What the heck is going on with my Diana?

[Mr Sasquatch]

I need your help.
 
My D34 (.177) has almost 4,000 pellets through her. After the first 1000 I installed Jim Macarri’s OS kit and did a complete lube job.  Initially I was using Leaper’s 4-12x40 scope with RWS one-piece mount and while the rifle was normally shooting very tight groups, once in while the POI would jump up or down in random intervals. The Leaper’s scope was sent back to the manufacturer for warranty repair at the beginning of this year and in the meantime I installed a brand new CP 4-16x 40 scopes. Soon after that I noticed that the POI is now not jumping but rather” strolling” up and down. 

Here is what I mean. I shot over 23 rows of 5-shot groups, one shot per target . The scope was zeroed prior to this experiment, and the adjustment turrets were never touched after that.   I used the maximum magnification of 16,x and the scope was adjusted for parallax. Shots were fired in my basement with the air temperature around 62 F, from the bench at 10 m distance. The same tin of AA Field 8.4 gr unsorted pellets was used.  All shots were fired with the POA at the center of the black bull’s eye. The tagets are 0.7" in diameter (the size of a dime).

At the beginning (rows #1 and 2), the POI was almost exactly in the center of each target, however starting with row #3 the POI started "walking” upward and stayed off for rows #4,5,6 &7. Actually if rows 4 through 7 were all put on the same target, this would’ve been a very tight group. In row #8 the POI stated drifting down towards the center, overshot a little bit in row #10, but then stayed on the bull’s eye in rows #11, 12 and 13. In row #14 it stated drifting again, this time below the POA. In the middle of row #15 the drift direction reversed itself and in row #16, 17, and 18 the POI was again above the POA, only to start drifting down in row #19. It stayed put for five shots in row #20 and then dropped down in rows #21, 22 and 23. In row #23 the POI started drifting up again.  The up and down drifting continued in this fashion for another 10  5-shot groups ( not shown here) before I had enough of it.

These variations from the POA  are not random like one would expect if they were casued by differences in pellets If I were to plot the distance from POI to POA versus the shot number, the graph would look a sine wave.  So, what the heck is going on with my Diana? Or is this the scope doing it? Any ideas?

[Motorhead]

Scope rings moving on receiver dovetail most likely cause ... or at least worth looking at ?

[Dockey 454]

If the scope isn't moving, then try cleaning your barrel. I have this problem from time to time. Cleaning the barrel usually brings my accuracy back.

[Dockey 454]

One other thing, are you resting the gun directly on the bag, or putting your hand in between the gun and bag.

[thekid]

One other thing, lube the ball and detent, also check your breach seal, see if it needs shimming.
Dental floss works wonders.
Question did you ever change the piston seal, when you installed the kit, if not consider a new one.
The kits do not come with one, this I know.

[RedFeather]

I believe there are two versions of that scope.  One the earlier ones, as someone reported here, the tiny little set screws for the adjustment rings tend to come loose.  Several people have remedied this with locktite and resolved their problem.  This scope got kind of a bad rep for not holding zero the first couple of years.  Wasn't the innards but those screws.  The currently sold models are supposed to correct this.

Re-examining the second target from the bottom, that must be something in the sighting system.  Even with erratic fps (as from a damaged seal) you should not get such a sort of rotating pattern.  I would take off the scope and, if you have irons, shoot another target. 

[Mr Sasquatch]

Thanks for the suggestions so far.

I use Caldwell's Junior front rest and do not touch the forestock with my hands.

I have cleaned the barrel with Goo-gone about 100 shots before the test, and then run dry patches half way through the test.

The ball & detent were lubed well just before I started testing. At the same time I replaced the breach O-ring.

I replaced the original piston seal  with one from JM when installing his kit. Yes, I bought an extra seal.

The stock screws are tighten and set with blue Loctite.

The scope mount screws are all tight, that I'm sure of. But is it possible that the whole dovetail mounting part is not fastened well to the tube? This I'll check tomorrow.

BTW, I tried to use iron sights too, but with my eye sight trying to hit this target at 10 m? A beer can? Yes! A dime? No way.

