Zoli 12 ga over .222 Rem -- Flattened Rifle Primers issue

[Old No7]

Help needed from our most experienced reloaders!

I'm looking for some feedback on the image (below) of the flattened primers fired in the new-to-me (was bought used) Zoli 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 (and all for a really nice lowball price) -- I'd really like to solve this issue and get the gun working well for predator hunting.

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" (as the Germans call them) has excessive headspace and it might become a "reloads only" project for me so I can adjust the brass to fit the chamber well. (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.)

Thanks!

Old No7

AngZoli primers.jpg

[ollogger]

Not sure but to me it looks like they are to hot for the gun, will they go back in the chamber?
may be punch the primer out if it drags on the primer while locking the gun up, did you measure the case for

for to much stretch?


Brad

[GunnyMack]

Are the fired cases LONG? Has head diameter increased?
To me the issue is not pressure as the outside edge of the primers hasn't flowed. I doubt it's headspace, find a set of headspace gauges and check it. I would look closely at the firing pin , is it damaged? Take the gun apart and compare the firing pins side by side. Normally in O/U guns the top barrel firing pin is a tad longer, could be someone swapped them accidentally.

[Walt]

The first thing I would do is use a candle to smoke the bullets of your factory rounds (or use a magic marker), chamber a round, extract and see if the bullets are being engraved by the rifling. If so, break out your .222 seating die and seat the bullet a tiny bit deeper and try it again. Your chamber may have been cut for a different ogive profile than your factory rounds.

[JRD]

I believe you don’t have a pressure problem but a gun that shows a symptom that can occur in break actions shotguns adapted to rifle cartridges.
You make a good observation on the difference in primer flattening around the edge with Hornady versus Remington factory loads but frankly I don’t think the Hornady is excessive.
The strange firing pin indents I believe are a function of the break action design, not that it’s a break open but that has internal hammers that have enough energy to fire the rifle primer but don’t continue to hold the firing pin firmly forward. Thus after ignition the primer indent is basically pushed back out to flat again and you are having a bit of primer flow into the firing pin aperture that is causing your hard opening.
Shotgun actions usually have large diameter firing pins that are a loose fit in their aperture in the breachface because they only deal with low pressures and primer flow isn’t an issue.
When a rifle cartridge is put in a shotgun actions, they typically will put in smaller diameter firing pins that are in a bushing that’s a much tighter clearance to resist primer flow and lessen the likelihood of a pierced primer.
Actions adapted to rifle cartridges may also have some sort of gas containment built into the firing pin bushing.
That’s why double rifle conversions of a shotgun action can be a bad idea if no provisions are made for primer flow and pierced primers.
In your case you may need to experiment with different loads that give the least primer flow. Unless you want to redesign or remake certain related action parts, your gun may just be that way.

[Old No7]

I appreciate the responses above. 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 agree with JRD that it's a function of the top-break design with the rebounding firing pins which are pulled away from the breech face (as the pins sit roughly 1/16" below the face of the breech after "firing").

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

Thanks JRD and all others!

Old No7

[GunnyMack]

We are all on the same page, it's just the nature of the beast. I'd say any normal load for 222 will be fine.
Back in school I bought a box of parts. Internals, receiver,barrels and wood. Nothing was fit. I proceeded to put together a 12ga o/u that is affectionately known as The Redheaded Stepchild. I always suspected it is a Zoli. Seeing your pictures confirms my suspicion.

[earlmck]

I think JRD has it nailed.

And Remington primers will likely be your best bet for a primer that won't be so apt to flow back into the firing-pin hole -- they are the hardest I know of.