Diana 350 Issues

[mac1029]

Got a question for all the gurus out there, back story my D350 has always been a tack driver (1/2" Groups at 35 yards) i have the Vortek PG3 installed for sometime now, and have a UTG 4-12 Compact scope on top. I was shooting today and she was dead on untill i got a flier so i thought, then at times i can get 2 shots pellet on pellet too one 2 inches high too a couple 2 inches low. i rest for a minute and shoot and dead on again. It does have a fairly new (1 month ) Vortek seal in it. Does this sound like a seal? Or could it be the scope, which i doubt as it keeps returning to POI.

UPDATE so since my POI is vertical i pulled the breach seal and put some dental floss under it as it already has 1 shim underneath. shot a 10 round string and still running up and down. Looks like i will order a new seal and breach seal as well

[mpbby]

If you shoot at a chrony, it acts as a probe about the spring and seals possible issues.  As a rule of thumb, if the ‘Extreme Spread’ (ES = max FPS minus min FPS) is bigger than 4% of the average FPS, you usually should disassemble to check the parts.  The Chinese chrony at aliexpress did fine with me; you can research something as “muzzle velocity meter”.

In order to assure the locking up returns to the very same position, I stopped using dental floss.  So, only that one OEM shim, and I think is fine for sealing.

Troubleshooting inconsistency, and during several years, the scopes on my D 350 were just one more suspect among the others..  I assume that every scope has a lifespan on a springer, even more when on a D 350.  At the end of the lifespan, it stop holding adjustments. So, nowadays, no matter if POI is changing for good or “come and go”, I do a focused scope test on the D 350.

 https://www.gatewaytoairguns.org/GTA/index.php?topic=169344.0

If you have any questions about the test, I may try to answer.

[DanD]

As far as breech seal shimming, sometimes too thick a seal causes stringing because there is too much cushion for the barrel to close in a consistent place.
You could try swapping scopes with another gun to test the scope. You don't need to zero the swapped scope,  just aim at one spot and shoot a group wherever it lands.
If both scopes string,  you could try shooting  with iron sights and see if that makes a difference.
Good luck!

[WHITEFANG]

Vertical stringing is a sign of lock up issues and or as mentioned power plant issues. Indeed the chrony should help you on the power plant.
We also need to test another pellet. As mention no scope adj on testing and just aim at the same point. If a mil dot scope learn to dope the scope before making scope adj. If not you will be chasing the scope adj all day. For many the D350 can eat scopes all depending on the build and scope mount. I personally used the droop mound that came with the guns. I lost few UTG scopes on any of my many D350 GUNS which were all built to aftermarket magnum power.

Not that this will help stringing but check the barrel pivot tightness as well. Most D350 guns even when new needed the breech seal shimmed. Diana has Factory shims for all their guns for a reason. Some factory guns have the seals shimmed. Your method of shimming will work but even a pop can shim is better fitted vs the floss. The floss some times bunches up and the does not allow the seal to be the same height all around. This can cause issues.

On another note I would check the scope for optimum center or at the least make sure you are not close to the max on adj if not using a drooper mount. You may be bouncing near the limit of the elevation adj.

Another thing is to look at the barrel block upper area and the tube contact. Look to see if the 2 surfaces are making contact. If they are you will see wear marking. The angle barrel block is known to contact on the top area I have mentioned. This can be and indication of a seal fit issue but can be just the machining. This area can be filed off being careful and reduce droop and help sealing also. You can expect a slight wear indication but none is better. Also look at the TP sealing area for a good clean circle where the seal is sealing. You may have to clean the surface off if you replace the seal to get another indication of the new seal.

As I have shared there can be several check points in your issue. The chrony is a great tool to standoff with when trouble shooting any airgun. AJMO I was at one time a huge Diana fan and there is still not issue for me with the Diana line. Just not sure of all the newer one's?

[dtdtdtdt]

Is this with a new tin of pellets???

When I was getting anal about pellet weight I bought a scale that would differentiate 0.02gr (0.001gm). I found a spread of pellet weights of nearly a grain in a tin of supposedly good pellets.  I separated some in .02gr incremental batches and shot them as separate groups.  I saw vertical stringing of about 0.5" at 20yds.  Not enough to be really noticable in most shooting but enough to annoy me.

If a well-known batch of pellets - forget what I just said but keep an eye out for unexplained stringing. 

Scopes could easily be the problem.  Try another if you have one available. 

Inconsistency in hold???

Cheers and good luck.

