Zero Shift? Tikka/SWFA/UM Rings

[TX_Diver]

Out of state for a hunt and wanted to shoot the rifle before hand.

I can only post one pic at a time from my phone so there will be a few posts to complete this.

Zero pre trip was based on this 13 rd group and moved up .1 and right .1

 

[TX_Diver]

Pulled over and shot at 620 and noticed I was hitting low so I went to 100 on paper and got this 9 shot group

Prone from pack with binos as rear rest (same as original zero)

Extra target for scale with 1” squares

 

[TX_Diver]

Adjusted up .2 and L .1 and shot this 6 shot group to check zero

This is an old closed road that continues to slope up well beyond what it shows here just in case anyone is concerned from the appearance of the pic.

 

[TX_Diver]

Concerned with why it had moved though I checked all my screws (still tight and the paint marks intact).

Everything was degreased with 99% alcohol and installed with a paint pen and torque driver.


Being a rokslide member I figured I’d do a drop test on my sleeping pad with a case on it. Being low on ammo I just went with 24” as I could measure that with the width of the sleeping pad

 

[TX_Diver]

results of one drop in each side.

1 left side
2 top
3 right/bolt side

 

[TX_Diver]

Concerned a bit but not going to adjust based on that.

So I shot 6 to check again

Noticing that the first mag (top 3) and second mag (bottom 3 that are much tighter) were somewhat different I went to the next step

 

[TX_Diver]

Actually after that I was a bit confused so I dropped it once on each side and shot 1x after each shot

The Kraft diamonds are slightly larger than my previous target which I was out of.

 

[TX_Diver]

Now, referencing back to post 6 where I noticed one group was different than the other I wondered if I was causing issues so i shot 9 building the position each time (starting standing with the rifle strapped to my pack)

9 shots

 

[TX_Diver]

So after all that…



I feel that my original adjustment up and left was valid, but it seems weird that I needed to do that if I can’t really recreate the problem with drops?


I am flying home tomorrow and have another swfa 3-9 that I could bring back but it’s never been used so i have no history with it.

I am very slow to mount and level scopes and really don’t want to do that in a hotel room if I can avoid it…

This combo has never given me issues but I hadn’t shot it much after I last remounted the scope (done the same way I always do, as suggested on here, albeit with alcohol instead of brake clean, and paint instead of loctite this time.

What says rokslide?

System issue?

Poor original zero?

Shooter error (entirely possible)?

Other?

 

[TX_Diver]

Just for reference 18 round group from before remounting scope

 

[huntnful]

Were conditions good when you made that very initial zero? And then similar conditions when you checked zero? Only reason I bring it up is because mirage can really throw a zero off. It looks like you're in the desert in the middle of day, so it could be a reasoning.

 

[TX_Diver]

Were conditions good when you made that very initial zero? And then similar conditions when you checked zero? Only reason I bring it up is because mirage can really throw a zero off. It looks like you're in the desert in the middle of day, so it could be a reasoning.

That’s possible. Today wasn’t too bad but initial zero had some mirage. Not a ton as I shot it fairly slow after mirage being mentioned in another thread. Today there was a little but not bad and I shot my other rifle a bit between groups to keep things cooler.

If that was the case how would someone deal with that?

 

[huntnful]

That’s possible. Today wasn’t too bad but initial zero had some mirage. Not a ton as I shot it fairly slow after mirage being mentioned in another thread. Today there was a little but not bad and I shot my other rifle a bit between groups to keep things cooler.

If that was the case how would someone deal with that?

I personally just shoot zeros first thing in the morning. Like starting before the sun even rises.

THEN, when there is mirage, I know my data can absolutely be skewed. I’ve seen 1 MOA shifts easily when trying to shoot in mirage. I don’t really know how to “deal with it” honestly. I just know to be aware of it, and it’s potential on effecting where the bullet hits.

I never shoot for drop data or zeros in moderate/heavy mirage. Only velocities. But on a hunt, with heavy mirage, I don’t really know how I would approach it. Other than try to get within 400 yards.

 

[BBob]

Today wasn’t too bad but initial zero had some mirage.

Huntful was talking about atmospheric mirage not barrel mirage. If you're seeing it it's most likely atmospheric. The point is If you sight in on a nice early cool morning and head out to shoot in the field on a hot sunny day your zero will be off. Mirage can make the target falsely appear up down left right and in any combination of those at the same time.

 

[BBob]

I don’t really know how I would approach it.

If you have the time you'd try to do just as you would on the range. Observe what it is doing. Is it all vertical? Is it rolling like a river? Is the target bouncing? Is it snapping back to a lower and or sideways and lower position? The quick snap back position gives you a better idea where the real target actually is. You aim and shoot for that spot. If it's steady with no snap back it gets harder. It's more range or field time looking at the mirage, shooting and seeing where it actually goes. That is if you trust your rifle and initial zero and drops.

A trick to watch it better is to back off the focus in your scope or spotter (focus closer than the target). You can see the mirage itself better with the target slightly blurry in the background.

 

[TX_Diver]

Makes sense.

Huntful was talking about atmospheric mirage not barrel mirage. If you're seeing it it's most likely atmospheric. The point is If you sight in on a nice early cool morning and head out to shoot in the field on a hot sunny day your zero will be off. Mirage can make the target falsely appear up down left right and in any combination of those at the same time.

I think atmospheric mirage was worse at original zero. I shot that in TX in the evening but it has been baking all day. Yesterday was hot but it had slowly heated up to that point rather than being 90 since like 9am.

My goal is a sub 400 yard shot anyways but I’m just trying to figure all this out at the same time

 

[BBob]

I think atmospheric mirage was worse at original zero.

Good zeros aren’t always a one and done single range trip thing.

 

[ljalberta]

What were the torque specs used? If everything is mighty tight and seated cleanly, I would begin to suspect the scope.

Although, I would do as Bob suggested and check without mirage first if possible.

 

[TX_Diver]

Good zeros aren’t always a one and done single range trip thing.

Yes. I am learning that!

I liked checking this one by building the position each time too. It gave me a little bigger group but Is probably more realistic than laying down and shooting 10.

 

[BBob]

I liked checking this one by building the position each time too.

That’s great that you are doing that. Shooter inconsistencies are a biggie when it comes to setting up rests and shooting off different types of rests and positions. I know a lot of people that only shoot off the bench with benchrest type rests and bags. When it comes time to shoot in the field things don’t always go so well.