On my gun, I found the NSA 17.5gr 0.2165 slugs to be quite accurate at 900 FPS muzzle velocity. Last night, I shot at the bottom of a half gallon milk jug full of water from 31 meters away to see if I could blow it out. It didn't blow out but it caught the slug inside. Slug velocity on impact would have been about 800 FPS.
I measured the grooves on the slug (which would be the lands in the barrel) to be 0.211" and the lands (groove on the barrel) at 0.216". The slug started out supposedly at 0.2165" but my caliper is not precise to the 10,000th of a inch. This measurement is when I put the slug on the table and put the calipers flat on the table to measure from as low as I can. If I measure closer to the middle of the rifling marks, I get a much bigger measurement of 0.219". I think this maybe because the sides of the slug has started to bow out when it hit the water making the middle part wider than the base. I also think that the starting diameter of the slug is a smidge smaller than the grooves in the barrel. I've measure multiple times and even used a magnifying glass to read the vernier caliper and this is as accurate as I can read it without any specialized measuring instruments.
Having said all that, what do I do with this data. As I said, I find the NSA 17.5gr 0.2165 slugs to be accurate in my gun. But how can I use this data when selecting other slugs in the future?
The hollow point hole went from 2.13mm to 2.82mm as pictured. It's not a mushrooming effect as I think the walls are a bit too thick for the velocities I'm shooting these slugs at. I think it should be ok for penetration at longer distances.
I measured the grooves on the slug (which would be the lands in the barrel) to be 0.211" and the lands (groove on the barrel) at 0.216". The slug started out supposedly at 0.2165" but my caliper is not precise to the 10,000th of a inch. This measurement is when I put the slug on the table and put the calipers flat on the table to measure from as low as I can. If I measure closer to the middle of the rifling marks, I get a much bigger measurement of 0.219". I think this maybe because the sides of the slug has started to bow out when it hit the water making the middle part wider than the base. I also think that the starting diameter of the slug is a smidge smaller than the grooves in the barrel. I've measure multiple times and even used a magnifying glass to read the vernier caliper and this is as accurate as I can read it without any specialized measuring instruments.
Having said all that, what do I do with this data. As I said, I find the NSA 17.5gr 0.2165 slugs to be accurate in my gun. But how can I use this data when selecting other slugs in the future?
The hollow point hole went from 2.13mm to 2.82mm as pictured. It's not a mushrooming effect as I think the walls are a bit too thick for the velocities I'm shooting these slugs at. I think it should be ok for penetration at longer distances.
