Rifle Scopes Think this could be my scope?

[Precisions]

first post! I've been around for a while but never actually created a username. Everything I've learned for shooting and reloading, has been learned rite off this site, so thank you. anyway, tested some hand loads today at 200 and 300 Yards. First after zeroing at 100, I shot at 200 without dialing up to see how much drop I had which was 4.5in. I dialed up 2.25 MOA, and was still low. I had to dial up 3 MOA to hit center of 200, and then 5 to hit center at 300... I came home and tried plugging some of this in to JBM with puzzling results.

I cant seem to get the drop that I actually made, to work with each other at 200 or 300 Yards.
Maybe some calibration malfunction at the factory, or JBM?

 

[Precisions]

Re: Think this could be my scope?

Forgot to add, I'm shooting a .308, with a ss 10x scope. These were 175gr SMK's, 44.5gr Varget, CCI BR2, Lapua brass

 

[Longshot38]

Re: Think this could be my scope?

I don't know what data you used and where you got it. But the world of ballistics is a numbers game full of variables. Everything in ones environment effects the path of the bullet and most things are linked. For example rate of drop for bullets is a constant but velocity has a direct effect on that equation. In addition ballistic coeffient is not a static number, rather it is a dynamic number that is the sum of a complex equation that takes into account things like velocity, humidity, altitude, temperature, and barometric pressure. And many time when we compute these manually we will find variations in these numbers from the published ones for the vary reason I listed previously.

 

[42769vette]

Re: Think this could be my scope?

the ballistics chart is irrelevant here. you were 2.25moa low, you dialed up 2.25 moa and were still low.

overall you dialed 5.25 moa up to get your poi to move 2.25 moa. it sounds like a scope issue to me

 

[Rick 324]

Re: Think this could be my scope?

As Longshot38 mentioned above there are too many variables that could change to make your program read wrong. One of your issues may be that your scope is not adjusting properly (as 42769vette mentioned). Are you inputting the bullet drop into JBM? or are you inputting your actual ballistics, weather conditions, elevation?

Did you dial up to 3 MOA total to get to the center at 200 yds? or did you dial 5.25 MOA to get to center at 200? If you dialed up to 5.25 then either your zero was off or your scope is not tracking correctly.

Also you did not mention your barrel length! This will have an effect on your overall Muzzle Velocity. I get 2650 fps shooting the 175 SMK out of my Savage 10 with a 24" barrel and my adjustment from 100 to 200 yards is .5 Mills (3.6")!

There are too many different things that may be going wrong in the equation. The last thing that I always do before leaving the range is go back to my Zero Range (100, 200) and fire my rifle to make certain that nothing wierd happened.

Problems suck, but work at 1 variable at a time until you find the one that is off and then you will be back in action!!!

Good Luck!!!

 

[Hook Creek]

Re: Think this could be my scope?

seems like a scope problem to me

 

[Precisions]

Re: Think this could be my scope?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 42769vette</div><div class="ubbcode-body">the ballistics chart is irrelevant here. you were 2.25moa low, you dialed up 2.25 moa and were still low.

overall you dialed 5.25 moa up to get your poi to move 2.25 moa. it sounds like a scope issue to me </div></div>
Sorry I should have said it better, but it was 3 MOA in total to start hitting center at 200. But I just thought it was a weird differential between what I dialed from 200 to 300, and what JBM said from 200 to 300. I'm really only using JBM so I can get an idea on my velocity's. So if you look at the drop in the pic, it says at 200 yards, There is a drop of 4.6in, which is what I had. But my scope adjustments and what it says on JBM dont match up. It does at 300 Yards, but not 200? just seems weird to me.

 

[Precisions]

Re: Think this could be my scope?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rick 324</div><div class="ubbcode-body">As Longshot38 mentioned above there are too many variables that could change to make your program read wrong. One of your issues may be that your scope is not adjusting properly (as 42769vette mentioned). Are you inputting the bullet drop into JBM? or are you inputting your actual ballistics, weather conditions, elevation?

Did you dial up to 3 MOA total to get to the center at 200 yds? or did you dial 5.25 MOA to get to center at 200? If you dialed up to 5.25 then either your zero was off or your scope is not tracking correctly.

Also you did not mention your barrel length! This will have an effect on your overall Muzzle Velocity. I get 2650 fps shooting the 175 SMK out of my Savage 10 with a 24" barrel and my adjustment from 100 to 200 yards is .5 Mills (3.6")!

