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Scorch · August 31, 2016, 03:37 AM

Model 670 Winchester in 240 Gibbs (like a 6mm-'06 Improved, Very Improved). 240 Gibbs is a '06 case blown out straight, necked to 6mm, but with the shoulder blown forward .050" and a 35 degree shoulder. Designed and marketed by a Canadian gunsmith/wildcatter back in the 1960s. Gain about 100-200 fps over a 6mm-06. Takes an extra 5-6 grains of powder. It is waaay over bore, barrel life is short.

In order to form brass, anneal, neck the case up to 35 caliber, then neck down to 6mm with the Gibbs dies. This will give you a headspacing shoulder at the base of the chamber neck. Fire form with a 60% load, then load as usual.

August 31, 2016, 03:37 AM	#9
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,249	Model 670 Winchester in 240 Gibbs (like a 6mm-'06 Improved, Very Improved). 240 Gibbs is a '06 case blown out straight, necked to 6mm, but with the shoulder blown forward .050" and a 35 degree shoulder. Designed and marketed by a Canadian gunsmith/wildcatter back in the 1960s. Gain about 100-200 fps over a 6mm-06. Takes an extra 5-6 grains of powder. It is waaay over bore, barrel life is short. In order to form brass, anneal, neck the case up to 35 caliber, then neck down to 6mm with the Gibbs dies. This will give you a headspacing shoulder at the base of the chamber neck. Fire form with a 60% load, then load as usual. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services