TargetTalk

Hi All,
Hopefully someone can help me out here. Our team has two Daisy Avanti 853s that shoot fine up until 30-50 shots have been taken. Then we start getting occasional weak shots - they sound funny, and the pellet hits way low. I have used a chronograph to check, and I'm seeing some pretty large variations in speed (>50 fps) when this is happening. This is in a rifle that has less than 10 fps variation at the start of shooting. We are using Champions Choice competition pellets. I have replaced all of the o-rings, valve seal, wipers, etc. and inspected all of the seats. The air plugs are tight. I can't find anything to even give me a suspicion of a problem. These rifles are of unknown vintage; they were donated to the program, so I don't know their history as far as work that was done on them. Other than getting new rifles (I wish we could!), does anyone have any suggestions or have you experienced anything similar?
Thanks,
Mike

Coach - Washington MO JROTC rifle team

Well here is a dumb question, have you oiled them up lately? A lack of oil on the felt can cause erratic velocities and loss of velocity.

Jimro

Not so dumb! But yes, they are well-oiled. This seems (to me, at least) to potentially be a problem with some part warming up from the compression since it consistently occurs during a session after about 30 shots. I inspected everything I could get a look at with them completely disassembled, looking for cracks,etc. Nothing visible. It may be some parts are out of spec, but I don't know what the specs are to measure them. They have had less than 500 shots through them since I replaced all of the packings, valve, etc. The air tubes are in good shape, too.
Thanks,
Mike

If it is a case of leakage due to heat, there is nothing to do but begin "diagnosis by replacement."

Since both rifles do this, I'd say that the odds are that it is the same problem with both.

Things I would try.

On the assumption that you did the trigger mod, set the trigger to a higher trigger pull and shoot 40 shots as rapidly as possible to see if the trigger group might be involved, if things are heating up and the trigger isn't providing enough resistance I could see it being a source for a leak. If increasing the trigger weight changes nothing or changes something, it's a clue either way.

Next up I'd order two more rebuild kits, but have someone else mechanically inclined do the work. Not saying it's your fault, just saying that having someone else do the work is way to eliminate the mechanic from the problem. If something changes, or nothing changes, either way, it's a clue.

Last up, if all else fails, try replacing the oil for new felts with some silicone grease. It might be thick enough to plug up whatever small leak is the problem, at least for enough shots to be useful for a junior shooter.

Wish I could be more helpful,

Jimro