I FEEL LIKE IM TAKING CRAZY PILLS! 0.8 Mil Vertical Zero Shift Session To Session

[HandgunHTR]

First off, how big are your 5-round groups?

Second, when you are shooting for zero, how many shots are you shooting?

If all you are shooting is 5-round groups, then there is a very good possibility that your zero check groups are actually falling within your cone of impact.

Before you start taking stuff apart, shoot a 20, or better yet a 30-round group to get your true cone of impact and your true zero.

If you did do a 20 or 30 round test to determine your system capability and true zero, and are using that to confirm that you are indeed getting a zero shift, don’t rule out focus and parallax as a potential cause. Most people I know have never taken the time to accurately set up their focus so that the parallax settings are true.

 

[Macintosh]

It’s strange that every time you adjust, when you go back to your other location you are off exactly the amount that you adjusted. If I understand correctly that was consistent multiple times. Makes me think it’s something about the location, not the setup…shot angle not accounted for + Ranges not exactly 100 yards?
0.8mil is a lot though. Hard to think of non-obvious changes that would account for a consistent shift that large.

Can you confirm 0.8mil= center of your 100 yard groups are off from previous zero by roughly 2.75”? How big are your group extreme spreads/how many shots are your zero groups? (I see now you said 5-round groups. 10-round zero groups would allow you to be much more definitive in identifying the true zero. Probably not the entire issue, but quite possibly part of the issue)

To test if some “thing” is the culprit, you change only that thing and check function. So, to test it, you could zero at home, go to the other range and see if its .8 off again—but DONT adjust. Shoot and see if it is consistent though. Then go back home. If its still zeroed at home, Im betting it has to be something different between the ranges. .8mil is a ton for any one factor to cause, but with such a consistent error exactly matching your adjustments, I cant think what else it could be.

 

[TaperPin]

How much wind would you expect to cause a 0.8MRAD vertical shift at 100m with a .308?

You believe what you want to believe.

 

[Bluumoon]

Put it back together and do a drop test (on correct surface). I’m sick of seeing shifts even following the mounting/torque guides, each rifle is getting dropped after assembly now to make sure I got it right.

 

[Sadie]

Mirage could be part of it.

 

[WCB]

quickest most simple thing is just throw your old scope on it and shoot it. Not sure why you would take everything completely apart when the only change was rings and optic. Just reverse change and test.

 

[Marbles]

quickest most simple thing is just throw your old scope on it and shoot it. Not sure why you would take everything completely apart when the only change was rings and optic. Just reverse change and test.

Very easy if using a pic rail and having rings for each scope. Easy enough if 2 scopes with UM rings.

Unless I'm mistaken, he has to pull his scope from the rings as the rings screw directly to the action.

Personally, while not hard, I hate putting the scope from rings.

 

[SloppyJ]

Rings? Surprised no one has mentioned it.

 

[SkeeterMcgiblet]

I'm probably going to disappoint a lot of people but I never ended up methodically chasing down the zero shift error. I had my first NRL hunter shoot over the weekend so I spazzed out, tore the rifle down and reassembled with the UM rings that came in just in just in time.

One major takeaway from removing the original "possible problem" rings: the blue loctite I used was still liquid in many areas where it didn't anaerobically set up, most notably some must have spilled out from the ring cap holes and got on the scope tube, and a few of the screws themselves. The scope was mounted all the way forward so the "occular assembly" was tight to the rear ring. I almost wonder if the liquid loctite could have cause a very very slight straight forward shift at some point resulting in the vertical only error and slid back to being tight after a bump or during travel. This seems crazy to me considering the locitite was still wet a few weeks after install in dry Colorado.

 

[Formidilosus]

I'm probably going to disappoint a lot of people but I never ended up methodically chasing down the zero shift error. I had my first NRL hunter shoot over the weekend so I spazzed out, tore the rifle down and reassembled with the UM rings that came in just in just in time.

One major takeaway from removing the original "possible problem" rings: the blue loctite I used was still liquid in many areas where it didn't anaerobically set up, most notably some must have spilled out from the ring cap holes and got on the scope tube, and a few of the screws themselves. The scope was mounted all the way forward so the "occular assembly" was tight to the rear ring. I almost wonder if the liquid loctite could have cause a very very slight straight forward shift at some point resulting in the vertical only error and slid back to being tight after a bump or during travel. This seems crazy to me considering the locitite was still wet a few weeks after install in dry Colorado.

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Not crazy at all. Loctite not setting has been discussed- with those having problems with it being told they are wrong and ignorant of how to mount scopes. Fingernail polish is your friend.


And, the rings must be only on the tube, not remotely touching the objective or ocular.

 

[WCB]

Very easy if using a pic rail and having rings for each scope. Easy enough if 2 scopes with UM rings.

Unless I'm mistaken, he has to pull his scope from the rings as the rings screw directly to the action.

Personally, while not hard, I hate putting the scope from rings.

