Need a reality check, JBM and a Service Rifle

[itwillis]

Hoping someone here can help me out and point me in the right direction. I have a new service rifle for CMP (AR15). The first match this year will be a prone match 600 yards only (mid-range). I do not have access to confirm a 600 yd zero before the match so I want to zero for a trajectory that will put me on the board without too much trouble.

I ran JBM on two sets of parameters. Both sets I used the Litz BC for the Sierra 80gr Matchking, a sight height of 2.6", and a zero range of 600 yards to see how high I should be over the POA at 100 yards.

Now here is where I need some help, one set of numbers I set the zero offset at 18" high at the zero range (600) because I use a six o'clock hold and 18 inches from the bottom of the bull would put me in the middle of the x-ring (theoretically) and it said I needed to have a trajectory 18.0" high at 100 yards.

The other set of numbers I put it in with 0" offset at the zero range (600) and it said the trajectory would be 15.0" high at 100 yards.

Assuming I hold a perfect sight picture with a 6 o'clock hold, which scenario would be correct? Or am I way off?

 

[Erud]

Hoping someone here can help me out and point me in the right direction. I have a new service rifle for CMP (AR15). The first match this year will be a prone match 600 yards only (mid-range). I do not have access to confirm a 600 yd zero before the match so I want to zero for a trajectory that will put me on the board without too much trouble.

I ran JBM on two sets of parameters. Both sets I used the Litz BC for the Sierra 80gr Matchking, a sight height of 2.6", and a zero range of 600 yards to see how high I should be over the POA at 100 yards.

Now here is where I need some help, one set of numbers I set the zero offset at 18" high at the zero range (600) because I use a six o'clock hold and 18 inches from the bottom of the bull would put me in the middle of the x-ring (theoretically) and it said I needed to have a trajectory 18.0" high at 100 yards.

The other set of numbers I put it in with 0" offset at the zero range (600) and it said the trajectory would be 15.0" high at 100 yards.

Assuming I hold a perfect sight picture with a 6 o'clock hold, which scenario would be correct? Or am I way off?

I don't know, but you are way over-thinking this. Just come up 12 minutes from your 100 yard zero and you will be in the black, should be close-ish to the middle. Use your sighters to dial it in and WRITE IT DOWN for next time. The 600 yard black is 6 MOA from edge to edge, so 3 MOA from the edge to the center. Thinking about it in inches will just give you a headache.

Good luck,
Erik

 

[Douglas-001]

I actually am up 12.5 minutes from a 200 yd. zero. I will assume you are using 80 GRN SMK touching the lands with a Rem 7 1/2 SRP and RL-15 @ 24ish grains? Like ERUD said, write everything down. time of day, wind speed and direction, sunlight, firing point, relay #, recipe on the ammo, the color of your socks, what you had to eat before slinging up. As soon as you finish your string(s), write it all down in your log book or whatever you are using. DO NOT WAIT to get home and write it down. I am confident in my elevation zeroes when I shoot, but when it comes to wind, I would rather put too much wind on the gun as opposed to playing catch up during the string. You may try the same thing for your elevation. Good luck and good shooting!

Doug

 

[Sterling Shooter]

Shoot the MR-31 target at one hundred yards with your six o'clock hold and adjust for 18 inch high impact from one hundred yard zero and that will translate to x ring at 600 yard target using a 6 o'clock hold.

 

[itwillis]

Shoot the MR-31 target at one hundred yards with your six o'clock hold and adjust for 18 inch high impact from one hundred yard zero and that will translate to x ring at 600 yard target using a 6 o'clock hold.

That is exactly what I needed thanks.