Airsporter piston jammed ?

[wints]

The piston can jam through a couple of reasons. The nylon piston head can absorb moisture over a period of time and swell in diameter. Also the piston buffer washer can disintegrate and become all gooey through bacteria. There are a number of methods for getting the piston out. I use brute force with a hammer and drift on the piston cocking slot. Others use chemicals and heat. I skim the piston head down and refit it, and make a new buffer washer.

Baz

That appears to be a common theme running through the posts I've read through. I'm trying to get my head around the tricky bit of getting the trigger assembly (I think that's what it's called) off the gun.

Allen

[Benelli B76]

That appears to be a common theme running through the posts I've read through. I'm trying to get my head around the tricky bit of getting the trigger assembly (I think that's what it's called) off the gun.

Allen

I have done a lot of these in the last few months. The trigger assembly usually comes off easily in 80% of the cases but you can get some very tight ones. Disconnect the cocking lever linkage to the trigger block so it is free to unscrew from the compression tube. Try and unscrew it using a bit of leverage through the aperture where the trigger and sear are pinned, you may have to give the lever a few taps with a hammer to shock it free. If it does not shift you may have to apply a little heat to the steel compression tube. Also use any type of penetrating spray oil you may have. As you unscrew be careful of spring tension being released.

Baz

[Airsporter1st]

I have done a lot of these in the last few months. The trigger assembly usually comes off easily in 80% of the cases but you can get some very tight ones. Disconnect the cocking lever linkage to the trigger block so it is free to unscrew from the compression tube. Try and unscrew it using a bit of leverage through the aperture where the trigger and sear are pinned, you may have to give the lever a few taps with a hammer to shock it free. If it does not shift you may have to apply a little heat to the steel compression tube. Also use any type of penetrating spray oil you may have. As you unscrew be careful of spring tension being released.

Baz

That will work, but its better to use a suitable lever through the round hole in the block, just forward of the trigger/sear apperture, which is provided for the specific purpose - much less risk of damaging the trigger assembly.

[SRV1]

Wints/dalesman917 - same here on a Mercury Mk1. Rather than face the same effort of a repeat job in future, I didn't bother to skim the head in the lathe, I replaced it with aluminium head. My Mk1 which I bought very cheap, was in very good condition externaly and no slop in the breech jaws and curiuosly, it is very consistent and very accurate since the rebuild - I was going to sell it on, but, I'm keeping it!

Meant to have added, used a Meteor O-ring: 3/4" X 1/8"......

[Benelli B76]

Once the nylon has been "water conditioned" it will not swell any further in future. Nylon products that have to work to close tolerances should be water treated before final sizing. This apparently was not carried out by BSA hence the legacy of seized piston heads

Baz

[look no hands]

This is why I always recommend stripping down any Airsporter or Mercury as soon as you get it to see what condition the innards are in, I do it every time with mine, for the sake of £20/30 it save a hell of a lot of aggro trying to remedy it when it's jammed up.

Pete