Other How rare are the spring piston 10M airguns?

[beerthief]

Ha...that would be kind of a typical Mk 3! The gun is notorious for its huge transfer port diameter, which doesn't help. UK tuners sometimes sleeve it down to 3mm or so with good results.

Be sure the piston seal and tap are sealing well, and try different pellets. The traditional RWS designs - Hobby, Superdome, Meisterkugeln, Superpoint, Super H-Point - have really big skirt diameters which seal up nicely in the tap, and seem calmest in my .177 Mk 3's. To test sealing in any tap loader:

+ cock the gun
+ OPEN the tap (i.e., so the transfer port is blocked)
+ grasp the cocking lever...FIRMLY...!!
+ pull the trigger

If the piston seal and tap are doing their jobs, the lever shouldn't move very far, and will drift upward only slowly. But it can slam shut if things are loose.

it seems my seals are good to great . mine is a .22 BTW

 

[MDriskill]

That explains a lot! The Mk 3's .22 cal bore is slightly bigger than most. German guns are 5.5mm, older British guns are a true 22/100 of an inch, which math works out to 5.6mm.

Vintage Webley-brand pellets, or "blue tin" Eley Wasps, are true "5.6" ones, and highly prized for old .22 BSA's and Webleys. If you can't find those, a lot of UK shooters find the .22 RWS Superdome is is the best modern pellet for the Mk 3 (I guess RWS's .22 skirts run big, similar to their .177 ones?).

UK forums can be very helpful. Mk 3's are built like tanks and last forever, with the result you still see plenty of posts about them!