Originally Posted By: rabbit
Does anyone know if either the Hartin ........... crimp would generally be associated with a higher pressure yield than would the industry standard fold crimp, given same payload and charge?

jack


Jack,

I have a bit of information bearing on this. I have long used the hartin crimp on 65 mm hulls (made by cutting down 70 mm hulls) and also under the star crimps of 70 mm hulls to give better (non dished in) crimps. The latter usage is generally with lightened loads that do not fill the case enough for non-dished star crimps. With these lightened loads in 70 mm hulls, I use 12 gauge overshot card wads in 12 gauge and 16 gauge overshot card wads in 16 gauge. "Normal" hartin crimp practice seems to be to use overcard wads one or two gauge size smaller (16 or 20 in 12 gauge, etc.).

With the addition of same gauge overshot card wad under normal star crimps I seem to consistantly get more complete burning of the powder and seem to get this same more complete burning if the hulls have been shortened. This seems as it should be because any strengthing of this "compound" crimp would logically occur along the hull walls. With sub gauge sized overshot card wads this same strengthening would not be expected.

I do have one chamber pressure datum and it does indicate that use of same-gauge sized overshot card wads does increase chamber pressure at least a few hundred psi, maybe even a thousand psi. However, there is not the degree of control on this result that I would like.

Niklas