Posted: Thu Aug 18, 2005 5:38 pm
Richard,
I am by no means an expert in interior ballistics and am yet to meet anyone who is but consider this.
Whith a lot of these larger capacity cases (and some smaller ones) barrel life is on the shorter side and we tend to get a lot of erosion when shooting them. When you start out with a fresh chamber and seat your proj. to touch the lands or there abouts you will have an over all case length or seating depth or however you wish to measure it of 'x'. After approx 500 or so rounds you may have to seat your projectile out another 40, 60, 80 thou to make contact with the lands again. not only is this wear in your throat but also a considerable way along the barrel in a tapering effect, therefore the bore size has grown. With this your initial pressure will drop due to less resistance as the bore is now larger. Due to this you now have to increase your powder charge to get your former velocity back. This happens with all barrels, but we see it much quicker in the larger cases. This ofcourse may not be your problem but maybe it is.
With caution increase your powder charge until you get your former velocity back but keep an eye on pressure signs. My guess is that you will add couple of grains to your load and get your old velocity back with no more pressure than you started with.
regards,
Shane
I am by no means an expert in interior ballistics and am yet to meet anyone who is but consider this.
Whith a lot of these larger capacity cases (and some smaller ones) barrel life is on the shorter side and we tend to get a lot of erosion when shooting them. When you start out with a fresh chamber and seat your proj. to touch the lands or there abouts you will have an over all case length or seating depth or however you wish to measure it of 'x'. After approx 500 or so rounds you may have to seat your projectile out another 40, 60, 80 thou to make contact with the lands again. not only is this wear in your throat but also a considerable way along the barrel in a tapering effect, therefore the bore size has grown. With this your initial pressure will drop due to less resistance as the bore is now larger. Due to this you now have to increase your powder charge to get your former velocity back. This happens with all barrels, but we see it much quicker in the larger cases. This ofcourse may not be your problem but maybe it is.
With caution increase your powder charge until you get your former velocity back but keep an eye on pressure signs. My guess is that you will add couple of grains to your load and get your old velocity back with no more pressure than you started with.
regards,
Shane
