brand new to optics and pcp's...question

[tommyb]

OP's original question below:

"I zeroed my scope at 25 yds at 6 power, if I change to 13 power (the max) out at 34 yds, shots are lower .

Does that make sense or perhaps it is just me?

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There were a lot of posts/responses to Dan's original question, and I would like to summarize at least my understanding...

1. From what I understand, if you have "either" an SFP or FFP scope (not inexpensive); and if you zero at 25 yards @ 6 power, your POI will NOT shift even if you change to maximum magnification and still shoot at 25 yard zero? Please answer Yes/no and if "no" why not?

2. Same as above but if you zero @ 25 yards and change magnification from 6X to 13X and also "change" shooting distance to 34 yards, you WILL have POI shift, as Dan did in his experience? Please answer yes/no and if "no" why not

I believe the correct answers to both #1 and #2 are YES, but want to be sure.

Thanks

 

[Scotchmo]

OP's original question below:

"I zeroed my scope at 25 yds at 6 power, if I change to 13 power (the max) out at 34 yds, shots are lower .

Does that make sense or perhaps it is just me?

===========================================================================================================

There were a lot of posts/responses to Dan's original question, and I would like to summarize at least my understanding...

1. From what I understand, if you have "either" an SFP or FFP scope (not inexpensive); and if you zero at 25 yards @ 6 power, your POI will NOT shift even if you change to maximum magnification and still shoot at 25 yard zero? Please answer Yes/no and if "no" why not?

2. Same as above but if you zero @ 25 yards and change magnification from 6X to 13X and also "change" shooting distance to 34 yards, you WILL have POI shift, as Dan did in his experience? Please answer yes/no and if "no" why not

I believe the correct answers to both #1 and #2 are YES, but want to be sure.

Thanks

1. If you do everything correct, then YES. If not, then NO. You must also correct for parallax whenever you shoot at a different magnification. And the numbers on the parallax dial are rarely exact. Unless your eye position is perfectly on center, the amount of parallax error at one magnification can be different than at another magnification, resulting in a different POI.

2. YES or NO. Definitely YES if the apex of the trajectory is at 25 yards, then it will hit low at 34 yards when using a 25 yard zero. Though that is a result of normal drop and not really a "POI shift". But if the apex of the trajectory is at 30 yards, then the 25 yard and 34 yard zeros will be about the same, so the POI should be good at both distances.

It's possible that the OP's scope is fine and that he is simply not accounting for the change in parallax at the different magnifications.

 

[Dan_Br]

I think it was more "me" than anything else. I firmed up the shooting table and am getting better hits at different magnifications. I still think the variable is my ability to hold steady.

thanks to all who responded, and once I learned that it should not be the scope, I could concentrate on the weakest link....me

dan

 

[bubblerboy64]

Ok for my two cents. The point of impact should not change when you changing powers AS LONG AS you are speaking of the center aiming point of the reticle regardless of whether you are talking first focal plane or not. BUT there is a thing called parallax which could come into play. I'll not get to deeply into explaining parallax but essentially it relates to position of your eye behind the scope. If you change power you very well could be changing your eye position just enough to bring parallax into play. From what's being described it's more likely something wrong with the scope but I'd consider the parallax deal and be as certain as you can be that your eye position doesn't change from directly centered behind the scope. Hope this is of some help.

What I would do is to very solidly fix your gun on a good rest and get a good target image in the scope and then have a second person turn the power up and down. You have to absolutely have the gun nailed down so that it can't move. Under this situation if the cross hair or what ever is in the center of the reticle moves on the target you've got a scope problem.

Now once you move off the VERY CENTER of the reticle( unless it's FFP) then totally different situation. Again hope this helps.