MOA issues

[spudgun]

Ok, a little help here. Trying to get my head around what my scope is telling me in MOA and what a bullet drop programs says.
Here is my data:
6.5 CM
Hornady match 140 gr, BTHP. BC/G1 is .580
Cronographed speed = 2690, Avg FPS
Altitude = 800 ft above sea level
Zero range = 100 yds
Target range = 600 yds
Sight height = 2.0"
Temp = 70
Humid = 70

2 programs tell me that I will need 13.5 MOA to be on target at 600 yds but today after shooting and crony the loads my scope indicated 17.4 MOA to hit target center.

4 MOA at 600 yds is a big difference from what the programs are telling me.

Am I missing something?

Oh one other thing, I have a 20 MOA rail on the gun. I don't think that will effect anything as far a MOA is concerned

 

[rardoin]

Take it back to the 100yd line, dial back to '0.0', shoot a few shots and see if it is still on zero. With that much of a divergence you may have a scope issue

 

[spudgun]

I will do that tomorrow.

 

[Puzzaz01]

Easy way to verify. If you are Still at zero for 600 yds go to a 100 yards place a 2 foot sheet of paper out for a target with a hold point ( bullseye) down at the bottom of the target. Shoot a few shots and you'll see your points of impact will be high, probably 12-13.5" high, measure your distance from aim point to impact. This way you can verify your scopes tracking properly. Works every time and it can be wrong, it's real world.

Darrin

 

[Warren Dean]

What ballistic program are you using?

 

[ballisticdaddy]

You might want to double check that velocity as it seems a bit slow for the Hornady Match 140 grain that I have shot previously

 

[rammac]

Depending on the ballistics program you are using is there a possibility that you are using the path from the line of sight instead of the actual bullet drop (about 83" instead of about 108")?

 

[Mozella]

..... snip............Am I missing something?

Perhaps.

The ballistics program will tell you how much to change your scope from whatever setting puts you on the bulls eye at 100 yards in order to hit the bulls eye at 600 yards. The numbers sound about right.

In fact, if you know nothing about a gun, bullet, or charge weight, if someone shows up to shoot F class you can pretty much count on the difference between 100 and 600 yards to be somewhere between 12 MOA and 14 MOA, or darn close to it. In other words, if a first timer says, "My scope is set for 100 yards. How much should I dial in for my first shot at 600 yards?" Look at his cartridges. If they seem small say 14 MOA. If they seem large, say 12 MOA. If they're large and pointy and the gun makes a big bang, say 11 MOA. Chances are he'll be on paper right out of the box. This won't work for 22LR obviously, but you get the point.

Back to your question. When people say their scope is set at "zero" at 100 yards, that doesn't necessarily mean the turret literally reads zero. Normally, it means they have dialed in some elevation which makes the POA and POI the same at 100 yards.

I'd be willing to bet that when you're hitting the bulls eye at 100 yards, your elevation turret reads 3.9 or so. It that is NOT the case, then you may have a scope problem. You're sure your scope turrets are in MOA as opposed to some other value, right? For example, I have a cheap Chinese scope that is darn good considering the rock bottom price but it took me a while and some head scratching to figure out that the "MOA" turrets really change the POI only about .72 MOA. I printed up custom turret labels and not the scope is good to go. I don't shoot matches with it, but I would if my other competition scopes were not available for some reason.

 

[spudgun]

Maybe I should have included more data for you guys.

Savage 12FV
Vortex PST II 5-25X50 FFP
6.5 CM, 40.5 gr H4350, 140 gr, Hornady Match BTHP
Elev turret on scope set at 0 MOA at 100 yds

Ballistic programs used:

Vortex LRBC
Hornady ballistics calculator

I'm thinking a scope issue. My dope sheets from when I qualified on the 600 yd range were showing a different MOA elevation then they are now. Still using the same reload data and have not changed.

Going back to 100 yds should tell me something about the scope.

 

[spudgun]

Found the issue with the scope.

My zero at 100 yds was off by 3.4 MOA.

All is good now....

Back to the 600 yd range..

Thanks for all your input.

 

[Mozella]

Found the issue with the scope.

My zero at 100 yds was off by 3.4 MOA.

All is good now....

Back to the 600 yd range..

Thanks for all your input.

Well, I was close. I said, "I'd be willing to bet that when you're hitting the bulls eye at 100 yards, your elevation turret reads 3.9 or so."

I'm glad you found the problem, and what's more, it was the best kind of fix; i.e. no further action required. That's WAY better than shipping your scope off to some distant repair shop.

 

[spudgun]

Well, I was close. I said, "I'd be willing to bet that when you're hitting the bulls eye at 100 yards, your elevation turret reads 3.9 or so."

I'm glad you found the problem, and what's more, it was the best kind of fix; i.e. no further action required. That's WAY better than shipping your scope off to some distant repair shop.

Well, I don't ever remember re adjusting the turret after I sighted in at 100 yds. Because I have been shooting only 600 yds.

I knew it had to be something stupid simple because nothing has changed in my loads or gun. I may of not had the set screws tight enough on the top turret.

Luckly, if I ever have a issue with the scope it is only a 30 min drive to Vortex's factory.

Anyway, I am smiling again...

 

[spudgun]

Maybe your rifle didn't read that Ballistic program.
How level is your course of fire?
J

I can't find the USB port on my Savage to plug the program in.

The course spreads over a small valley. the 300, 350, 400, 450 targets are down hill but the rest is level

 

[RDA72927]

I can't find the USB port on my Savage to plug the program in.

Silly, it's under the trigger guard. If you have an older Savage round front-flat back, it will be a RS-232 serial port...

 

[spudgun]

Silly, it's under the trigger guard. If you have an older Savage round front-flat back, it will be a RS-232 serial port...

Would that be a 25 pin or 9 pin serial port?

(you know your showing your age ) and so am I