My Merkel 16 bore O/U shotgun was proofed in 1933 and has 65 mm chambers and is in excellent condition. Question what would be the maximum service pressure for shot shells that I would load/fire in this Merkel? I have not seen or missed German shot shell max service pressures listed based on gauge and chamber length.

Is this information accurate? "From Larry Brown's recent communication with the Birmingham Proof House, I thought an addendum should be placed at the end of this thread in case anyone is saving it for future reference:

**650 bars is standard CIP (British and European) service pressure for shells designed for guns proofed at the CIP standard of 850 bars**

European (CIP) proof pressure of 850 kg per sq. cm. (BAR) = 13,920 psi proof pressure= 10,730 psi service pressure (SAAMI)

Per the 1954 Rules of Proof, here are the equivalent service pressure values:
3 tons--8,938 psi
3 1/4 tons--9,682 psi
3 1/2 tons--10,427 psi
4 tons--11,917 psi
These numbers SHOULD apply to guns proved under the 1925 rules, which were stamped only with chamber length and shot charge. Thus, a 2 1/2" chambered gun, 1925 rules of proof, would be equivalent to 3 tons; a 2 3/4" chambered gun to 3 1/4 tons.

A service pressure of 3 tons per sq. in. = 8,938 psi service pressure (SAAMI)"

Thanks!
Jim

I for one would not mix British & German data unless you know you are comparing apples to apples. Per Wirnsberger, the chamber of a German double under the 1912 rules pushing OVER 55.5 grains, 1 1/4 oz, of shot for a 12 bore with 70mm chambers or OVER a 1 oz payload in a 16 bore should not be chambered unless the scattergun has experienced special proof which is in excess of 75% over the service load.

Cheers,

Raimey
rse

The 1989 version of Wiederladen, shows in the table for shotgun ammunition, that the maximum allowable gas pressure for 16 ga shells( this is service load, not proof, pressure) is 680 bar. Current rules may use different units of measure.
Mike

Good info there Ford. I am curious to what psi value this 680 bar actually transforms?

Cheers,

Raimey
rse

Raimey, IF the internet converter is to be believed, 680 bar converts to 9,860 psi.

Remington 16 gauge Game Loads, 2 1/2 drams equivalent, 1 ounce, #6 or #8, five bucks a box on sale. Won't blow up any gun and won't send you to the poorhouse.

Mike,
Does it list the maximum allowable service pressure for 65 mm 16 ga. shells?
Thanks for the previous information!
Jim

Jim,
As far as I can tell, the max is the same for 65 and 70mm.
Mike

Mike,
Thanks for the information!
Jim

Jim,
You are welcome.
Mike