Whisper Cat still under powered

[jonny75904]

It seems my whisper cat is still losing mojo, slowly but surely. I've reached out to Gamo on the issue.

I replaced the main spring and piston seal, cleaned the cylinder and put fresh molly and open gear lube in it. It's down to 593 ft/s at 15yards, using 10.5gr Crosman premiere magnum round domes.

One thing I think I may have neglected on - I did not have any silicone lubricant to put in front of the seal, but it's a synthetic seal so I don't think that could really be the source of trouble.

I'm wondering if the problem could be in the breach? It doesn't look user serviceable though, so, I don't really know anymore...

 

[Deja]

to much lube in the piston chamber? that might slow it down

 

[JohnL57]

Might be the piston seal is too tight.

 

[Windmill01]

Or opposite to John the seal may be too small. Did you notice when you replaced the seal was the piston easy or hard to slide down the chamber?

 

[jonny75904]

It wasn't terribly easy. I tried to take it easy on the molly, covering the sides of the cylinder thoroughly but wiping on the excess before it went into the cleaned tube. I was heavy on the spring's open gear lube, and no silicone between the cylinder and breach.

 

[JohnL57]

The only other thing I can think of is the breech seal- put a piece of tissue paper on top of the breech where it meets the barrel and fire a pellet. See if the paper blows up indicating a bad breech seal.

 

[Windmill01]

If it's not the problem that John mentioned about the breach seal I would strip it down again. You only need a very small amount of molly on the piston. The first time you fire it the molly will go everywhere. As for the gear lube I would clean most of that off as well. Deja might be correct, as too much lube could be restricting the spring movement. I was told along time ago that applying extra lube on the spring quietens it down but have never tried this. Throughly clean out the chamber again and apply a very small amount of silicone to the sides of the seal, not in front. Where I buy my seals from the chap impregnates the seals with molly so no need for silicone. If that fails it maybe the spring itself. Good luck.

 

[jonny75904]

Any particular solvent I should / could use for the molly and OGL? Or is a dry paper towel preferred?

 

[Windmill01]

When I strip down an air rifle for the first I use a small file to remove any sharp edges at the beginning of the chamber and the cocking slot etc that may damage your new seal when it goes back in. You have to make sure you remove all the filings when you clean it.
You can use a degreaser in your chamber and on the spring but make sure you remove all of the degreaser and it's dry when finished. I have tried both degreaser and paper towel, and prefer the paper towel. To clean out the chamber I use a couple of paper towels wrapped and taped to the end of a dowel rod with a split in one end to help secure the towel. I do this several times to ensure the chamber is perfectly clean.
Use your finger to put a very small smear of silicone oil around the edge of your seal making sure you get none on the front of the seal and that there is no molly or lube in your clean chamber when you insert the piston. 
Do you know what Gamo rated the fps on your rifle? If this doesn't work you may have to get a higher rated spring or a gas ram. Good luck.