Shooting Low/Left after tuning

[davhowrd]

Hello Team,

I have 2 BT65 25 cal rifles and I just completed a tune on both. The first one is a Tack Driving BEAST, but the second is hitting hard left and low. I first thought that it was the scope going out because it ran out of adjustments; what I thought was too early. Swapped out scopes and there was no change in the POA. It's hitting consistently, dead-on, just low and left. I've checked the seals, mounts, screws, and scopes; no luck. Either I missed something or there's a issue that I haven't seen. Please advise, Help is Greatly Needed.

 

[TNT19]

Did you mess the barrel in any way shape or form? And did you check the mag to make sure it's not clipping the pellet, or the pellet probe?

 

[davhowrd]

The barrel swap was so that I could try shooting slugs with a fresh barrel, but I can't even get it to shoot the JSB's correctly. The mags are good and the probe is perfect. I've swapped back to the original barrel and I'm getting the same results. I am at a complete loss.

 

[bubblerboy64]

I don’t know if this will be a help or not . I’ve been working with my impact MK II and every change while tuning meaning regulator pressure, hammer spring tension and valve adjustment changes the velocity and also the POI .

I believe this is due to barrel harmonics 

I have noticed the same while working up loads for powder burners.

 

[shambozzie]

Try adjusting pellet speed +/- 10 fps increments and note poi change. Bubblerboy64 spot on about barrel harmonics.. Hope u figure it out soon.

 

[davhowrd]

With every thing that I've checked and reviewed, then double checked; I'm beginning to thing that the transport seals aren't holding. I've swapped scopes, changed air tubes, tried different mags, and still hits in the same low left. I will say that's it consistent and very accurate, just far off to the low left beyond the scopes ability.

 

[bubblerboy64]

Ok. I AND MAYBE WE. did not understand. You are saying the gun is shooting. WAY Off Clearly there is a mechanical problem . I must say it does seem strange that it’s shooting accurately just way low and left My wild guess is the barrel isn’t pointed in the right direction or it’s bent. . Can you remove the barrel and roll in on a flat surface Has the barrel even been off the gun? Was the gun dropped or out of you direct control? Almost has to be barrel alignment.

 

[Keyman62421]

R grub screws on the mark? Slight twist or in and out could cause barrel slant. Can you look through mtg screw holes and make sure you're aligned. Just a thought.

 

[elh0102]

If you are getting the same POI with both barrels, but consistent groups, and you have ruled out the scope, then it seems to me the issue has to be either the scope or barrel attachment points. Maybe try replacing or reversing the rings.

 

[Airgun-hobbyist]

On that particular unit, can the barrel/liner be indexed (rotated)? If so, maybe try indexing the barrel for the best group and then sight it in with the scope.

 

[davhowrd]

Dear Team, I want to thank everyone for their advice and comments. I've come to the point of ordering a new upper section because there is nothing that I can think of that would cause this issue. I've triple checked both barrels, replaced out the breech seal, barrel seal, transport seals, and even changed the seals on the air tube; all with no change in the POI. This rifle was a tack driver prior to the barrel removal, but even after re-installation it still hits to the low left. 

 

[davhowrd]

Team, 

Once the new part comes in, I'll keep you posted. It's really mind boggling, the rifle is accurate and super consistent; with the only flaw of hit low/left beyond any corrections. I'll keep you posted. Thanks again for your inputs.