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Teriyaki_Man

Mysterious Holes

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Anyone have an explanation for the mysterious holes in the crown of my Airsporter Mk6 piston? Could it be extreme dieseling?

 

I would add that I just bought this as a restoration project so it wasn't me that let the old girl get in this state!

 

Also, the replacement piston is different with the seal down near the skirt rather than up by the crown. Anyone know if the pistons are compatible?

 

Cheers.

 

post-32918-13951751747_thumb.jpgpost-32918-139517519079_thumb.jpg

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Guest raygun

I can't see dieseling causing that damage. It does look like something has found it's way into the cylinder and has impacted the piston head a few times. (perhaps a BB)

 

The new piston head will work but you will also have a greater volume of compressed air at a lower pressure. Your swept volume will decrease slightly whilst your compression volume will increase. This will result in lower power, all things being equal. You could pack the spring to try and counter that.

 

ATB

Ray

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I agree with Ray...I bet it's a .22 Cal. & someone has introduced a .177 steel BB into the tap & it rolled back into the cylinder.Both those piston heads are okay..the steel one is the upgraded version with the fixing pin hole in the recess where the O ring fits...the old alloy dented one is the standard production one..the replacement steel one is heavier & acts like a piston weight too..hope this helps.

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I thought you had it there, until I tried a .177 BB for size - it's too big. Also, the holes are different sizes!

 

My latest theory is bubbles in the alloy during manufacturing. It's the best I can come up with!

 

The mystery continues.

 

Thanks for the info on the new piston. I'll post some pics when the restoration's finished. I always find BSA's re-blue really well with BC blue.

 

post-32918-139526765659_thumb.jpgpost-32918-139526767981_thumb.jpg

Edited by Teriyaki_Man

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Definately caused by a ball bearing, not necessarily a .177bb. Possibly the bb that acts as a detent for the loading tap index plate.

Pete.

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Definately caused by a ball bearing, not necessarily a .177bb. Possibly the bb that acts as a detent for the loading tap index plate.

Pete.

 

Think you have it there Pete..after a loading tap out moment..then it's been "shot out" when the rifle was cocked/loaded & pointed downwards before firing it..bet it's been done before too.. :rofl2:

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Its a series of drill holes done by some monkey, you can even see a centre punch mark.

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Think you have it there Pete..after a loading tap out moment..then it's been "shot out" when the rifle was cocked/loaded & pointed downwards before firing it..bet it's been done before too.. :rofl2:

Yes Chris, ask me how I know this.?.....lol.

Pete.

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Yes Chris, ask me how I know this.?.....lol.

Pete.

 

Could be worse Pete...the spring & ball could have been in there...!

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Reminded me of an old air rifle that was given to me as it didn't work. It had ten .22 darts jammed nose to tail in the barrel!

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That's what a 1/8 inch piece of drill rod and a sledgehammer are for!

Actually, I found something that works really well for a jammed .177 that is jammed bad.

Take some brass or alumnium nails(they won't mess up the bore, but steel will) and cut off the heads and points. The longer the nails the better...

Get the barrel full of them. just clamp the gun in the vice by the barrel, and gently tap the nail sticking out of the barrel with a hammer. GENTLY.

It works wonders when some idiot loaded 8 pellets at once into a crosman 1377.

Another one is to use the vice itself to push out the pellets, Doesn't do the damage a hammer would to the gun.

It requires a big vice(I have a woodworker's vice that opens to 36")

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Are you still in feet & inch's over there...bless...we had to conform (go metric) to the rest of Europe years ago..!

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Just spotted the heading on this post.

Not what I thought it would be, Forget it! :poster_oops:

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Haaaaa Ha...this is an airgun related "hole" Pete...I think you need a different web site..

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