[BenjiHunter]

On a springer you should always support your gun with your hand, no matter what kind a of rest you use.

[Bullit]

As Redfeather points out.  Check the tiny retainer screws on the windage and elevation turret adjustments for tightness.  Might check the Magnification adjustment ring screw too, while you're at it.  These are tiny screws...like eyeglasses size.

[Mark 611]

if you changed the breech seal they take time to break in! and could take up wards of a few tins of pellets to start sealing right! and another thing I would check is how consistant are the pellets you are using? have you measured them? I'd say IMO that what you are seeing is normal for that type of rifle! it isn't a target rifle! its a break barrel and a entry level gun from Diana not that that's a bad thing but IMO I myself included sometimes expect to much from things and drive myself nut's to make something perfect that just will never be! JMO

[Bullit]

Good point.

[thekid]

This is only at ten yards...

Before this event, were you able to keep all shots in the black, did it always do this.

There is a lot going on when you pull the trigger, your breathing must be the same, hold and head position the same, trigger pull the same, shoulder contact the same.
If shooting in rapid succession, you are going to change the temperature with in the gun, this will affect velocity as well.

I use a standing bench, I shoot at targets that are the size of a pellet hole or at a pellet hole itself.
Seeing I have done my own tuning on this gun and have years of experience with airguns.... it also helps that the man who taught me had extreme sniper skills ( no need to get into details).
If I do my part, at 25 yards I can sink a pellet into a pellet hole ,might not be perfect but it will be in the hole.

So consider, it may not just be the glass or the gun, you may be doing something ever so small to effect the rifle.
Many will say these are not 10 meter match guns, TRUE, but if worked right with the right shooter at the helm, then they become 25 yard guns, from a standing bench.
JMHO

[Mark 611]

Rob I'm thinking the same thing! could be shooter error? not being consistant with the hold? I agree these rifles can be tack drivers if all is working well with the rifle?

[mtsheron70]

Here are some things I have seen posted time to time on shifting POI:

-Check all scope related screws and reset again and loctite them.

-Gun may like a new hold position.

-Never rest a springer direct on a bag.....use your hand to support.

-The gun may like another pellet all of a sudden which means going back to that same old quest to find what works.

-The barrel may need cleaning.

-Lastly.......you may have a muzzle that needs recrowning.

Hope you find what the issue is.

[thekid]

My point wasn't to bash...but to state there are a ton of variables to consider.
Sometimes it is just not ONE thing but a combination of several coming together.

[Mr Sasquatch]

She can do rather well with the same support and hold. Here is 25 shots at 10m, the same bench, same AA pellets, but about two months ago and with the Leaper's scope.


or at 60 ft outdoors



What puzzles me is this regular up & down drift and almost no change in windage. If it was either the variation in pellets, hold sensitivity, bad seals, and/or shooter's error wouldn't the POI pattern be completely random?

Now, about re-crowning the muzzle... is this a DIY type of job or should it be left to professionals?

[Bullit]

With those shots, you need to start shooting our GTA contests.
Don't know if you golf or not, but alot of times a guy gets a new Driver or putter.  He has a great honeymoon...but then starts drifting back to where he was, with a little improvement.

[thekid]

Crowning problem, shotgun pattern.

Up and down, Generally seal or breach seal problem, or pellet size...inconsistent speed

Also as stated, very well could be the scope.
2 months ago, that was some sweet shooting!

[Mark 611]

here again Rob I agree with your view usually up and down string is either bad lock up, pellets or a seal issue but so is a lose or tight hold on the gun, I've noticed when scopes go bad the shots are all over the place in a shotgun pattern!

[jimmie lee]

My 34 will occasionally do what yours is doing...what I found to be the problem was me being inconsistent with hold. I use a sand bag at a table and when my groups started walking for no apparent reason I had to backtrack to find what I was doing differently and it boiled down to seating position and how I addressed the target and how I was holding the gun from the front to the rear. My worst shots came when resting the front of the gun on the bag instead of my hand and from not being totally into the shooting session. Takes a Zen approach and not being distracted, mentally, for me to have a great shooting session.