Impact @ 200 after 100 zero

[kimberyote]

I have developed a load for a 300WSM w/210 berger & 58.5 grains of H4350.
I have very good groups.
After Shooting a group @ 100 yards, with my same aim point, my impact @ 200 was 9" when it should of been 4.7" according to my bulletsflight app.
Am I overlooking something ?
Thx!

 

[ICANHITHIMMAN]

Whats your scope?

 

[Sully2]

I have developed a load for a 300WSM w/210 berger & 58.5 grains of H4350.(Irrevalent)
I have very good groups. (also does not pertain)
After Shooting a group @ 100 yards, with my same aim point, (which is what???) my impact @ 200 was 9" when it should of been 4.7" according to my bulletsflight app.
Am I overlooking something ?

If you are using center bullseye as your aim point I dont wonder at all why you are low at 200. Even with my 22-250 at ungodly speed I have to aim ABOVE the center of the bullseye to get on at 225 yards,,,,and it still just a touch high at 200.

Give full data on the load

 

[bbutturff]

Are you shooting uphill or downhill? It matters.

 

[bbutturff]

Are you shooting uphill or downhill? It matters.

I got it backwards. This would make your point of impact high, not low.

 

[BrentM]

I think what is he is saying is that he did not adjust for 200, he shot it as 100 to figure out drop. Drop was 9" vs 4.7", 4.7 being the expected result.

So, IF I am correct then that means your data is wrong. For example BC, atmospheric conditions etc. My guess is that your velocity is wrong and is likely several hundred fps slower than what you input.

What is relative to the equation I think is what expected velocity did you use, how did you come to that conclusion, and did you chrono the loads?

 

[kimberyote]

Chronyed load. Flat ground. 2550fps.
Changed g7 to g1. No diff. Correct BC used.

 

[BrentM]

Well, hmmmm, that means the round would be 500 fps slower. Not likely, unless you had a messed up powder measurement.

Assuming you shoot well, meaning hold, rifle rest, all of that stuff is good to go, including accurate range to the targets, I would look at your scope mounts and action screws.

Did it group well at 200? How many rounds did you shoot for that 200 group?

BTW- to get a 9.2inch drop that equals 250 yards, with 100 yard zero.

 

[westcliffe01]

So where is your zero point at 100 ? Center of target or X high ? How about showing pictures of both targets so we know where the aiming point and impact points were for both. There are lots and lots of different targets out there, some of which I do not personally understand. My target is a 1" black circle on a white background with horizontal and vertical lines every inch. It is one of the targetZ downloadable targets. You can find it here http://http://www.targetz.com/targetzlib/10058.pdf

If I shoot at 300 I will apply a little black spray paint to enlarge the aiming point so that I can actually see it. There is a target at that website with a 2x2 aiming point but without the scale lines. Often enough I will pin a second target below the first at longer range to verify drop and shoot without adjusting the scope. It is easy to align the grid pattern on the upper and lower targets to make accurate measurement easy.

My measured drop on my 243 AI with 95gr Bergers is 6" from 100-285 yards, which back calculated to 3400fps.

 

[boomtube]

"Am I overlooking something ?" Two things:

You're expecting an "app" to be correct.

You're probably not programing your app correctly for the 100 yard distance you zeroed for.

 

[kimberyote]

Using freezer paper w/red dots.
Old guy here that can't post pics yet.
Velocity was lower than book by 75fps.

 

[westcliffe01]

Did you shoot both 100 and 200 on the same day and at the same temperature ? No up or down slope ? It seems like a lot of drop for that caliber. Ideally once you confirm 100 zero is dialed in 100% then you should shoot the second at the longest distance practical considering wind (within a few minutes of the first group). Shoot at least 5 rounds and better more. You are looking to get the average drop and if the wind is erratic you will be off left and right. Once I get my metal target holders up, then it will be 400 yards for me.