doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Sterlingworth pin gun 12 ga.

What length shells can I shoot? Can see some indication of forcing cones, but can't feel them with a machinist rule. A fired Federal paper trap shell goes in all the way, without squeezing the mouth, at all. Thanks for any help.....Grant.

Sounds like the gun in question may have had its chambers lengthened. The Sterlingworth pin guns, all 12-gauges, left North 18th Street & Windrim Avenue with 2 5/8 inch chambers intended for 2 3/4 inch shells.

I have several of them and shoot 2 3/4 shells in them. I don't just shoot low pressure, but regular Lead, Bismuth and Steel (in the open choked one), and have had no problems...Geo

Researcher: I'm confused as to why they would be chambered at
2 5/8" if intended for 2 3/4" shells. I have used standard shells in the shorter chambers but have always used low pressure loads when I do. Gil

Realize that a fold/pie crimp 2 3/4" shell will have a"Loaded" length of about 2 3/8". The 2 3/4" is the fired length with the crimp open. You will not feel any resistance when loading the shell even in a 2�" chamber, much less a 2 5/8" one.

A roll crimp shell will not shorten much over 1/8" when crimped so chamber length is much more critical on them. "Never" fire shells which are actually pushed into the cone in their loaded condition.

A pie crimped 2 3/4" shell should probably not be fired in a 2 5/8" chamber having a cone length of less than about 3/8" nor in a 2� chamber with a cone length of less than about �".

DO NOT shoot shells longer than the chamber if it has a very abrupt cone or a step where the end of the hull actually opens out into the bore itself.

Gil, Parker also cut chambers 2 5/8� and recommended 2 3/4� ammunition. They wanted the hull to open into the forcing cone thinking it would result in a better gas seal,as the fiber wads transitioned to the bore. They were probably correct.

I draw the line where the open shell length exceeds the chamber by more than 1/8". IOW, I'd not use 2 3/4" star crimped shells in a 2 1/2" chambered 20 gauge.

Another consideration is the actual length of the fired hull. Many brands that are labeled 2 3/4" are not that long when opened. Line some up side by side sometime and look at the difference. If one is worried about that 1/8", I believe it would not be a big job to find some loads that actually opened up to about that length.

SRH

Thanks for the advice....Grant

Until fairly recent times SAAMI specs for a chamber to be used with 2 3/4" 12 gauge shells called for a minimum length of less than 2 5/8". I am going on memory here but I seek to recall 2.618" with a maximum angle to the cone of 5� from bore axis. This would give a cone length to nominal chamber & bore dimensions of .400". This shorter length was not listed for any gauge other than 12 for some reason. Current listings do not show this shorter chamber, but a statement is made that chambers were formerly listed with shorter lengths & these chambers were still considered acceptable for use. A shell which opened to the full 2 3/4" length would be reduced at the mouth by 023" when fired in this minimum chamber.

Current minimum chamber diameter at the junction with cone is listed @ 12g = .798"; 16g = .732" & 20g = .685". Turn a plug to0 about .020" to no more than .025" under that chamber dimension for the gauge at hand & if it will enter to a depth of 2 3/4" don't fret the chamber. Be "Absolutely Certain" the load fired is compatible for use in the gun in question.

In a 2 5/8" chambered 12 gauge I would much prefer to fire a 1 1/8 oz load @ 1150 fps in a 2 3/4" shell than a 1 � oz load @ 1330 fps in a 2 5/8" shell.
The total ballistics of the load are of far greater importance than actual chamber length as Long as there is clearance at the end of the shell for the crimp to open unretarded.