Please help me understand this...

[Mossonarock]

I have two underlever rifles from the same manufacturer, same caliber. The cocking lever on both of them came loose. There's a way to tighten them up that was engineered on the cocking lever. Tightening them up doesn't necessarily lengthen or shorten the cocking levers but could be used to do so. So, I tightened them up without changing their lengths and thought "great I should be getting tighter groups again." Wrong!

One rifle was no longer hitting the pellet catcher at 25 yards. huh?! Without making any adjustments to this rifle, I went to the other to see how it was doing. The other rifle hit the pellet catcher and made a neat 3 shot group with two of the pellet holes touching each other at 25 yards but the group was about 2 mildots high. Again, huh?! So I adjusted the vertical elevation on the scope by that amount to lower the poi. Then, the shots were about 2 mildots too low. So, how does a two mildot adjustment become 4? Ok, now I think the expletives I was hurling were more on target than any of these pellets were going. The sun was going down so I put the rifles down.

Why would tightening up the screws on a loose cocking lever cause such wild loss of accuracy? And why would that accuracy not be resolved with adjustments to the scope on the one rifle? I still haven't tried making any adjustments to the scope on the first rifle. I'll be taking these rifles down to 10 yards this evening (if I don't have to work late clinic) since shooting at 25 yards isn't even safe. I'm so dumbfounded by this. They should be more accurate and more consistent now that the cocking levers are secured again. Story of my life. Do the right thing and the wrong thing ends up happening anyway and gets even worse... I think the common phrase is "can't win for losing."

[Lefusil]

That is weird.  Stuff like this happens to me all the time (at work and shooting).  You may want to try and isolate the cause, is it the lever , or the scope.
Have you tried loosening the cocking lever bolt(s) again, to see if POI moves again?
Likewise with the scope setting, verify if the change you made is reversible.
Do the two guns respond differently or the same to a given change?
Its just a puzzle to be solved.

[Muddydogz]

Vibration, tension? Don't know but I do know it doesn't take much to throw a springer off it's mojo. I would tighten everything down good, locktite what you can and resight. Good luck

[Roadworthy]

You are seeking suggestions without really identifying the problem.  We have no way of knowing what model airguns you are adjusting nor what adjustments you are making.  With so little data shared and suspecting these are both new airguns I'll take a stab in the dark and suggesting cleaning both barrels well.  Follow up by checking stock and scope screws for proper tightness.  Now shoot the guns again to see what changes you've made.

[DanD]

Regarding the poi change, here's my guess-  If you changed the the cam-over pressure pushing against the action when the lever is closed, the action is slightly warped in relation to its previous adjustment, changing the poi.

[Mossonarock]

Y'all, Thanks for responding.

Dan- That's what I would have thought. However, the cam-over pressure you are referring to shouldn't have changed- maybe it has some how idk. The tightening mechanism on the lever can only be done in increments. I set it at the same increment that it was at. I just tightened the screws that holds it there. A slight change in poi wouldn't have surprised me but pellets entirely missing the pellet catcher??

Roadworthy, If I could identify the problem, I wouldn't be here asking. I gave you all the data I have. I tightened the grub screws holding the cocking lever together. Now the shots are going all over the place. These aren't new rifles. I've had them almost a year.  Its not a bad suggestion to try cleaning the barrels; although, its probably unrelated and won't make a difference. Everything else on the rifles are tight. I check those all the time. That's how I found the cocking levers being loose. You'd expect tightening them would not cause worse accuracy. I didn't mention the rifles make/model for a reason. Let's just say that these rifles were about as accurate as my HW97kt in my hands.

Muddydogz and Lefusil. Aint that the truth... I won't be able to get out again for a couple days to try "screwing" with the nuts and bolts some more to see if the problem mysteriously clears up, reveals itself or gets worse. So frustrating. I wouldn't be surprised if I got all three -the problem clears itself up, reveals itself, and gets worse all that the same time!

[Duckfish]

Very secretive!     

Let's see...Diana?     Gamo?      Browning?    Air arms?     You already have a Weihrauch so that can't be it. 

