.

What created this crud? I remember back when I shot a lot of LSWC in a 45 that I had a chamber brush on a short handle that I would spin in the chamber every time I cleaned. I don't do that with my 9's. I shoot Bayou coated bullets.

[Clusterfrack]

What created this crud? I remember back when I shot a lot of LSWC in a 45 that I had a chamber brush on a short handle that I would spin in the chamber every time I cleaned. I don't do that with my 9's. I shoot Bayou coated bullets.

Great question. My best answer is fuck if I know, but here are some possibilities:

1. >35,000 rounds without directly cleaning that area. My main cleaning procedure was a brush, then jag and patches until the barrel looked clean.

2. Lead from a shaved bullet. I use Blue Bullets, and don't have many problems with that, but it happens.

3. Accumulated polymer bullet coating.

4. Brass shavings.

5. Unicorn shit. My Shadow2's have been so reliable that I took it for granted and assumed they always would be.

All I know is now I am using a bronze brush on a drill, and Kroil to scour the chamber when I clean.

[BN]

https://shopwilsoncombat.com/Chamber...info/803%2D45/

This is what I used. Looks like they used to make a 38 super brush at one time.

[NPV]

This type of thing is not isolated to personal reloads either I had it happen with factory ammo. Your CZ faired much better than the G19 I had at the time. I’ll echo what another poster in the thread said, Oakley M2s are great. It’s unfortunate but it took an event like this for me to learn the importance of having a first aid kit in my range bag.

I’m glad to see your ok OP.

[Clusterfrack]

Yikes! That is scary. Hope you weren't seriously injured.

This type of thing is not isolated to personal reloads either I had it happen with factory ammo. Your CZ faired much better than the G19 I had at the time. I’ll echo what another poster in the thread said, Oakley M2s are great. It’s unfortunate but it took an event like this for me to learn the importance of having a first aid kit in my range bag.

I’m glad to see your ok OP.

[willie]

My opinion is that the op's mixed brass is the culprit. Among the immense 9mm universe can be found much variation in brass. Case dimension such as overall length, rim thickness, case wall thickness, and case head thickness varies within brand and from one brand to another. Shooters bask in the glut of cheap 9mm but may not realize that companies will and do sacrifice quality to remain competitive. This effort to reduce cost could result in charges in the composition of the brass case itself. We must remember that manufacturing brass that is excellent for the reloader's purpose is not one of their aims.

In kaboom events, it appears that the pistols are unlocking early. Stock CZ 75 series pistols have a heavy recoil spring and a heavy hammer or main spring. Now I will make a statement that some will surprise some. Of the two springs, the hammer spring plays a much greater role in reducing slide velocity. Further it has a significant role in delaying unlocking of barrel and slide in that the interaction of hammer spring weight, slide weight, and the locked breech mechanism itself work together. Reducing hammer spring weight changes a significant variable.

We know that some custom pistols have reduced hammer spring weight in order to have lighter trigger pulls. If the op's CZ has a much lighter hammer spring in addition to a lighter recoil spring, then reduced spring weight might contribute to the early unlocking. I say might. Cajun Gunworks sells a superior product. I am not qualified to criticize their work. I wil ask the op if he is replacing his springs at certain intervals.

[Clusterfrack]

@willie, all good points. I don’t think either is what happened.

The 2 kabooms happened in my practice gun, and not my two match guns, which also shoot the same mixed brass. The match guns also have lighter hammer springs. I’m using fairly heavy recoil springs in all the guns (13-14#).

I use a Hundo case gauge, and that would catch out of spec brass.

Hopefully the clean chamber will prevent another event. Time will tell...

[willie]

You have a good method for chamber cleaning. If you have not tried Chem Tool, available at auto parts stores, you might buy a can. It's pressurized. Since you are removing the barrel, spraying the chamber might be a quick remedy. I have found that this stuff is a powerful solvent. I have used it to remove stubborn gunk from revolver chambers. Chem Tool is a useful solvent. I like the Kroil product that you mentioned. Effective and safe. When in doubt, we can spray with Kroil.

I think you have resolved your problem. I had never heard of chamber crud bringing about kabooms but understand how it could. Last year I visited David at Cajun and his crew when passing through their town. They are as kind, gracious, and courteous as they are knowledgeable. His shop was immaculate and organized. It is a small family operation. These folks can detail strip a CZ as rapidly as I can strip an 870. If they have a Dremel tool, then it's kept in a padlocked closet. I saw small files and stones.

You shoot a lot. Can you hit cans or rocks thrown in the air?