Why and how come

[Tnwhip]

I have a 220 Swift. My load with 55sp runs 3570fps using a Magneto Speed. I have had this rifle for a long time and have only shot it out to 300 yards. My zero is 200 yds,So I Never worred about turning knobs. I now have a 500y. range. I wanted to see what she would do. I shot at 200,300,400, and my last target is at 512 yards. I turned the knob till I put 3 shot in the bull and wrote it down. When I got home and put all my info in the calculator. It was way off. I had to juggle things around to get my drop chart to come out right. Had to bring the velocity down to 3100fps and the bullet coefficent from .235 to .200. to get it close. Could it be my scope Knobs are off. It is an old, Made in Japan Tasco 6x24 mil dot varmint scope. I have got if figured out but the balistic calculator is saying this
300 yd 1.9 moa I hit the bull with 3 moa
400 yd 4.4 moa 6 moa
500 yd 7.6 moa 11 moa
That is a big difference. I guess I should shoot a box target and that will let me know how close it really is.

 

[WildRose]

I have a 220 Swift. My load with 55sp runs 3570fps using a Magneto Speed. I have had this rifle for a long time and have only shot it out to 300 yards. My zero is 200 yds,So I Never worred about turning knobs. I now have a 500y. range. I wanted to see what she would do. I shot at 200,300,400, and my last target is at 512 yards. I turned the knob till I put 3 shot in the bull and wrote it down. When I got home and put all my info in the calculator. It was way off. I had to juggle things around to get my drop chart to come out right. Had to bring the velocity down to 3100fps and the bullet coefficent from .235 to .200. to get it close. Could it be my scope Knobs are off. It is an old, Made in Japan Tasco 6x24 mil dot varmint scope. I have got if figured out but the balistic calculator is saying this
300 yd 1.9 moa I hit the bull with 3 moa
400 yd 4.4 moa 6 moa
500 yd 7.6 moa 11 moa
That is a big difference. I guess I should shoot a box target and that will let me know how close it really is.

If it's an old tasco it's probably graduated in IPHY instead of MOA. That's the first thing I'd check.

Next, if it's an old tasco the clicks are probably not very reliable or consistent.

That's just not a scope built for what you're doing.

 

[Tnwhip]

If it's an old tasco it's probably graduated in IPHY instead of MOA. That's the first thing I'd check.

Next, if it's an old tasco the clicks are probably not very reliable or consistent.

That's just not a scope built for what you're doing.

Yea I know it is an old cheep scope and I hate cheep scopes but It has been on there sense the 90s. It has held up and it is pretty clear for what it is and holds zero. It is a 6x24 and it does have target turrets. . Maybe tomorrow I will run a box test. I have been shooting the rifle off and on sense 1976 and this is the second scope that has been on it. Like I said I have never shot anything over 300 yards with it, till yesterday. It has been a safe queen most of it's life but it is a shooter, I couldn't beleave the group it shot at 500 yds. could have covered them with a snuff can.

 

[Tnwhip]

Yea I know it is an old cheep scope and I hate cheep scopes but It has been on there sense the 90s. It has held up and it is pretty clear for what it is and holds zero. It is a 6x24 and it does have target turrets. . Maybe tomorrow I will run a box test. I have been shooting the rifle off and on sense 1976 and this is the second scope that has been on it. Like I said I have never shot anything over 300 yards with it, till yesterday. It has been a safe queen most of it's life but it is a shooter, I couldn't beleave the group it shot at 500 yds. could have covered them with a snuff can.

And it does say 1/4" 1click

 

[KYpatriot]

It isn't uncommon for the clicks to be off like that. If you have a rifle that you want to shoot at long range there is really no substitute for a quality scope. Holding zero is good, but returning to zero is even tougher and you'll get frustrated quick if your scope is holding you back.

Ammo is just too expensive these days to just chuck rounds out there with a crappy scope- upgrade that thing!
Ahhh, I love spending other people's money I should have been a politician.

 

[Tnwhip]

It isn't uncommon for the clicks to be off like that. If you have a rifle that you want to shoot at long range there is really no substitute for a quality scope. Holding zero is good, but returning to zero is even tougher and you'll get frustrated quick if your scope is holding you back.

Ammo is just too expensive these days to just chuck rounds out there with a crappy scope- upgrade that thing!
Ahhh, I love spending other people's money I should have been a politician.

I have a Weaver varmint scope I can put on her if I have to, I am going to test this Tasco and will let everyone know how it tracks when I can get a calm day. Today was perfect, cloudy and very little wind but had things to do. Maybe tomorrow. I don't expect much from cheep scopes. I want ever by another cheep $100 scope but I have two tasco varmint scopes that I have had for a longgggggggggggg time. On my other rifles I have 2 Burris, 2 Vortex, 2 Weavers and 2 Nikons., and Leupold. The tasco had worked good for what it is just never twisted the turnets that much, We will see how it does or doesn't. I am just messing around with it.

 

[WildRose]

And it does say 1/4" 1click

Then make sure your ballistics calculator is using .25" instead of .25moa graduations and your corrections are in inches instead of MOA.

 

[KYpatriot]

Also, if you do a tall target test and find that the scope is consistent, in other words it returns to zero each time and moves the same amount when you dial you can still use it effectively even if it isn't dialing what you ask. If you find that the error in the clicks is consistent just apply a correction factor.

For example, if you find that eveytime you dial 20in of elevation you really get 23, and it does this every time, then you are good to go. You just divide 20 by 23, giving you a correction factor of 0.869. Again, just take what you dialed and divide it by what it really gave you, and that's the correction factor.

Then, set up your ballistic program with your real velocity and BC just like you would if the scope were perfect. When you go shooting and use the app to calculate your elevation for the shot you take the number it spits out and then correct it with the correction factor. Using the previous example you'd take the correction factor of 0.869 and multiply it by the elevation the app suggests. Some apps even allow you to input a correction factor into the program so it accounts for this scope error automatically.

Remember this only works obviously if the error is repeatable. In many scopes it is, and even some high end scopes will exhibit some of this. The main thing is repeatability.

 

[Tnwhip]

Well the old cheep Tasco is tracking pretty good at least as good as I can shoot. I resighted at 100 yards and went up 1" for 7 shots then Went to 10", then down to 0 then back to 10 and back to 0. It was real close to dead on. I shot targets from 100,200.300.400,and 500. It was a little windy 5mph but real sunny and lots of mariage. To see what the true drops were.
0@100
1.75@200
3.25@300
6.25@400
10.25@500
I put my data back in the calculator at 3100 fps like before and it was off but not as much as before, so I put in my velocity at 3550 and it came out like it is suppose to. I still had to use .2 for the ballistic coeffcient.
Before I was using a 200 yard zero. Now with a 100 yd zero it came out real close. Don't under stand it. Heck I know what the drops are and got the drop chart made up. The picture got turned side ways but You can seen the the picture the old cheep tasco tracks prettygood for a cheep scope.

 

[KYpatriot]

Awesome glad it worked out for you. Old and cheap is better than new and cheap. Like everything else these days, stuff just used to be made a little better than now. Enjoy!