GTA
All Springer/NP/PCP Air Gun Discussion General => European/Asian Air Gun Gates => UK Airgun Gate => Topic started by: happymecanic on November 02, 2022, 10:01:50 AM
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Is the piston rubber buffer washer really necessary on the piston?
I need to rebuild the piston head on my Scorpion (have all the new parts), which has an almost seized-up buffer washer, and was wondering if I could replace the rubber washer by a washer made from something else, like teflon or UHMW. Would these materials be too hard? I'd love to avoid having the piston seize again in the future. TIA.
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Nevermind the questions, I found out:
https://www.airgunbbs.com/showthread.php?715447-BSA-Scorpion-cheese-buffer (https://www.airgunbbs.com/showthread.php?715447-BSA-Scorpion-cheese-buffer)
https://www.airgunbbs.com/showthread.php?857083-BSA-Scorpion-pistol-technical-info-and-history (https://www.airgunbbs.com/showthread.php?857083-BSA-Scorpion-pistol-technical-info-and-history)
As I suspected, the buffer washer was dried out and seized, I had to hammer-out the piston with an aluminum rod. The buffer crumbled into dust as soon as I started to move the piston. Fortunately I have the replacement parts, but I may make a buffer washer out of leather instead of using the urethane (?) one in the kit. Leather doesn't seize and can easily be rejuvenated if needed. Also found out I had plenty of replacement Orings (1 1/8'' x 1/8'') in my ''universal'' Oring kit. Only the breech seal is a proprietary item.
BTW a Diana 28 mm seal is said to fit in the compression tube when the correct adapter is used. One must keep in mind that the seal ''installed height'' must be the same as original, otherwise there can be an interference with the sear if the piston goes too far forward.
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T. R. Robb in UK has some interesting suggestions for the Scorpions. The site is a little different to navigate
https://www.trrobb.com/BSA_Scorpion_adjustable_modified_SS_piston_head/p1449438_15951502.asp (https://www.trrobb.com/BSA_Scorpion_adjustable_modified_SS_piston_head/p1449438_15951502.asp)
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T. R. Robb in UK has some interesting suggestions for the Scorpions. The site is a little different to navigate
https://www.trrobb.com/BSA_Scorpion_adjustable_modified_SS_piston_head/p1449438_15951502.asp (https://www.trrobb.com/BSA_Scorpion_adjustable_modified_SS_piston_head/p1449438_15951502.asp)
Thanks for the link, that's good reading!
I decided to use the urethane buffer washer, along with an Oring from my kit. I also had to use a 1 mm (0.040'') thick spacer washer, not provided in the rebuild kit. I also took the opportunity to deburr the TP inside the comp. chamber, as you can see in the pics it left its mark on the piston head. I used a brand new main spring, had the ends polished and squared, the spring guide and spring were dry-tungsten burnished and the gun re-assembled with a cleaned-up and re-lubed trigger group.
Shot cycle is nice, albeit a bit snappy, the new main spring needs to set. First chrony shot with a JSB Exact Jumbo 15.89 grains pellet showed a velocity of 422 fps, with no dieseling. That's 6.28 fpe, not bad for a 50-years old pistol, I now SEE why they were re-called in the beginning ;D (mine's an early Mk1 version).