I go to knobcreek today with my "newer" (right at 200 rnds) 700 .308. It is the only LR rifle I own. I am shooting HSM 175 grn SMK at 2600fps, per snipercentral's webpage. I dont own a chrono to verify this info so I just trust the manufacturer.
The rifle is factory 700 SPS 26" BBL. Scope NIKON MONARCH 4-16 MILDOT SF. 20 MOA EGW base.
BRIBE
Before I went to the range I printed out three range situations with all known data off of JBM calculations. The only variable was that I changed the BC. They were .475, .496, .505 respectively. Here is the data I put into all three as constants.
60 deg temp
29.92 pressure
humidity 60%
10mph crosswind
G1 drag function
1.25" sight height
460 ft elevation (approx guestimation)
So I double check my sights are tracking. Did a box test (first time I had done this for this setup) and it passed. Then shoot another box at 100 just for the heck of it.
BRIBE
I START MOVING TO LONGER RANGE TARGETS
Things get interesting. The come ups on the JBM calc is high by quite a bit. Hmmm...
I knew I made sure to put select 1/4" clicks on the JBM calculator page (the scope says 1/4" clicks). The only thing I did before I went to the range was to divide the clicks by 4 to get the "MOA" (in my words, "MINUTE OF CLICK") adjustment. I know that MOA equals 1.047 and my scope is 1/4". MOA is MOA, 1/4" is 1/4". Ive learned from you all not to confuse the two especially at long range.
I checked before I went that this "MOC" idea is correct with the amount of clicks. It is. Look below to see what I did.
JBM SAYS:
300yrds = 21.8 clicks / divided by 4 = 5.4 MOC
So I turn it to 5.5 MOC and miss high. I double check my math. Yup, 5.5 MOC is 22 clicks from zero.
BRIBE
It was this way for everything out to 500.
200, 300, 400, 500 was high. If I could have gone further I am positive it would have been high for longer range too.
Look below at what JBM wanted compared to real life shooting:
For 200 JBM wants 9.4 clicks
For 300 it wants 21.8 clicks
For 400 it wants 36.1 clicks
For 500 it wants 52.4 clicks
Here is what real life wants (focus on the clicks and compare to above)
200yds was .75 MOC (3 clicks)
300yds was 4 MOC (16 clicks)
400yds was 5 MOC (20 clicks)
500yds was 11.25 MOC (45 clicks)
WHY THE DIFFERENCE?
BRIBE
I have even gone back to the JBM website and tried to redo it allover again and to no avail. Even a guy at the range had the book "DEAD ON" and his drop charts in that book were even high. I've checked everything I can imagine...
I am to the point that I think the velocity must be higher...but THAT much higher?
Is my math Jacked?
I even did JBM 6 times just now AGAIN before sending this post to make sure I am not crazy. I changed a lot of temperature/ pressure/ humidity settings and it never made that much of a difference. Kept the drag function at G1 and BC at .496.
Help guys...
IN THE BEGGINING
The rifle is factory 700 SPS 26" BBL. Scope NIKON MONARCH 4-16 MILDOT SF. 20 MOA EGW base.
BRIBE
Before I went to the range I printed out three range situations with all known data off of JBM calculations. The only variable was that I changed the BC. They were .475, .496, .505 respectively. Here is the data I put into all three as constants.
60 deg temp
29.92 pressure
humidity 60%
10mph crosswind
G1 drag function
1.25" sight height
460 ft elevation (approx guestimation)
So I double check my sights are tracking. Did a box test (first time I had done this for this setup) and it passed. Then shoot another box at 100 just for the heck of it.
BRIBE
I START MOVING TO LONGER RANGE TARGETS
Things get interesting. The come ups on the JBM calc is high by quite a bit. Hmmm...
I knew I made sure to put select 1/4" clicks on the JBM calculator page (the scope says 1/4" clicks). The only thing I did before I went to the range was to divide the clicks by 4 to get the "MOA" (in my words, "MINUTE OF CLICK") adjustment. I know that MOA equals 1.047 and my scope is 1/4". MOA is MOA, 1/4" is 1/4". Ive learned from you all not to confuse the two especially at long range.
I checked before I went that this "MOC" idea is correct with the amount of clicks. It is. Look below to see what I did.
JBM SAYS:
300yrds = 21.8 clicks / divided by 4 = 5.4 MOC
So I turn it to 5.5 MOC and miss high. I double check my math. Yup, 5.5 MOC is 22 clicks from zero.
BRIBE
It was this way for everything out to 500.
200, 300, 400, 500 was high. If I could have gone further I am positive it would have been high for longer range too.
Look below at what JBM wanted compared to real life shooting:
For 200 JBM wants 9.4 clicks
For 300 it wants 21.8 clicks
For 400 it wants 36.1 clicks
For 500 it wants 52.4 clicks
Here is what real life wants (focus on the clicks and compare to above)
200yds was .75 MOC (3 clicks)
300yds was 4 MOC (16 clicks)
400yds was 5 MOC (20 clicks)
500yds was 11.25 MOC (45 clicks)
WHY THE DIFFERENCE?
BRIBE
I have even gone back to the JBM website and tried to redo it allover again and to no avail. Even a guy at the range had the book "DEAD ON" and his drop charts in that book were even high. I've checked everything I can imagine...
I am to the point that I think the velocity must be higher...but THAT much higher?
Is my math Jacked?
I even did JBM 6 times just now AGAIN before sending this post to make sure I am not crazy. I changed a lot of temperature/ pressure/ humidity settings and it never made that much of a difference. Kept the drag function at G1 and BC at .496.
Help guys...
IN THE BEGGINING