What the heck is going on with my accuracy? PLEASE HELP!

[sawtoothscream]

same with my benjamin trail i had. almost 600 pellets and the groups never got better, they actually got worse. tried different scopes, holds the GRT III trigger ect... gun was just horrible. i sent it back for a refund and got away from springers.   good luck getting it to work out for ya

[condornh]

I'm going to throw out a wild idea and see if it makes sense:
As the piston starts to wear in or it has been cleaned and lubed, piston speed picks up. There is very little distance between the end of the piston anvil and the compression tube. If you look real close under magnification, you may see a slight polish mark that looks somewhat like the port or part of it.
What may be happening is the air bubble is collapsing a little too fast as the pellet starts moving allowing the piston end to crush the seal enough to touch the compression tube end cap.
That sporadic touch at the wrong time could cause harmonics that will disturb the pellet flight ever so slightly.
If you see that polish mark (not an indent as it is not hitting that hard), then grind off a 1/32 inch of the anvil and see what happens.
I actually know of a case where doing such brought groups from a quarter touching to a dime covered.

[dkwflight]

Hi  order up some heavy pellets 13 15 grain for the .177
My titan GP likes the heavier pellets.

Dennis

[z28rod]

artillery hold

[CharlieDaTuna]

The piston never actually "wears in" because for the most part, it just floats in the chamber and makes very little contact with the cylinder walls in. Certainly not enough to negate any movement of the piston 

Not sure what an "air bubble" is but I never saw one in all my years of tuning.

The seal always makes contact (and should) with/at the bottom of the cylinder and act somewhat as a cushion. Otherwise you would have a constant slamming of steel (can you imagine the shock that would create)   into steel as the piston reached home. Many guns use seals (like an FWB and many of the older Chinese B-xx models for example) that have a synthetic solid surface face seal also. Many leather seals are solid faced. You definitely want something between the bottom of the chamber and piston in most guns using that type of power plant.

Eight or ten years ago when the early B-21's (The Beast) were popular you could always tell when the seal was cooked, hard as a rock and burned away in places. A popular occurance back then. Every time that you shot it, and that piston slammed home, it would just about jump out of your hands if you weren't hanging on to it and if you hung on too tight, you had to count your teeth to see if you still had them all.

Just thoughts

CDT

[randomgunner]

i get the hold sesitivity thing, but, the gun is a nitro piston. it uses nitrogen to fire, so why cant heavy (.22: 18 to 20 grains) pellets be used?

[bradyman1]

I think the air bubble that air gunner was talking about is the column of air that the piston pushes the pellet out with?

[CharlieDaTuna]

It's not a question of Nitrogen or air. That in itself makes no difference. It's the type of power plant that is important. Springers can be very pellet weight sensitive where spring damage is a matter of  concern. A ram can use heavier pellets but only up to a point where the pellet weight is counter productive.