Ballistics Problem

[barnesuser28]

I was out shooting prairie dogs with a 6.5x284 and at 414 yards i was having problems with elevation.

Conditions:
Baro: 27.14
Temp: 77*
Humidity: 20%
5* angle shooting up.
sighted in shooting right on at 95 yards in 27.45 Baro, 77*, 0* angle

Using 140 grain Berger VLD at 2839 fps (chronographed in same conditions as sight in).
Shooter called for 5.7 MOA needed only 4.75 MOA

Using a Hawke sidewinder 8-32x56. the only problem that i can find is maybe the clicks on the scope arent exactly 1/4 MOA. But that would mean that the clicks are only .2125 MOA instead of .2618 which is almost exactly 1/4 MOA

 

[Broz]

What rangefinder? PD's can be hard to range are you sure of the distance?

What chronograph? Some will fib to ya.

Other than that I agree the next thing to do is check the scope for proper tracking.

Jeff

 

[barnesuser28]

A Leica 1200 CRF and a Competition Electronics Prochrono digital chronograph. Positive of the distance ranged it 4 times just to make sure and each one was 414-416

 

[Broz]

Best thing to do is to do some actual field testing for drops. Log the conditions and shoot at 300, 500, 700 900 and 1100. Shoot groups and measure drops to center group then log the actual dial up needed for that distance. Later tune the program to match these drops.

I can not say for sure but I am going to guess your actual velocity is off.

If you want to you can change the MV so your dial up for the 414 yard shot says 4.75 moa. Then go shoot again at 600 or 700 and see how it does.

One thing I will recommend is that you keep a log of each shot. Log field conditions, angle and dial up needed to be on. Once you have enough logged data you can then fine tune the program to be correct.

Jeff

 

[barnesuser28]

i used the feature on shooter that allows you to enter the range and the elevation needed and it will give you a new mv and it was 2979. the load was 52 grains of H4831sc i didnt load these so i dont know where pressure signs showed up at in powder charge.

 

[Broz]

Just a quick look at the Hodgdens web site loading data shows that charge to be a few grains over max for the 140's they list. Also that velocity is high too.

If it were me I would be shooting some more drops and gathering actual drop data.

Also a scope tracking check could be in order.

Jeff

 

[barnesuser28]

we will be going out to that same prairie dog town tomorrow so ill try some shots at about 600-700 yards and see what i come up with. if all else fails i will check tracking.

 

[Broz]

I would take a portable target to gather drop info. A dust ball off a mound or even a hit on a dog can give you less than accurate info. At 600 yards 1 moa is 6" and a hit could still be 1/2 to 1 moa low or high on a standing dog.

Jeff

 

[barnesuser28]

we will be shooting the 338 Lapua for drops so we can just do them both at the same time.

 

[Broz]

Yep, the hole size will be noticeably different..gun)

Jeff

 

[barnesuser28]

haha yep!

 

[woodnut]

Don't know where you're from; but when I went from Va. to S.D. I encountered the same thing. Zeroed at 300 in Va. but shot over a lot of em til I figured to "hold low, they's ridin shetlands! "

 

[barnesuser28]

Don't know where you're from; but when I went from Va. to S.D. I encountered the same thing. Zeroed at 300 in Va. but shot over a lot of em til I figured to "hold low, they's ridin shetlands! "

Did you adjust for the barometric pressure change? That will really screw you up!

 

[woodnut]

Actually, that's exactly what we figured it was. One other interesting tidbit; while the winds blew almost constantly, holding for it proved to be less a hassle than the elevation! Not scientific, but that's the impressions we had. It sure was fuuun !