Quote Originally Posted by pelletcaster View Post
HW35's are something special on their own.
Mine was my very first AG and the one I started fettling with many years after the purchase.
Still love it.

One thing you should know:
Simultaneously to the introduction of the HW77 in 1980 the HW35 design was changed from leather to synthetic piston seal (from ser.no. 843636 on).

The transfer port size of the leather seal models was about 4,2 mm.
If nowadays you like to switch such an old system to a synthetic seal, easy-peasy with an adapter, the TP-size should consequently be reduced to about 3,0 mm.

Easily done by gluing in a brass tube like the ones available here:
http://wasana-airgun-tuning.de/shop/sonstiges/
Please scroll down little bit to:
Messingröhrchen 4 x 0,5 x 30mm für HW35 alt
I think that is correct on the 35 TPs and seals.

On a point of detail, the 77 came out in 1984. The 35 TP/seal change happened earlier and independently of changes to the 35.