[HectorMedina]

Mac;

If the dispersion is PURELY vertical, then either you or the gun are not locking up consistently.

Powerplant problems always bring dispersions in all directions, MAYBE it is predominantly vertical (ranges in excess of 25 yards), but if your dispersion is purely vertical, then it is most probably a lock-up problem.

It is important to understand how the OEM ORing seal in the breech of the 350 works, and it is somewhat counterintuitive, but there is a simple test that you can perform with a "loose" Oring seal to demonstrate this:

With an UNLOADED and UNCOCKED gun, if the safety is on, put it off and pull the trigger. If noting happens, then you can proceed with the test:

Blow with ALL your lung power into the barrel. If you can feel air escape, then you need to replace the ORing. But you should replace the ORing with the same size and durometer rating as the one used (65-70 ShA).
Vortek seals, and some other brands, that are more like squat cylinders, try to seal with the closing pressure, not with the air pressure of the shot itself.

You say you are using a Vortek seal, but you are not clear of it is a breech seal or if it is a piston seal.

IMHE, Vortek breech seals enhance the droop, increase the inconsistency of the lockup and create more problems than they solve.

But, that is JMHO.

Good luck!






HM

[WHITEFANG]

Stringing is pretty self explanatory but here are pic's of both examples.

Many things can affect this either directions. And the shooter is just 1 factor among many other things. Plenty of info on the GTA 😁 n this topic in the past. The search engine is your friend.
Very broad subject💀 As always JMO💀

[mac1029]

Thanks everyone. I do have a Chrony and will be out to better diagnose it today. When i installed the Vortek PG3 kit i also installed a Vortek Piston seal, it is one of their new ones with moly impregnated into it. I will say i have 1000s of rounds through this rifle and do know for sure the stringing was definitely not shooter error.I do have a drooper mount on top and the rifle locks up tight as she should and my tension on the pivot screw is correct where it just holds the barrel weight from falling. I will also try the blow test down the barrel as indicated above. Now i did notice a week ago when shooting that the cycle did seem off at times where my thump sounded and felt at times different like weaker. So the chrony will telkl me later. And i also have other scopes mounted to other rifles i can swap on to see it it is scope related.Thanks for all the replies i did order some new seals.

[mac1029]

Well its safe to say its a piston seal my D350 shoots Jsb 18.13 on average 780 FPS, Today i was getting a deviation between some shots of 50-65 fpsand when i did, thats when i was stringing low....

[Yogi]

Thanks everyone. I do have a Chrony and will be out to better diagnose it today. When i installed the Vortek PG3 kit i also installed a Vortek Piston seal, it is one of their new ones with moly impregnated into it. I will say i have 1000s of rounds through this rifle and do know for sure the stringing was definitely not shooter error.I do have a drooper mount on top and the rifle locks up tight as she should and my tension on the pivot screw is correct where it just holds the barrel weight from falling. I will also try the blow test down the barrel as indicated above. Now i did notice a week ago when shooting that the cycle did seem off at times where my thump sounded and felt at times different like weaker. So the chrony will telkl me later. And i also have other scopes mounted to other rifles i can swap on to see it it is scope related.Thanks for all the replies i did order some new seals.

Bummer, those Moly impregnated seals are supposed to be good.

-Y

[mac1029]

Thanks everyone. I do have a Chrony and will be out to better diagnose it today. When i installed the Vortek PG3 kit i also installed a Vortek Piston seal, it is one of their new ones with moly impregnated into it. I will say i have 1000s of rounds through this rifle and do know for sure the stringing was definitely not shooter error.I do have a drooper mount on top and the rifle locks up tight as she should and my tension on the pivot screw is correct where it just holds the barrel weight from falling. I will also try the blow test down the barrel as indicated above. Now i did notice a week ago when shooting that the cycle did seem off at times where my thump sounded and felt at times different like weaker. So the chrony will telkl me later. And i also have other scopes mounted to other rifles i can swap on to see it it is scope related.Thanks for all the replies i did order some new seals.

Bummer, those Moly impregnated seals are supposed to be good.

-Y

I will update my findings when i open her up in the next couple of days.

[mpbby]

Well its safe to say its a piston seal my D350 shoots Jsb 18.13 on average 780 FPS, Today i was getting a deviation between some shots of 50-65 fpsand when i did, thats when i was stringing low....

If you deal with ChairGun, there is a tool 'vertical stringing' to know how much difference in FPS makes what vertical difference to POI.