I was going to throw this target away but it is keeping me awake at night.
I shot 6 shots with a new COAL of 3.51" using 190 smk's loaded with 64gr of IMR 7828 SSC and magnum primers. Previously I had shot the same load with a COAL of 3.44 and they grouped pretty good, generally under .75MOA with a number under .5MOA. I realize they are very lightly loaded but they seem to group better at this speed, at least have in the past.
Looking at the target though, you will see the problem and I can't figure out it.
The shot order was 1,2 in the lower group, followed by 3 in the upper, then 4 in the lower and 5,6 in the upper. The strange thing, and the reason I think it is the load, is from the chrono data below:
Shot, fps
1, 2544
2, 2559
3, 2645
4, 2569
5, 2614
6, 2635
You'll note shots 1,2,4 that make-up the lower group average 2,557fps and shots 3,5,6 average 2,631 a difference of 75 fps. I don't think 75 fps is enough to cause a 2" difference at 100yds by itself, what, maybe 1/4"? This gun is more load sensitive than other's I have known and has produced some really nice groups below .5MOA with the best being .221MOA. The groups above are .311 and .367 MOA taken individually.
As to the load, I am using twice fired brass, cut and measured on a lathe. It was a new box of 190 SMK and they were seated nearly perfectly at a COAL of 3.51 but measured to the ogive +/- < .001. The powder was measured on a beam and I checked it against a digital when I started. The primers are known to be good.
The only thing I can think of is I wasn't timing the shots that well but all 6 were taken within 20 minutes and the barrel was hardly warm. But the chrono data must be telling something.
The rifle is a Remington tactical long range, 26" barrel in a B&C stock with aluminum bed. I scrape-bedded the aluminum and then bedded it again with JB weld. Everything is torqued and checked with two wrenches (wish that was wenches). Jewell trigger added as well. Shot from a bench on bags.
If it's me, then there are two of me alternating shots. It takes a lot of concentration to get a good group from this gun. I don't have a brake on it and though I am a pretty big person, it still pushes me and the bags back about a foot.
So the final question is, should I ignore the chrono data and assume there is something loose? Any other thoughts on the load? Buy the way, at 3.51 I am .030 off the lands.
Thanks
Jerry
I shot 6 shots with a new COAL of 3.51" using 190 smk's loaded with 64gr of IMR 7828 SSC and magnum primers. Previously I had shot the same load with a COAL of 3.44 and they grouped pretty good, generally under .75MOA with a number under .5MOA. I realize they are very lightly loaded but they seem to group better at this speed, at least have in the past.
Looking at the target though, you will see the problem and I can't figure out it.
The shot order was 1,2 in the lower group, followed by 3 in the upper, then 4 in the lower and 5,6 in the upper. The strange thing, and the reason I think it is the load, is from the chrono data below:
Shot, fps
1, 2544
2, 2559
3, 2645
4, 2569
5, 2614
6, 2635
You'll note shots 1,2,4 that make-up the lower group average 2,557fps and shots 3,5,6 average 2,631 a difference of 75 fps. I don't think 75 fps is enough to cause a 2" difference at 100yds by itself, what, maybe 1/4"? This gun is more load sensitive than other's I have known and has produced some really nice groups below .5MOA with the best being .221MOA. The groups above are .311 and .367 MOA taken individually.
As to the load, I am using twice fired brass, cut and measured on a lathe. It was a new box of 190 SMK and they were seated nearly perfectly at a COAL of 3.51 but measured to the ogive +/- < .001. The powder was measured on a beam and I checked it against a digital when I started. The primers are known to be good.
The only thing I can think of is I wasn't timing the shots that well but all 6 were taken within 20 minutes and the barrel was hardly warm. But the chrono data must be telling something.
The rifle is a Remington tactical long range, 26" barrel in a B&C stock with aluminum bed. I scrape-bedded the aluminum and then bedded it again with JB weld. Everything is torqued and checked with two wrenches (wish that was wenches). Jewell trigger added as well. Shot from a bench on bags.
If it's me, then there are two of me alternating shots. It takes a lot of concentration to get a good group from this gun. I don't have a brake on it and though I am a pretty big person, it still pushes me and the bags back about a foot.
So the final question is, should I ignore the chrono data and assume there is something loose? Any other thoughts on the load? Buy the way, at 3.51 I am .030 off the lands.
Thanks
Jerry
