Home Forums Hunting & Shooting Gunsmithing BRNO ZH304 locked up after firing.

No problem firing with combination 7X57R over 12 GA barrel set. Removed that, installed 20 ga O/U set, and went to the range.

Loaded two rounds of Rem target loads. Fired front trigger and opened to check which barrel had fired. Action would only open part way. Top barrel had fired.

Didn’t want to bring gun home with live round, so closed action and fired rear barrel as well.

Tried everything but still not opening. Tried half dozen times to remove the barrel set, and it will not come out.

Removed the buttstock, and gave whatever I could get to a dose of WD40. I know better, but that’s all I have here at the moment. Letting it all rest until tomorrow.

Okay, Gentlemen, what are your thoughts on this? Broken firing pin? If so, how do I get to it on this BRNO.

Thanks for your help,
Ted

Where is this gun made at ?? Are you shooting 2 3/4 shells? If it only opened 1/2 way, maybe something to do with the cocking mechanism. If you shake the gun, can you hear something loose sounding?

Did it start to extract the first fired round when you cracked it open? Might be a tight case/shell? If it is a tight shell then cleaning rod ram rod might assist.

Shooting factory 2 3/4 inch loads.

No sign that the shell is extracting when partly open.

Here’s a link to the operation of the gun. Not my video.

Ted

Okay, mauserand9m, you had the correct answer.

A little persuasion in both tubes using a solid brass rod saw the action opening a bit each time until almost there, and then locked up again. The employment of a light finish carpenter’s hammer completed the job.

Here’s the evidence!



Obviously, the shells were stuck in the chambers.



Thanks to both you and Alan_C. Please carry on with the diagnosis…..

Ted

Shoot some low base loads and study

For sure!

Posted that I had shot target loads, but they were full house. Was thinking about the 12 gauge under the 7X57R barrel set that I use for grouse and ptarmigan when hunting moose and caribou. That I use #7 1/2 in the I/C barrel.

Must be a rusty or scratched chamber to hold fired rounds that tight. Big cleaning and polishing, right?

Ted

Today’s economy shot shells are notorious for hard extraction because of the use of plated steel in place of brass for the base. It will help to polish the chambers but switching to premium shells such as AA’s will make things much better.

I can't think of any European company that loads that heavy of a 20ga load and from my experience it really isn't needed. An ounce of lead shot is plenty it is my go-to for in 12, 16.and.20ga for birds. High steel 2 3/4 cases even get stuck in my reloader.

I think your problem is heavier loads and high steel hulls.

I shoot a BRNO 305 12/5.6x52R with a set of 12/12 skeet barrels.

No doubt you are correct. I'm not worried about the action being strong enough, as it is designed to handle center fire rifle cartridges that operate at four times the pressure of shotgun ammo, but never considered steel bases being a problem.

Will try some brass base slug and some low base target loads.

Thanks!

The action is strong enough but the extraction is the problem even rifle shells for it are tapered much more than a shotshell.

No worries, here to help. Glad to see that was the problem and not something more complicated with the internals.

As an aside, I've seen a Merkel double lock up due to extrusion of the primer into the firing pin hole as a result of combination of sloppy firing pin hole and hot loads. The rifle was in 7x65R and the loads were hot to get the velocity to regulate properly. Forcing it open (it wouldn't open at all under normal effort) sheared the primer extrusion off and got it open. That Merkel went back for proper attention but I don't know how it ended up - the gunsmith was consulting with the factory. Using hot loads is not a good strategy. It's a pity, the Merkels normally regulate well at normal type loads.