problems

[parker_chp]

I have been trying my hand at some ELR shooting and am running into some issues with how far I'm shooting. I am shooting a 260AI with a 30" barrel running 140 hybrids at 2902 with a SD of 7 ( magneto speed). I have a kestrel 4000 and the AB ballistics app for my phone. my target is a steel plate 42" x 18.5. I have used google earth to range my target ( shooting mtn. to mtn) at 1780 yards. Ive used two scopes ( one mil, one moa) to range it and keep coming closer to 1900 yrds. My shooting elevation is is roughly 2200 ft. and target is at 1900 ft. My AB tells me my dope for 1780 should be up 54.2 moa. I have a set of Barret 15/40 ex rings with a NF 8x32 moar t. I have 61 moa available from my 100yrd zero. I move my rings to the 40 moa position ( adding 25 moa) to try to be in the center of the scope, then dial in the rest. My problem is I'm having to dial in 55 moa plus hold 10 moa in the reticule to hit the target( I've had one hit and recovered several bullets within a few feet of the target). by my math this is 25(rings) +55(turret)+10(reticule)= 90 moa. I don't get it, the dope with the atmospherics for 2000 yrds is only 69.3 moa. Any idea's on where to look for a problem.

 

[pdog2225]

Hi Parker. (this is my best guess at what is happening)
For ELR I also use a 260AI, 8.5T,30" setup using 142smk and a stiff load of RE-22.
I don't know anything about the base you use.

If you are zeroed at 100yds then the following may apply!

So if you have 61MOA of up from your 100yd zero as stated. Then because the scope only has 65moa to begin with (google search) you are up 4.0moa from the bottom. You're still dealing with the adjustment range of the scope. And it looks like your velocity is a little on the low side for shooting that distance. These two things will cause you to use all the scopes moa plus the internal moas.

Been there, done that....pdog2225

 

[Bryan Litz Ballistics]

My suggestion is to get the rifle hitting at ELR, then without adjusting anything but parallax, take it to a tall target at 50 yds (or a really tall target at 100 yds) to verify how many MOA you actually are over your aim point. It seems like your mount isn't actually moving to give you the +25 MOA.

Also make sure you're not mishandling station vs barometric pressure. Use aG7 BC of 0.32 for that bullet.

 

[parker_chp]

Thanks for the replies.

Pdog2225, I'm running 48gr of h4831sc. The reamer I used is set up to run mag length, even though I'm using a long action lol. I really just wanted to run top 260 speeds without any pressure issues or being hard on components. My scope rings are adjustable and preloaded with 15 moa of elevation which can be moved to 40 moa. So in the long run I have a 20 moa base, 15/40 moa in the rings, 65 moa in the scope, and 20 moa in the reticle.

Bryan, I do need to sit down and do a tall target test with this equipment, I have been just assuming is it is all right. I can see being a couple of moa off but to be 30-40 is baffling. Will the difference in pressures really have that much effect?

 

[pdog2225]

Parker
I sent you a PM. pdog2225

 

[jcampbellsmith]

I think you also need to get a much better handle on the horizontal distance to the target. I would engage a surveyor or someone who has the kit to confirm exactly where your firing point and target are so that the effective horizontal range can be calculated to within 10yds. I would input the horizontal range into the app and ignore the 'look angle'.

Until all the data is correct, the calculation results will be mince. Not withstanding the App churning out the correct numbers with correct data, you have said nothing about what you are doing to observe and correct for wind blowing the bullet up or down. I would suspect that every day you go to shoot the wind will do something different to the bullet.

Regards

JCS

 

[bigngreen]

You can use an app called Range Card to get a solid range in the absence of a rangefinder.