I give up.      Wait, grub screws hold the lever together, that's right you didn't say it was a spring gun it could be a Benjamin pneumatic pump, those are under lever's aren't they?   Is it a Chinese clone?   A Hatsan, I don't know if they make an under lever.    Let's see..... I guess I'm done guessing!  Thanks for the exercise it was fun.

Oh, oh, wait I've got it!   .      When you changed how the arm closed you unseated the breach seal, totally the cause of your loss of poi.  Problem solved!   

Oh wait Dan already said that, sorry.

[avator]

With the lack of specifics my first thought was broken main springs.

[K.O.]

without knowing which rifles it becomes this it a test...

[fwbsport]

I've had underlevers before and now.

The "now" underlevers are HW57, 97 and I had an Eclipse .25 with low velocity but high power when it hit.

Anyway, the 57 is very "loose jointed" and this appears to be a design defect of using the lightest parts to make it.  The looseness doesn't affect performance.
The 97 is a workhorse heavy underlever that I hate firing because of its size and weight and Thumbhole stock. I hate it.

The lever system on the 97 is supremely solid but the gun always loosens up and needs re-tightening. Furthermore, the 97 is supposed to be more accurate than an R1 or HW80 and to me it is not.  I think the underlever system in general is subject to more moving parts that just loosen in time.

[lefteyeshot]

On the first gun, if the cocking lever touching the barrel now or tightened it might have changed the harmonics of the vibration.

When I haven't shot a gun in awhile or I haven't shot in a while the first shots are usually off until I warm up some, get in the zone, then POI usually gets back to POA. If not I re-zero. Might be hotter or cooler that day. I usually shoot 10-20 pellets before I worry if the gun is still zeroed or off. Too much coffee or nicotine causes a flyer now and then

I was shooting .22 RWS super domes from my Mendoza made Hammerli badged X2 dual cal and noticed some pellets fit snug and some loose. The snug one shot good, the loose ones were off a little.

[fwbsport]

Tim,

your message

"I was shooting .22 RWS super domes from my Mendoza made Hammerli badged X2 dual cal and noticed some pellets fit snug and some loose."

Yes! I was shooting domes from Crossman (10.5gr) and noticed loose and tight fitting pellets in my HW 50 .177.  Then when I put them in my FWB Sport they were all tight but some were "not as tight."

I decided not to use Crossman Premiers in my FWB anymore!

Now I am shooting Barracudas from HN Sport.  They are actually heavier than the CPs but they are more uniform.  They hit to the same point of impact.

[lefteyeshot]

Maybe seating the loose one would help. I don't know.  If I shoot good that's good, if not so good that's good also, I'm shooting.

[Roadworthy]

All under lever spring piston airguns do not operate in exactly the same manner.  The better ones (at least more expensive) tend to have a moving compression tube which cocks the piston.  The cocking lever then moves the compression tube to battery for firing.  Other under levers simply cock the piston with a lever instead of the barrel.  In the first type the cocking lever has two functions.  In the second type it has only one function.  More information might help identify the problem.

[Mark 611]

Thomas is right without knowing what u have its hard for us to help u!!!!!

[Mossonarock]

Well, the main reason I didn't want to mention the make/model is because I wanted people to think more in terms of theory and offer insight rather than model specific mechanics. I hope that makes sense. And I think y'all have done that. Thank you. Its really amazing how sensitive springers can be. Turn a screw a wee bit and its mojo gets all thrown off. Its like they are 2 year old humans.

The rifles in question are Hatsan Dominator .25 cal in spring and vortex. Yesterday, I took the spring Dominator in to the basement for some 10yd target shooting. I think I might have gotten it back to shooting pellet on pellet at ten yards. I still can't understand why the poi got so far off from poa just from tightening some grub screws on the cocking lever. Hopefully, this weekend I'll be able to take it back out for some 25 and 35 yd target shooting and see what it does. The scope on both rifles are utg/leapers. They usually hold their zero very well. So, I don't get it.

