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Tuning Fliers-at then end of my wits

I have, over the last 4 months, shot more than 4000 H&N slugs (25, 27 and some 30 grainers) through a number of different liners in my two Impacts. I have never seen a projectile this consistent in all my years of shooting air rifles. Fliers are extremely rare and even then, maybe my concentration had lapsed or a gust of wind had suddenly come up. 

In my blue-printed Impact, I have not had a group open up at 100m over the last 500 shots, all with H&N 27grain slugs. 

I do wash them and spray them with silicone. A few friends don’t, and they do not seem worse off.



 
Sounds like harmonic problems, could be the barrel liner lock nut tension. I would readjust it, then test the rifle shooting with reg and hammer set real low (~750fps). If it's still flinging random flyers, try readjusting thr long nut again.

I take care of my barrels, but I had a couple of FX liners that went from hero to zero. It wasn't until I got a new Hawkeye borescope with the 90 degree mirror attachment that I found some crazy damage that I was luckily able to fix. Goes to shoe that you you don't really know what's going on inside the bore until you actually get eyeballs in there. Fortunately, liners are relatively cheap to replace.
 
Mike, I can't know specifically what your problem may be, but, it sounds like you have addressed the variables, and the same rifle/pellet combo that was shooting well, is now not shooting well. Since the chrono indicates nothing obviously wrong inside that would lead to inconsistent velocity, I believe the issue is in the barrel system somewhere. It could be either stubborn leading, cleaning damage, or the assembly itself with its various components. It would be interesting to see if a different liner showed similar results. My only similar experience was with an FX Crown, but a different problem. The groups were usually good, but the POI would change frequently, and for no diagnosed reason. 
 
One of many things I don’t understand is how barrel leading , damage or any other mechanical issues would produce fliers. Since these issues are always there it would seem to be all of those issues would result in larger groups not fliers. Fliers would have to be caused by some issue that is NOT always there. Something like a slight wind change, shooter error or pellet defect. It essentially how you define flier but it’s an important consideration. My guess is for most of us fliers are shooter error and you won’t solve that tweaking on the gun. RIGHT? 
 
Of course shooter error is a factor, and I don't claim to be a master bench shooter by any means, but in my experience that's a matter of a shot spoiling a good group, say opening a half-inch group to an inch at 70 yds. I'm talking about half-inch groups opening to 1.5 inches or worse, often with three touching and one in a different zip code.

Washing and lubing the H&N slugs didn't help. NSA 23 gr .217 slugs did better but nothing like I had before with the H&N. Put in my old Slug A liner. We'll see.
 
It took 25 years for me to finally set my ego aside when issues popped up with my long range shooting and finally look at myself first. The last 15 years have been way better. It’s way cheaper and less time consuming than constantly blaming the gun, load or ammo. Sometimes it is the gun but I’ve developed ways to test me just like we test equipment. Sometimes when we get frustrated, we only get worse because we lost our confidence in the gun. The fact that you still have a flier problem with pellets raises an eyebrow.

I'm serious about this. Weaponology showed with a neural scan a pro shooters groups shrunk in half when he was in the relaxed zone. I don't remember if it was Alpha or Beta brain waves but basically when you clear your mind, your dead on. It's not just breathing and form. You have to truly learn to relax. Probably really hard in a competition but just something to think about. I personally only want to shoot when I'm able to relax and it helps me do it further.


Years ago I was on a prescription pill for high blood pressure (propranolol) which is also a beta blocker (banned in the Olympics). I shot ridiculously small groups when I was out load testing with my centerfire rifles.
 
A gust of wind can easily do that. Even one you might entirely fail to notice. Are you using fine wind flags-yarn or old video tape or something similar? But it certainly could be other things as many have mentioned. As to barrel leading, it seems that an excessive buildup of lead in the barrel could be intermittently "sluffing off" small bits and possibly changing POI through disruption of stability upon exiting muzzle or possibly even fragments being picked up by a pellet with flight disruption. Certainly not something I've seen verified but it seems like a possiblity.
 
I have three wind flags at 20, 40, and 60 yards, all light surveyor's tape, all long so they are sensitive. Around here it's not unusual for each to point in a different direction. I test accuracy early in the morning when it's calm. I've been able to look at my flags and estimate my hold-off with pretty good success when there's a breeze, if it's constant. Too windy and shifty today to judge accuracy. I don't have any health problems, no real stress these days- retired 5 months ago. Been an airgunner since the early 80s, shot NRA bullseye twice a week in the mid-90s, weekly 10-meter air pistol 1996-2014, got my first PCP rifle 2015. I have a bubble level mounted to the scope. I shoot at 30 yds and if group is one-hole tight, go to 70. I learned in the 80s how much more important follow-through is when barrel time is long. My liner and barrel sleeve seem pretty straight when rolled on a glass plate. Did the JB thing on my Superior liner without improvement. Tomorrow may try without bipod. Have a good bag setup.
 
Fully agree on the dwell time in barrel for airguns. That makes consistency even more important than with centerfires or even rimfires. I would be highly surprised if you don't see improvement by shooting off a bag vs. the bipod but could be dead wrong. With my springers shot off a bag, I've noticed that those with a relatively flat bottom show less "finicky" behavior in regard to rest position than do those with less flat bottoms, and my personal belief is that a lot of the changes seen can be attributed to different movement across such a curved (or severely slanted) lower surface on a rest. Combine such a possibility with the susceptibility of pellets to wind displacement (especially with any noticeable variation in wind strength/direction) and it's amazing that air guns can shoot as well as they often do.
 
Of course shooter error is a factor, and I don't claim to be a master bench shooter by any means, but in my experience that's a matter of a shot spoiling a good group, say opening a half-inch group to an inch at 70 yds. I'm talking about half-inch groups opening to 1.5 inches or worse, often with three touching and one in a different zip code.

Washing and lubing the H&N slugs didn't help. NSA 23 gr .217 slugs did better but nothing like I had before with the H&N. Put in my old Slug A liner. We'll see.

The big flier that you’re dealing with is very disturbing. I can see why you would question shooter error. Usually when we fling one, you can call it because of what you saw your crosshairs do in that final millisecond. Here is my take on blaming it on a bad batch of slugs. If you do indeed have a bad batch, why is it only one out of 4 or 5. What are the odds that you couldn’t at least shoot 4 bad ones and only 1 good one and just have a giant group of fliers. Very frustrating but airguns can be fickle. When my Impact starts flinging a couple, I put it away until the next day and it’s always fine. I have learned to not start twisting knobs and buying things the second the gun, or me possibly, starts acting weird. Good luck.
 
Definitely agree with the magazine as a possibility. It seems that plastic air gun mags could have defects in several areas. I have a Taurus 17HMR revolver that is extremely accurate if I avoid one chamber. The indexing slot on the cylinder for that particular chamber is a few thousandths wider than all the others and that chamber always shoots a bit off. If such is possible with a metal mechanism then it surely seems possible with a plastic mechanism.
 
I have been single-loading using a CARM loader for six months, only using mags in the field. This morning with no wind I still get wild fliers. They happen with my previously reliable 23 gr H&N slugs, but also with 23 gr NSAs, which have never worked well in this gun. Hybrids, Knock Outs in various sizes have all been poor in the past. Have to ask myself how much more time and $$ I want to invest.

It's possible I have two bad scopes. Took off my 'good' scope and shipped back to maker, who immediately offered a replacement. Great service. Meanwhile put on my old Optisan EVX, but no improvement. So I'll wait for the replacement scope. If that doesn't fix things, I think I'm done.