There are too many different things that may be going wrong in the equation. The last thing that I always do before leaving the range is go back to my Zero Range (100, 200) and fire my rifle to make certain that nothing wierd happened.

Problems suck, but work at 1 variable at a time until you find the one that is off and then you will be back in action!!!

Good Luck!!! </div></div>
When I use JBM I just put what bullet I'm using fter choosing from a list, then I start trying to guess what velocity I think it might be, untill I get the amount of drop I had at the range that I tested it at. Thought it was a pretty slick idea being that I have no Chrono lol. the velocity that I came up with is 2570 using this meathod out of a 20in barrel. No matter what JBM says, I stick with my own data. I only use it to give me a general idea of some things.

 

[jbmillard]

Re: Think this could be my scope?

It's very hard to diagnose potential problems when looking at the output.

Do you have "Elevation correction for zero range checked"? What did you use as inputs?

If you still have a problem, use the report bug button on the output; or post the inputs you use and I can help you find the problem.

Brad

 

[Precisions]

Re: Think this could be my scope?

 

[jbmillard]

Re: Think this could be my scope?

Your Elevation angle looks a little large, but not necessarily unreasonable. The moa required for 300 yards also seems excessive.

Velocity also looks reasonable. How are you measuring the MOA? What scope are you using (did I miss it in your post)?

Also, using drop is a horrible way to get an idea of velocities. It's not accurate.

 

[EXTREMEPREJUDICE]

Re: Think this could be my scope?

You really don't have a good baseline to begin with so all the outputs from your data are suspect. I doubt that is your correct muzzle velocity........my guess is lower, especially based on your recipe and using a 20" barrel. While you can approximate your MV using the technique you profess, you have to take samples at longer distances to derive accurate results. You are only comparing drop relative to 100 to 300 yards. You also indicate in your inputs no wind value, zero?? It could be you were testing on a completely calm day but...
Finally, it's obvious as mentioned that your scope has some issue as it is not relating POI relative to POA/elevation change. Test your scope and chronograph your load then start looking at the results using JBM. Just my observations, YMMV.

 

[Temp9]

Re: Think this could be my scope?

How are you measuring range? Often times, distance markings at ranges are off by considerable amounts. A laser rangefinder is a much better bet for getting accurate results.

 

[Doeboy]

Re: Think this could be my scope?

I would go out and just shoot the dam thing and make my own calculations like every one say, way too (many variances). Kinda like Females!

 

[Precisions]

Re: Think this could be my scope?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EXTREMEPREJUDICE</div><div class="ubbcode-body">You really don't have a good baseline to begin with so all the outputs from your data are suspect. I doubt that is your correct muzzle velocity........my guess is lower, especially based on your recipe and using a 20" barrel. While you can approximate your MV using the technique you profess, you have to take samples at longer distances to derive accurate results. You are only comparing drop relative to 100 to 300 yards. You also indicate in your inputs no wind value, zero?? It could be you were testing on a completely calm day but...
Finally, it's obvious as mentioned that your scope has some issue as it is not relating POI relative to POA/elevation change. Test your scope and chronograph your load then start looking at the results using JBM. Just my observations, YMMV. </div></div>
Remember its just for a general idea. I'm not expecting to be exactly on point with anything. With that being said the difference is still pretty off. I like to do this so when I go to take some shots at longer distances, I have something to start off with so im not completely off target. I have to work with what I got, and in this case I have no Chrono. The velocity specified didn't seem high to me being that I'm a pinch before compression with that amount of powder, and .5 before what's supposed to be the max. I thought it seemed reasonable.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Temp9</div><div class="ubbcode-body">How are you measuring range? Often times, distance markings at ranges are off by considerable amounts. A laser rangefinder is a much better bet for getting accurate results.
</div></div>
I use a range finder. Since I started using one I have also noticed that shooting ranges can be pretty off.

 

[Rick 324]

Re: Think this could be my scope?

Precisions,

If you went back after shooting and you were able to dial your zero right back to your origional dope then you are finding that your actual adjustment for 200 yards is 3 MOA and 8 MOA (From 100 yd zero to 300yards) for 300. This data is more valuable than relying on JBM to try to tell you what it should be. You actual rifle DOPE is what you need, not what JBM tells you.

Keep shoting and learning your own rifle and make up your range cards based on that. Any long time shooter will tell you that JBM will get you close, but you still have to go out and do the work.

Good Luck!!!

 

[jbell]

Re: Think this could be my scope?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JBM</div><div class="ubbcode-body">
Also, using drop is a horrible way to get an idea of velocities. It's not accurate. </div></div>

BINGO