My vortex dominator has always been difficult to shoot tight groups. However, I don't have a pump. So, I haven't been able to modify the pressure in the piston. I think the pressure really needs to be bled off a bit and that might reduce the recoil. But that doesn't explain why the accuracy was so bad. Its the vortex rifle that wouldn't even hit the back stop, group or nothing just from tightening up the grub screws on the cocking lever.

As I stated above, I didn't adjust the length of the cocking lever when I tightened the grub screws. I never even knew the length of the cocking lever could be adjusted till all this came loose this week on both rifles. Its not in the owner's manual and I've never heard it mentioned by anyone either- another reason why I didn't bother mentioning make/model. I plan to post about it in the Turkish rifles gate. It really is an intriguing design feature. I think the Dominators had a lot more going for them than even Hatsan had realized. However, it sure would have been nice if they paid a bit more attention to QA during production.

[fwbsport]

Tim,

I have the HW underlevers and neither of them are consistent shooters--they hit a spot for awhile and eventually it is as if my scope shifted.  I have found the problem to be the way the underlever is compared to just a simple break barrel.

[avator]

Well, the main reason I didn't want to mention the make/model is because I wanted people to think more in terms of theory and offer insight rather than model specific mechanics. I hope that makes sense. And I think y'all have done that. Thank you. Its really amazing how sensitive springers can be. Turn a screw a wee bit and its mojo gets all thrown off. Its like they are 2 year old humans.

The rifles in question are Hatsan Dominator .25 cal in spring and vortex. Yesterday, I took the spring Dominator in to the basement for some 10yd target shooting. I think I might have gotten it back to shooting pellet on pellet at ten yards. I still can't understand why the poi got so far off from poa just from tightening some grub screws on the cocking lever. Hopefully, this weekend I'll be able to take it back out for some 25 and 35 yd target shooting and see what it does. The scope on both rifles are utg/leapers. They usually hold their zero very well. So, I don't get it.

My vortex dominator has always been difficult to shoot tight groups. However, I don't have a pump. So, I haven't been able to modify the pressure in the piston. I think the pressure really needs to be bled off a bit and that might reduce the recoil. But that doesn't explain why the accuracy was so bad. Its the vortex rifle that wouldn't even hit the back stop, group or nothing just from tightening up the grub screws on the cocking lever.

As I stated above, I didn't adjust the length of the cocking lever when I tightened the grub screws. I never even knew the length of the cocking lever could be adjusted till all this came loose this week on both rifles. Its not in the owner's manual and I've never heard it mentioned by anyone either- another reason why I didn't bother mentioning make/model. I plan to post about it in the Turkish rifles gate. It really is an intriguing design feature. I think the Dominators had a lot more going for them than even Hatsan had realized. However, it sure would have been nice if they paid a bit more attention to QA during production.

Now I see how silly my first comment must have sounded.

[fwbsport]

Today I am eating my words about my 97K. 
I am blaming this site (or attributing to this site!) for this sudden attention to my 97K. 
It's shooting fine mostly because I have screw torque lowered on the stock screws.  Before I tightened them pretty snug but now without being such a gorilla on the screws for the wood I've found a more peaceful nation of underlever shooting!
 

[nced]

Today I am eating my words about my 97K. 
I am blaming this site (or attributing to this site!) for this sudden attention to my 97K. 
It's shooting fine mostly because I have screw torque lowered on the stock screws.  Before I tightened them pretty snug but now without being such a gorilla on the screws for the wood I've found a more peaceful nation of underlever shooting!
 

Here are the stock tightening specs for HW springers per HW in Germany……….
Front stock screws = 2.5 Nm is equal approximately to 22.1 in-lb, and Large trigger guard screw = 5 Nm is equal to 44.3 in-lb, and rear trigger guard screw = 2.5 Nm is equal approximately to 22.1 in-lb.

Convert newton meters to inch pounds:
http://www.convertunits.com/from/newton+meters/to/inch+pounds

I've personally "steel posted my large trigger guard screw and added piloted steel screw cups to my R9 and HW95 stock screws. This allows me to torque the screws tight without concern for crushing the wood under the screw heads...............