Spanish barrel markings.

[jar]

I have an Aramberri "Star Gauge" 20 gauge that was made in 1971 and imported by Interarms. I bought it in 1972 or 1973 and used it for a couple years until moving around the US kinda put all my shooting on the back burner.

Lately I wanted to get back into shooting so got the old shotguns out and gave each a Spa Day. That's when I noticed something that I likely should have research 40 years ago.

Looking at the barrel markings each barrel is marked 15.6 15.8.

The star stamping is * and *** for full/mod.

Why do both barrels show the same 15.6 15.8 stamping if the chokes are really different?

[Jim Watson]

Beats me; 15.6mm is 20 ga bore diameter, the choke constriction would be down from that.
Maybe 15.6 is nominal, 15.8 is measured.

[jar]

One site suggested that the 15.6 was the diameter when the provisional proof was done and the 15.8 was the final bore after finishing.

I really should have been asking all this 40-50 years ago but when you're 20 or 30 you know everything.

[stinkeypete]

I see the question was answered in the dedicated forum for Spanish Shotguns over on Shotgunworld.

Over here, someone can identify an old military rifle from the bolt knob or a revolver from it’s cylinder!

[jar]

Kinda answered.

Of course there are still so many things I should know but seem to have misplaced. Like what is the relationship between the charges used for the provisional proof and the final proof?

Why are the proofing stamps but not the proof charge listed on both the barrels AND on the water table?

[Jim Watson]

Gun Digest ran articles on European proof practice. Twice, actually, once in the 1950s by Baron Engelhart and again in the 1970s by Lee Kennett. Too bad they did not collect them into a book.

When I find my 1971 Gun Digest, I will have information on Spanish proof. There's 1970, and there's 1972 but where is 1971?

[jar]

Well this shotgun is a 1971 with the proofing stamps. Interestingly both the barrel and the water table carry all four Eibar Region proof marks but only the barrel has the proof charge value.

[Jim Watson]

Found the 1971 with article on Spanish proof as of 1970.

"Breechloading shotgun barrels undergo provisional proof in the finished state except for chambering and final polishing at 12000 psi (No doubt a crusher value, now known as LUP.) receiving mark no 21 and the bore diameter stamp in millimeters and tenths.
When resubmitted for definitive proof, bore diameter may not have changed more than 0.4mm or the provisional proof is considered invalid. Definitive black powder proof generates 8800 psi, designated by mark no 24. Definitive bore diameter, chamber length, and barrel weight in grams are stamped. Automatic guns are..."

So your two sets of bore diameters are provisional before polishing and definitive after polishing.

[jar]

Originally Posted by Jim Watson

Found the 1971 with article on Spanish proof as of 1970.

"Breechloading shotgun barrels undergo provisional proof in the finished state except for chambering and final polishing at 12000 psi (No doubt a crusher value, now known as LUP.) receiving mark no 21 and the bore diameter stamp in millimeters and tenths.
When resubmitted for definitive proof, bore diameter may not have changed more than 0.4mm or the provisional proof is considered invalid. Definitive black powder proof generates 8800 psi, designated by mark no 24. Definitive bore diameter, chamber length, and barrel weight in grams are stamped. Automatic guns are..."

So your two sets of bore diameters are provisional before polishing and definitive after polishing.

That's what the good folk at shotgun world suggested.

It's interesting that this shotgun was proofed at 1300kgs which about 18500 psi.

Tried to give it a walkabout but my hips objected strenuously so I went home instead. The Trap & Skeet Club is open again Wednesday afternoon so I'll try again.

Aside and off topic.

Why is the US an outlier having no minimal mandatory proofing standards?