Home Forums Hunting & Shooting Combination Guns and Drillings Zoli 12ga over .222 -- Rifle Headspace issue?

I'm looking for some feedback on the image below of the flattened primers fired in the new-to-me (was bought used) Angelo Zoli (not "Antonio") 12 gauge over .222 Rem combination gun. The receiver is nicely engraved and the gun is in excellent condition, and as it came with the very expensive Valmet quick-detach rail-mount scope mount along with a decent 1.5-4X scope mounted on it (all for a really nice price!) -- I'd really like to solve this issue and get the gun working well.

The (3) fired brass shown in the image all shot well -- grouping into 1/2" at 50 yards when using an informal rest.

The image shows (1) Hornady "Super Varmint" factory loading unfired brass, followed by (2) fired brass to the right. The bottom row shows (1) Remington factory load unfired, followed by (1) fired brass to the right. The primers of the fired Hornady brass look more flattened than the Rem brass, as you can see the rounded edges of the primer cups are more like sharp corners after firing; and the the primers cups on both makes of brass don't show the typical dimples that you'd see on once-fired brass -- and it appears the dimple has flowed back against the firing pin.

Since they're both factory loadings, I'd suspect this Bockbuschflinte has excessive headspace and it might become a "reloads only" project for me so I can adjust the brass to fit the chamber. (Luckily, I do load for the .222 Rem.) I could send the unfired & fired brass back to both Hornady and Remington for evaluation (as was suggested by a shooter at the range), but I don't think it's over-pressure -- and I'm more inclined to look at the lower .222 rifle's chamber first.

* Any other thoughts on the likely cause of this appearance of the fired brass?

* Should I also check the condition of the rifle's firing pin tip, or return spring?
(As it does drag on the fired brass and one shot was hard to open after firing.)

* Or, could the hammer spring be weak?

Thanks!

Old No7

I'm certainly no gun smith but I would look at the firing pin itself ???? If its dragging when you open it sometimes it must be sticking in the primer ??? Look for simple stuff first then dig deeper. GWPGUY. 🐾👣🇨🇦

Thanks, this is what I've checked out so far...

* The gun has internal hammers with robust coil springs, just like you'd see on a Citori
* Both firing pins have nice, rounded tips; with the shotgun pin 1.5X or more the size of the rifle's pin
* There are no burrs on the firing pins, hammers or spring struts; all looks good inside the receiver (and looks well-made too)
* The firing pins do rebound, as they have to (to be pulled away from the breech so the barrels can tip down)
* The firing pins don't hit straight on as on a bolt action, but come in on angles from the side and elevation
* Unfired factory loads, with the extractor removed, fit flush to the breech face (so I don't think there's any excessive headspace)
* Neither factory bullet engraves the rifling when chambered; they sit flush but not tight
* Fired brass measures 0.002" larger than the unfired ammo just about the extractor groove (as several online articles say to watch out for brass that grows by 5 thous' or more (0.005") as being over-pressure loads_

Based on all this, I'm inclined to believe that the primer flow is a function of the top-break design with the rebounding firing pins (which are pulled away from the breech face, as they sit roughly 1/16" below the face of the breech after "firing").

I'll try some handloads which work well in my Rem Model 700, but using different primers, to see if the primer flow can be reduced any.

Old No7

How much does the protrusion of the firing pin measure?? Other than that???? Maybe try Remington 7 1/2 primers ??? Try google, or talk to a real gunsmith. Good luck. GWPGUY 🐾👣🇨🇦

Personally I do not see a headspace problem or any concern with the fired cases. I think your logic is spot on with regard to the rebounding firing pins. I would work up a load using harder magnum primers, might very well stop the flow.

I would suggest you try handloads using (white box Winchester #41 or CCI #41) the military spec primers designed to prevent slam-fires in the 5.56 ARs. The harder primer cups could reduce the metal flow back into the firing pin dents. If, as you say, the mainsprings are robust, it still should fire reliably.

If it were a bolt rifle I would be looking hard at the firing pin spring, as a weak spring there can allow what you are seeing in your primers. Being a break-action, though, the firing pins have to rebound or retract to allow you to open the action.