SPA 700 PCP Pistol Discharge Air "Blow-by"...

[Hepotter]

I've been trying to quiet my SPA down as much as possible to avoid my Commie neighbors from calling the PCP police.

I finally found the problem with that annoying "Blaaaat" sound when I shoot the gun. I put a DonnyFL Tanto on it and the gun was immediately much much quieter...but, that "Blaaaat" noise was still there.

I finally associated it with the occasional blast of air on my face....it was coming past the O-ring around the transfer port/loading block. I realized the only thing containing the airflow from the air cylinder to the pellet was the tilting transfer port/block that covers the pellet when you load it. Only the O-ring stops air from escaping the gun near your face.

I examined the O-ring and it was dry and "flattened". E\

I replaced the O-ring, and lubed up the new one with silicone grease and sure enough the air blast stopped and the noise was gone. I don't see any way to tighten that block at first glance. If it loosens, it will be a problem, but so far so good. I did have to grind the handle slot down an 1/8" or so to permit the block to drop all the way down to get the O-ring out, thanks to the forum member who posted that mod some months ago!!!

If anyone finds a better solution, let me know. I tried one size thicker O-ring but then the block wouldn't close...oh well. Still a neat as hell well built little pistol/carbine!





Kinldy 'Ol Uncle 



",,,I've always said that boy's dumber than a damn rock!!!"

 

[nervoustrig]

Yes mine was a loose fit from day one. Replaced the OEM metric O-ring with the nearest fit “dash” (inch) O-ring. The extra 0.011” thickness made all the difference and it has held up great for about 4000 pellets so far and is still snug when closing the block.

 

[Motorhead]

When these pistols first came out had done a Complete forum article over on the GTA. Within it was a few tricks on machining a new breech end thimble or if re-barreling where a big fat HW spring gun breech seal could be fitted.



That mod is AWESOME being the HW seal has more area and yields some so a good seal can be made. + it don't wear out either being urethane.

 

[DirtyDovi]

O-ring Issues:

Yup, I experienced the same thing [oddly enough] with both of my Artemis guns.. 
The PP700 and the P15 both gave a burst of air back towards my face - enough to make me flinch.. 
I can't remember which was which, but, 1 needed an o-ring replaced, and the other just re-seated. 

Quick fix in my case, and both have been working flawlessly since then [day one]

 

Sam -

 

[bandg]

I used a piece of nylon pipe from home depot to make a new breech end piece that allowed use of a very fat o-ring from barrel wall to bore wall of frame and have no blowby since fitting that arrangement. If one has the equipment to fit the HW seal that would probably be better but the fat o-ring has worked fine for mine. I did it with a drill press, a dremel, a tap to match barrel threads, and simple hand tools so most could do it also.

 

[barreira]

Hi all,

I already sold mine, but before that I developed a kind of carbine breech that works a treat:

 

[barreira]

One more:

 

[DirtyDovi]

barreira,

Fantastic fabrication and machine job!
Your setup looks awesome! Very nicely done!

 

Sam -