Muzzle flash...from the chamber?

[chris in va]

Maybe I'm hallucinating, but lately I've noticed substantial flame coming from the breech of my CZ 97b using my LRN reloads.

Do I need to use a stronger recoil spring to help keep the slide closed longer? I'm not using hot loads, 5.5 7625 under a 230gr LRN. I have the spring but last time I used it the gun started malfunctioning.

On a side note, I've been getting a few of these as well...



I don't think its the mags as they are MecGar and it happens with all of them.

 

[rcmodel]

A stronger spring won't hold the slide closed longer.

It could be your load is light enough you aren't getting a good case seal and flame is blowing past the case in the chamber??

Are you getting a lot of smoke on the fired cases?

rc

 

[chris in va]

Hey RC.

Not really any soot, certainly nowhere near what my blowback CX4 does to the cases. I've been using this formula for a few months with few issues so the 'bolt over' stovepipe issue and chamber flash are something new.

 

[Rule3]

You are at the min powder load per Hodgdon. Try bumping it up some.

You mention something about a spring?? But what?

Is it the original recoil spring? How many rounds are on it (approx)??

My guess is it's not a hot enough load to cycle the gun properly

Use the Max of 6.0 grains but don't seat it to Hodgdons 1.200 where ever they came up with that! Use the plunk method. Hodgdons loads are not known to be excessive.

 

[rcmodel]

but don't seat it to Hodgdons 1.200 where ever they came up with that!

They came up with that by using Hornady 230 grain flat-point bullets on the jacketed data.

The don't say if the lead bullet load is also a flat-point, but it must have been??

rc

 

[Rule3]

Discontinued bullet. Still seems short.

 

[chris in va]

CZ's have a super short leade, so I have to load the Lee 228 bullet to 1.22 so it passes the plunk test. It's frustrating Lee makes their ogive so darn fat right off the nose. It looks nothing like a normal 230gr FMJ profile.

 

[Slamfire]

These charts are from Chinn’s The Machine Gun, Vol IV. Go take a look at the sections on blowback operation and gas operation here at http://www.ibiblio.org/hyperwar/USN/ref/MG/
I can’t think of a single blowback, delayed blowback, or gas operated mechanism that does not use the residual blowback effect in its timing. These mechanisms are designed so that unlock occurs at a low enough pressure that the case does not rupture, but that there is still pressure to keep things moving.

This is also a good reason not to use slow powders in these mechanisms as pressures at unlock will be too high causing function issues.




So given that there is some small pressure at unlock, you would expect some hot gases to come out of the breech after the case is extracted. This is simply a nuisance, but you can experiment with different, and may I suggest, faster burning powders, which will reduce flash.

This blowback mechanism was used in the Polsten 20 mm cannon. This cannon was used in a land based turret mechanism and according to Brassey’s, venting of un burnt propellant in the crew compartment was a concern. This unusual blowback mechanism must have had a slow cyclical rate, which means a lot of dwell, so when the breech finally unlocked, hardly any gas vented into the turret. Besides the rebated case head, this required greased ammunition or the case would have been stretched in half during extraction.

 

[Rule3]

CZ's have a super short leade, so I have to load the Lee 228 bullet to 1.22 so it passes the plunk test. It's frustrating Lee makes their ogive so darn fat right off the nose. It looks nothing like a normal 230gr FMJ profile.

Yes they are. I have the same problem with My 9mm Custom. Only with RN lead bullets. Regardless I still think it's a low powder charge not cycling the pistola.

 

[n6yga]

Chamber flash? Could be the gun is firing slightly out of battery? Henry lever-action rifles can do that sometimes. At least in 22LR. I have seen it.

Just spit-ballin' here...


Mark.

 

[chris in va]

I'll try bumping it up to 5.8. Hodgdon has max at 6.0 so hopefully it'll 'fix the glitch'.

7625 wasn't my first choice, it was all they had left and I haven't seen a pistol powder since I bought the jug 6 months ago.

 

[Rule3]

I'll try bumping it up to 5.8. Hodgdon has max at 6.0 so hopefully it'll 'fix the glitch'.

7625 wasn't my first choice, it was all they had left and I haven't seen a pistol powder since I bought the jug 6 months ago.

If your powder measure is accurate and you do not seat the bullet below 1.200 just live life in the fast lane and load a few at 6.0 grains also in case the 5.8 does not work.. With a lead bullet you are not gonna blow anything up.

Notice the max of 6.0 gr is the same for the FMJ as it is for the lead