Hammo Posted November 24, 2016 Report Share Posted November 24, 2016 Hi All Just purchased a secondhand single barrel .410, and it has a 70mm chamber. Seems pretty odd, as all the .410 carts are either 2 1/2 or 3 inch. I would imagine the cost of reaming out the chamber to 3 inch, and getting it re-proofed would be more than its worth. But why on earth is it an 'in between' chamber length? Hammo Quote Link to comment Share on other sites More sharing options...
theshootist Posted November 24, 2016 Report Share Posted November 24, 2016 I can't answer why it's 2.75" but I'd agree that reaming to 3" won't gain you much. I'm now sticking the 2.5" in mine. Quote Link to comment Share on other sites More sharing options...
snarepeg Posted November 24, 2016 Report Share Posted November 24, 2016 Never come across a 70 mm in 410. Can you measure it o confirm its not 76 mm. Quote Link to comment Share on other sites More sharing options...
Vince Green Posted November 24, 2016 Report Share Posted November 24, 2016 I suppose its not beyond the realms of possibility that at some time in the past these cartridges were available but have since died out through lack of demand? Quote Link to comment Share on other sites More sharing options...
Uilleachan Posted November 24, 2016 Report Share Posted November 24, 2016 I suppose its not beyond the realms of possibility that at some time in the past these cartridges were available but have since died out through lack of demand? I think thats the case (no pun intended) I've seen a few 2.75" chambered older .410 guns. One solution to avoid the 1/4" chamber gap from the end of a 2.5" cart to the forcing cone, it to cut down once fired 3" carts to suit (and to be on the safe side load with 2.5" recipes working up to a suitable load from there. Third to half (brand dependant) of a sheet of packed bog roll inside a plastic wad ahead of the shot will lift the column a ball park 1/4", for example, exact height would depend on the finished type of crimp used/preferred, if one were to stick with 2.5" loading data). Quote Link to comment Share on other sites More sharing options...
Hammo Posted November 24, 2016 Author Report Share Posted November 24, 2016 Never come across a 70 mm in 410. Can you measure it o confirm its not 76 mm. Hi Measured it and the forcing cone is definitely at 70mm. Just going to have to stick to 2 1/2's. Hammo Quote Link to comment Share on other sites More sharing options...
neutron619 Posted November 24, 2016 Report Share Posted November 24, 2016 CIP says it's a recognised chamber / cartridge length: http://www.cip-bobp.org/homologation/uploads/tdcc/tab-vii/tabviical-en-page12.pdf I wondered if you might have one or other of the two sizes either side of the 70mm as the tolerances would let them almost overlap, but I suspect if it's stamped "410/70", that's probably what it is. Unless you've somehow managed to lay your hands on an actual 36 gauge... Quote Link to comment Share on other sites More sharing options...
snarepeg Posted November 25, 2016 Report Share Posted November 25, 2016 Have a lot of capped 3 inch cases that are actually 73mm. Have the 3 inch final crimp die for the Pacific 266 that is stamped 73 mm. But have never seen a 70mm cartridge on sale. Quote Link to comment Share on other sites More sharing options...
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