BuffaloBill
Silver $$ Contributor
Hello, I wanted to share results of my first outing with my first build shown in this previous post:
http://forum.accurateshooter.com/index.php?topic=3782587.0
I had read some on-line articles on the optimal charge weight method of finding an accurate load, and had assembled 20 rounds using H4831SC, Hornady 105gr Amax, CCI BR primers, and Lapua brass that I previously fire-formed using a "COW" method. I turned the necks for a clearance of 2-2.5 thousandths and seated the bullets 20 thousandths off the lands.
These are the increments I used:
43.70gr qty 3 vel. 2900
44.65gr 1 2965
45.60gr 1 3019
The above were used for sight-in.
46.55gr 3 ave. vel. 3090
46.88gr 3 ave. vel. 3102
47.22gr 3 ave. vel. 3143
47.55gr 3 ave. vel. 3168
47.88gr 3 ave. vel. 3173
The weekend had arrived and I was determined to shoot this thing even though it was fairly windy (with gusts) here in west central Wisconsin. I have no wind velocity recording equipment but at one point it blew over my cronograph on a camera tripod. The temps were 63F to 75F over the two hours I spent there.
These were the first rounds through this barrel. Is that too early to try and collect this sort of data?
I was hoping for much calmer conditions but just wanted to try it out. I have no wind flags or any experience using them and was having trouble holding on the bull with the wind gusts. I had planned on shooting at 300yds but decided to shoot the 5 test load increments at 200yds. I have horizontal stringing that I hope can be attributed to the wind which was blowing right to left. Note that I hadn't achieved a perfect horizontal zero before using up the first 5 rounds (one would think that looking at the targets that the wind was blowing from the other direction). I am pretty happy with the vertical results of these 3-shot groups though, especially the two hottest loads labeled 7 & 8 (as best I can measure, 0.040" and 0.046"). This is already out-shooting any factory rifles I own.
I tried to locate the center of each test group and compare where it fell with respect to the aiming point, looking for the three test groups that print in a general area. Well, all five groups are roughly in the same location. I didn't use graph paper; that would have been handy. Is that because I shot at 200yds and not farther, like 3 or 4 hundred?
I tried to look for signs of excessive pressure before advancing to the next higher powder increment but did not note anything that I recognized as such. According to Quickload, test load 7 should be around 60KPSI. I photographed the case head & primers under a microscope at work but didn't remember to bring them home with me. They are not as flat as the typical factory ammo I've shot in a 7mm-08.
I tried to measure the increase in case head diameter, measuring just in front of the extractor groove using a standard 1" micrometer. The lightest of the 5 test loads grew about 0.00025", the heaviest grew about 0.0006". I understand that opinions vary on whether or not this can be correlated to pressures?
Being my first build I had been second-guessing a few things I'd done or not done during the chambering, crowning, and bedding, but first indications are pretty decent (for me at least).
What do you think?
Thanks for putting up with the long read......
http://forum.accurateshooter.com/index.php?topic=3782587.0
I had read some on-line articles on the optimal charge weight method of finding an accurate load, and had assembled 20 rounds using H4831SC, Hornady 105gr Amax, CCI BR primers, and Lapua brass that I previously fire-formed using a "COW" method. I turned the necks for a clearance of 2-2.5 thousandths and seated the bullets 20 thousandths off the lands.
These are the increments I used:
43.70gr qty 3 vel. 2900
44.65gr 1 2965
45.60gr 1 3019
The above were used for sight-in.
46.55gr 3 ave. vel. 3090
46.88gr 3 ave. vel. 3102
47.22gr 3 ave. vel. 3143
47.55gr 3 ave. vel. 3168
47.88gr 3 ave. vel. 3173
The weekend had arrived and I was determined to shoot this thing even though it was fairly windy (with gusts) here in west central Wisconsin. I have no wind velocity recording equipment but at one point it blew over my cronograph on a camera tripod. The temps were 63F to 75F over the two hours I spent there.
These were the first rounds through this barrel. Is that too early to try and collect this sort of data?
I was hoping for much calmer conditions but just wanted to try it out. I have no wind flags or any experience using them and was having trouble holding on the bull with the wind gusts. I had planned on shooting at 300yds but decided to shoot the 5 test load increments at 200yds. I have horizontal stringing that I hope can be attributed to the wind which was blowing right to left. Note that I hadn't achieved a perfect horizontal zero before using up the first 5 rounds (one would think that looking at the targets that the wind was blowing from the other direction). I am pretty happy with the vertical results of these 3-shot groups though, especially the two hottest loads labeled 7 & 8 (as best I can measure, 0.040" and 0.046"). This is already out-shooting any factory rifles I own.
I tried to locate the center of each test group and compare where it fell with respect to the aiming point, looking for the three test groups that print in a general area. Well, all five groups are roughly in the same location. I didn't use graph paper; that would have been handy. Is that because I shot at 200yds and not farther, like 3 or 4 hundred?
I tried to look for signs of excessive pressure before advancing to the next higher powder increment but did not note anything that I recognized as such. According to Quickload, test load 7 should be around 60KPSI. I photographed the case head & primers under a microscope at work but didn't remember to bring them home with me. They are not as flat as the typical factory ammo I've shot in a 7mm-08.
I tried to measure the increase in case head diameter, measuring just in front of the extractor groove using a standard 1" micrometer. The lightest of the 5 test loads grew about 0.00025", the heaviest grew about 0.0006". I understand that opinions vary on whether or not this can be correlated to pressures?
Being my first build I had been second-guessing a few things I'd done or not done during the chambering, crowning, and bedding, but first indications are pretty decent (for me at least).
What do you think?
Thanks for putting up with the long read......
