Tuning Needing to re-zero

[MrP]

Where should I be looking if, every time i shoot, i have to make small adjustments to my scope at the start? 


I have one gun where I can always shoot decent groups eventually but I find myself having to rezero a little after every fill. 

I can tell there aren't any screws loose anywhere other than in my head, so I don't think anything is working it's way loose but maybe I'm missing a screw somewhere. 

Since it's unregulated the shot string changes over time and I'm guessing that (due to some barrel harmonics thing or another), where I have the zero point when I'm shooting at the end of the string is different than the start so I have to do this every time. 

 

[Gerry52]

After filling, don'tr re-zero till after you've taken 5 or so shots. SOME guns need a few shots to "settle" after filling. Works for me, hope it works for you. 

 

[JW652]

If neither the stock nor scope screws are loose, I can think of two potential issues. First it the scope itself. For me, it has proven best to use a known scope that has never presented any past problems. A new scope and rifle introduces a lot of variables. The other factor may be hold. I put a level on the rifle first thing so that if there is cant, it is always in the same direction. Initial testing with a scope of that has shown consistant reliability and nestled in the hands or on bags in the exact same way for each shot will show you what pellets it prefers and and if any issues exist with the rifle or shooter.

Once the soundness of the platform is assured, I level the scope and rifle to each other and the bore, degrease and purple Loctite (222) all screws and make final adjustments This isolation of potential issues is the only way that I can get my head around everything.

Enjoy!

 

[Odoyle]

What gun and scope exactly?

 

[MrP]

It's a custom airforce, shooting at higher power, with a cheap $70 Feyachi scope with the scope rings that came with my gamo swarm magnum. If the solution is a multi hundred dollar scope and $100+ scope rings then I guess it's back to iron sights for me. I can't indulge myself quite that much... mouths to feed and all that.

I have paid a lot of attention to the angle of my eye relative to the scope and I found some ways to ensure that it is consistent. So I THINK I can tell the difference between an issue with alignment of the hardware on the one hand, and my own personal alignment and hold issues on the other. I feel like I've eliminated my own sources of variation (or at least identified what they are).

Maybe I am seeing changing barrel behavior as fpe climbs. All of this could just be reflecting the fact that I start shooting at lower energy in a shot string and generally increase throughout the shot string. If it was just vertical differences I would attribute it only to that but there is some shift from left to right as well. It kind of feels like focus gradually shifts as power increases through the shot cycle and I'm not 100% sure if that's repeatable or if it was just a coincidence the last couple of times.

So for example my first 10 shots will be a little bit to the right and then I zero, and by the end maybe it's shooting a little bit to the left. 



Thank you jw652 for that procedure. Loctite - hadn't crossed my mind.

 

[Odoyle]

It's good to have a Leupold EFR (at least a 3-9x) as a spare for a trusted second opinion. A lot of aggravation and grief had been spared by a trusty old Leupold EFR (and Japan made Weaver V16 as well as Japanese Bushnell Elites) vs ANY scope (AT ANY PRICE) made in China. 

 

[MrP]

I've learned the hard way that when people with experience like yourself (odoyle) come down firmly on something like this that i usually find myself wishing I'd listened! 

I can't bring myself drop $400-$900 on a scope... is it not going to happen? 2x-7x is fine or even fixed zoom 

 

[dannya1a]

I think the biggest POI/POA issue is down to this being an unregulated gun. It has a known shot cure and likes to be within a certain pressure ranges to limit the POI/POA wandering. I have a .25 cal condor. I have half a mind to sell it on. I don't like how particular it is in this area. And the accuracy isn't what my gauntlet or Impact is. But then again it isn't know to be able to stack tight groups either. its is mainly just a 1" group type of gun. Good for body kill zone shots on medium game, not pinpoint head shot capable.

 

[MrP]

That's an interesting thought. So lateral drift in zero point could be a sign of changes in power in an unregulated gun and not necessarily loose parts?


Do all of you are reading this generally concur the Air Force airguns are not really capable of high levels of accuracy? Surprised me but it kind of makes sense when I think about it.

 

[c_m_shooter]

If it is an Air Force gun, it could be you are not holding it consitant enough. My Air Force Condor is as hold sensitive as a springer.

 

[c_m_shooter]

It also seems like false economy insisting on using a $100 scope on a $1000 dollar rifle.

 

[MrP]

Good point! sometimes when you're on a budget you just have to choose where to invest at any given point in time. Time is a factor. As I said iron sights work for me I've always enjoyed open sights shooting red dots no big deal.

 

[MrP]

I was thinking there's kind of different levels of luxury and economy here. $100, $400, $900, $1500 What is the magic number just to hold zero?

For example what would I need to spend just to get a basic scope that held zero. I don't care about huge zoom range super bright illuminated reticle high-quality Japanese optics any of that.

just hold zero, limited zoom. You would think that would be the starting point for just a minimally acceptable scope. What would you get me that? I actually think I might have it with that $70fWhat would you get me that? I actually think I might have it with that $70 feyachi 2-7x I am thinking point of impact shifts are probably due to the fact that the gun isn't regulated and it does something different at different pressures.

 

[c_m_shooter]

You still haven't told us what rifle you are shooting specifically. Air Force rifles can be all over the place as far as tuning and pressure preferences. What kind of shot strings are getting over the chronograph?

 

[KatoKevin454]

I have guns that change POI due to temp changes, and cheap scopes, to be expected with cheap Chinese scopes, my Athlon scopes seem to do fine, my Discovery scopes have POI issues when temp changes, we get about 40 degree temp changes at our range, 30 to 70 degrees, the metal seems to expand and contract enough to change POI by 1/2" at 25 yards, summer time not so much.

 

[MrP]

cm shooter thanks for your help. I mentioned some but not enough of the details of the gun a few messages back if you are curious, but no shot strings. It is 18" barrel, and a bunch of other parts I changed and added - custom valve, heavy hammer and spring. Not an airforce off the shelf but the frame and trigger are TalonP.

What would you look for in a shot string? It is unregulated and can shoot from 49-130 fpe. Airforce Airgun, indeed they are hold sensitive but that is not a factor in the issue I am seeing. 


Katokevin - i hadn't though of temperature change.... that may well be it! I am shooting in a cold garage at the moment. So the gun is cooling off as i shoot quite a bit. I will try leaving it out for an hour before shooting and see if that has an effect on POI shift.

 

[elh0102]

When you consider the many variables involved, both environmental and mechanical, I believe slight changes in POI are unavoidable. The rifles I always depend on for a hasty squirrel shot are extremely reliable regarding holding zero. But even those rifles, when shot from a steady rest at a small target, will show some small variations. But those variations are much smaller than a squirrel head, so I'm satisfied, and the squirrels are dead. If I were to shoot at a benchrest target for score, I would usually probably need to make a small change. 

 

[MrP]

Helpful, thank you.

 

[Arash]

I found when I tuned reg pressure at high setting I had poi shift. To make a long story short: some times high pressure make some kind of temporary leaking for orings that seals transfer port and barrel. changing this orings regularly is a good idea & never lub them.

Also POI shift at low pressure is usual.

I wont say harmonic is irrelevant here but it hasn't huge impact on result.

 

[Odoyle]

Run it over the chrony and take notes start to end fps and air pressure remaining every shot. Then you know where your optimal start fill pressure should be right before the curve flattens and go from there. Likely less than max pressure unless you are using the tiny TalonP tank.