Weather the rings mount directly to the firearm or not it would take the same amount of time and effort. Two mount screws into the top of the action or a cross bolt from ring to base. replacing rings and scope is like a 10minute process even if he took direct mount rings off and added a pic rail.

A lot faster than breaking the entire gun down including rings and bases and reassembling when the only change he made was mounts and optic.

 

[SkeeterMcgiblet]

I'm probably going to disappoint a lot of people but I never ended up methodically chasing down the zero shift error. I had my first NRL hunter shoot over the weekend so I spazzed out, tore the rifle down and reassembled with the UM rings that came in just in just in time.

One major takeaway from removing the original "possible problem" rings: the blue loctite I used was still liquid in many areas where it didn't anaerobically set up, most notably some must have spilled out from the ring cap holes and got on the scope tube, and a few of the screws themselves. The scope was mounted all the way forward so the "occular assembly" was tight to the rear ring. I almost wonder if the liquid loctite could have cause a very very slight straight forward shift at some point resulting in the vertical only error and slid back to being tight after a bump or during travel. This seems crazy to me considering the locitite was still wet a few weeks after install in dry Colorado.

Also for reference this was the zero and groups I got on the first day of the scope with the original rings. To go from this to .8 mil (~2.9") high them low seemed like a true mechanical failure, not just me sucking.

Federal Gold Medal Match 175s (Prone, Bipod & Rear Bag in the dirt):
Middle 3 rd (zero check after 50 yard bore sight and rough zero, got lucky and pretty much perfect)
Middle Top 5 rd
Top Right 8 rd (all I had left in box, sorry no 10 rd)

Misc "Hunting Loads" and bulk ammo at Top Left, Bottom Left, Bottom Right. I know they are sinful 3 rd groups but I just to see if rifle liked them.


I'd also really like to thank everyone who's weighed in, although I didn't follow this through to the end since I was already planning scope mount changes I really appreciate and will remember everyone's advice for future troubleshooting.

 

[SkeeterMcgiblet]

Not crazy at all. Loctite not setting has been discussed- with those having problems with it being told they are wrong and ignorant of how to mount scopes. Fingernail polish is your friend.


And, the rings must be only on the tube, not remotely touching the objective or ocular.

Very good to know, I guess I never came across a case where it stayed liquid and was this sloppy before, I assumed it would eventually dry out. This time around with the UM rings I paint penned everything and put witness marks.

For future reference why is it bad practice to have scope mount touching the ocular assembly? Luckily I didn't do this on the the new UM rings due to pin locations but I was pretty close for best eye relief.

 

[Marbles]

Weather the rings mount directly to the firearm or not it would take the same amount of time and effort. Two mount screws into the top of the action or a cross bolt from ring to base. replacing rings and scope is like a 10minute process even if he took direct mount rings off and added a pic rail.

A lot faster than breaking the entire gun down including rings and bases and reassembling when the only change he made was mounts and optic.

I don't think you comprehend what I wrote or the point of it.

 

[Marbles]

Not crazy at all. Loctite not setting has been discussed- with those having problems with it being told they are wrong and ignorant of how to mount scopes. Fingernail polish is your friend.


And, the rings must be only on the tube, not remotely touching the objective or ocular.

The last thing I put together with nail polish was action screws several months back, when I pulled them the other day the nail polish was still wet.

I have had loctite still be wet as, but not since I started shaking the tub before application and cleaning with acetone.

From my personal experience, both can fail to set.

 

[WoolyBugger]

I wonder if the ring riding against the ocular was causing this. if the very rear of the ring was ever so slightly onto the angle of the assembly and not getting a solid enough grip. Should be clamping straight down with no obstruction, I think up against that angled piece might be affecting that at the least. Edit: hard to tell on your pic how close it is so could be wrong

 

[SkeeterMcgiblet]

I wonder if the ring riding against the ocular was causing this. if the very rear of the ring was ever so slightly onto the angle of the assembly and not getting a solid enough grip. Should be clamping straight down with no obstruction, I think up against that angled piece might be affecting that at the least. Edit: hard to tell on your pic how close it is so could be wrong

I'm suspecting this as well too, I didn't push the ring up against the ocular but it was riding tight. The Maven seems to have a generous eye box and I had to push it as far forward as possible get optimal eye relief. I did address this with my new UM ring set up so all should be good.

 

[Wrench]

You'll know if you pop the cap off. If it marred the scope....it's possible.

 

[blkqi]

For future reference why is it bad practice to have scope mount touching the ocular assembly? Luckily I didn't do this on the the new UM rings due to pin locations but I was pretty close for best eye relief.

so that the rings do not impinge on the riflescope internals (erector and parallax assemblies).

 

[Formidilosus]

The last thing I put together with nail polish was action screws several months back, when I pulled them the other day the nail polish was still wet.

I have had loctite still be wet as, but not since I started shaking the tub before application and cleaning with acetone.

From my personal experience, both can fail to set.

What type was it? Nail polish, nor paint will dry in a totally airtight situation.