Range Report 6.5 Creedmoor Question

[Rick 324]

Hello everyone,

I got some intereting results at the range today and I wanted to see if anyone has ever had results like this. I am doing load testing and I am shooting my Savage 10T-SR (24" barrel) supressed. With the 147 ELD-M bullet, 41.5 gr. H4350 @ 3.149" OAL. I had a good group at 100 yards (wpild have been great but I jerked one shot out) and then a great group with the same load at 200 yards (.911" ctc for 5 shots).

The odd part was that my 200 yard group only dropped .5" low of my 100 yard group. This is great for ballistics, but all of my calculators are saying it shiuld have been about 1.5" low. Now I am not sure og the reliability of the calculators.

has anyone else seen this happen? If so, did the ballistics calculators work for the other ranges tried?

any info would be greatly appreciated!

Semper Fi!
Rick

 

[Rick 324]

Sorry I forgot to ads 2700 fps, 6480' elevation and 50 deg. Temp...

 

[davsco]

could it be your measurement of scope centerline over bore centerline is off a little? maybe not thinking correctly this late in the day...

 

[Rick 324]

How would the scope height have that big of an affect on the impact? I am asking because maybe I don't fully understand the effect. Please help...

 

[grinnergetter]

I'm running 140's at a much lower elevation but I have .4 mil drop from 100-200. I really had to take the time to get the best possible entries into my calculator. Garbage in = garbage out.


If everything is right...stretch it out further and see what happens at 300+

 

[jg6.5]

I’m not trying to sound like a smartass asking this, but is your 2700 FPS verified over a chrono? If it’s an estimate based off of a reloading manual, you could be shooting faster than 2700 FPS. Other than that, if everything else is dead nuts on for input (scope height, elevation, etc), then I agree with stretching out further to see how it compares. I have a hunch that there’s an input problem though.

 

[Rick 324]

Hi jg6.5,

I verified the speed over a chrono at the same time I shot the groups. I completely understand that without an accurate chrono reading the data is more or less useless.

I will definitely need to stretch it out soon, but just wanted to find out if others have had a same experience.

Thanks,
Rick

 

[tna9001]

How would the scope height have that big of an affect on the impact? I am asking because maybe I don't fully understand the effect. Please help...

Hello Rick,

The effect is simply, the axis of the scope not being on the same plane as the axis of the barrel. A solver will compensate for this difference, that is why it is important to measure the height of the axis of the scope above the axis of the barrel accurately.

I ran your numbers through my solver changing only the sight height. Using 2.75" (how my rifle is set up) I get .34 mils at 200 yards, using 1.5" I get .51 mils, this translates to a 1.2" difference at 200 yards. Those numbers demonstrate why it's important to set the correct sight height correctly in your solver but doesn't explain what your seeing. You'd have to be pushing that 147gr ELD at 10,500 fps to only have a .5" drop between 100 and 200 yards, that's a hot load!!!

 

[Rick 324]

Hi tna9001,

That is why I am asking for help. The actual velocity I am seeing is definitely not 10,500 fps. But the ballistics are confusing me. When I input my scope height in my calculator I used 2", but I will go back and re-measure that today.

Thanks for all the input.

Rick

 

[tna9001]

I wish I could be more helpful, I'm sure someone will be along with the answer.

 

[Hardpan]

I just had a issue with my ballistic calculators yesterday as well. Scope has a 2.66in height. Calculator says 8.01 mils for 1000 yards. Previous load data had scope height at 1.5in which gave a elevation of 8.3 mils for the same round. Yesterday 8.0 mils wouldn’t come close to the target. Weather was taken with a weather flow wind meter and factored in to the calculations. Checked my previous dope and needed 8.4 mils to hit 1000. Seemed like 1.5 in scope height in the calculator was actually how my rifle was shooting and not 2.66. Same result at 500 also. I think I’m just going to really use and go off my data book rather than rely on a calculator.

 

[BIRDHUNTER]

Try this, set up a target at 25 yards with a small dot (or the shortest distance your scope will focus down to parlax free), pull up your dope for the distance, fire a shot, measure the distance off and adj your scope height number in your device until it matches the short distance shot. Once POI and POA are the same at the short distance then check your dope using the new scope height number at 200, 300, etc.