Service pressure for Merkel 1939 and1964

[Bill Quillen]

Several of my hunting friends are forced to start reloading due to shortage of commercial shells and have asked me what load is safe to shoot in various old Merkels I have found several good articles explaining the history and complexity of German proof and other markings but none give the actual proof or service pressure used in terms of modern pounds per square inch. Trying to load for sporting clays and early season wild pheasant.
Any help would be appreciated.
Thanks, Bill

[mike ford]

Bill,
Your friends should be able to use the field loads shown in published shotshell loading manuals, with appropriate consideration of chamber length( 65 or 70 mm).
Mike

[Bill Quillen]

Thanks Mike, That was my response ,but I am curious to as to what the actual service and proof pressure was for shotguns proofed in Suhl from 1900 to present. The changes in method and various revisions in marking make it impossible for me as to figure out the actual pressure. Maybe more information than I need to know.

[mike ford]

Bill,
If you want to wrestle through the conversions to Lup and to psia ( if even possible), you might start with charts shown in the article about German Proof Marks, found in the 1975 Gun Digest.
Mike

[Axel E]

Max service pressures shotguns were proofed for in Germany did not change essentially since the 1930s. But knowing them will be of little help to you, as measuring apparatus and protocol differ considerably between European metric (CIP) and American (SAAMI) habits. So a simple conversion from bar to psi or lup by calculation is impossible and may lead to errors from “far too low” to “dangerously excessive”.
These CIP maximum service load pressures, Pmax, depend on gauge:
Up to gauge 20: 830 bar
16 gauge: 780 bar
14 and 12g.: 740 bar
10, 8 and 4 gauge: 1050 bar.
But better grade guns like Gebr. Merkels are usually proofed for the “Magnum” pressure of 1050 bar, regardless of gauge size.

[Bill Quillen]

Thanks Axel and Mike,
Its comforting to know that I am not the only one who could not figure out how to determine this.
A little mystery and a dash of magic will keep us interested.

[Bill Quillen]

Thanks Axel and Mike,
Its comforting to know that I am not the only one who could not figure out how to determine this.
A little mystery and a dash of magic will keep us interested.

[ohiochuck]

Axel,
Please offer an article for the Waidmannsheil concerning the German service pressures for shotguns:
"Max service pressures shotguns were proofed for in Germany did not change essentially since the 1930s. But knowing them will be of little help to you, as measuring apparatus and protocol differ considerably between European metric (CIP) and American (SAAMI) habits. So a simple conversion from bar to psi or lup by calculation is impossible and may lead to errors from “far too low” to “dangerously excessive”.
These CIP maximum service load pressures, Pmax, depend on gauge:
Up to gauge 20: 830 bar
16 gauge: 780 bar
14 and 12g.: 740 bar
10, 8 and 4 gauge: 1050 bar.
But better grade guns like Gebr. Merkels are usually proofed for the “Magnum” pressure of 1050 bar, regardless of gauge size."
Thanks!
Jim