Quote Originally Posted by Phil Russell View Post
I post this just in case ... it is from my notes and was put on here some time ago:
NOTES ON THE HW77 SAFETY CATCH AND SOME BOLT SIZES
I post this in the hope it may be of use to someone as the safety pin and trigger housing tang crops up from time to time. The notes are ones I compiled for my own file but I cannot guarantee they solve all trigger issues:
Some time ago I bought a s/h MK1 (c. 1984, no abt) HW77 in .22. Nothing special but the price was cheap, although I can’t remember how much. It shot quite well but I had noticed a need to overcome some roughness/notchiness at the end of the cocking stroke. The safety worked OK.
But today I thought I would have a look and trace this notchiness as it should not be there… a click as the latch rod engages and the safety pops into action is OK but notchiness, no.
An initial strip gave no obvious clues although the safety pin spring was deformed and looked like a home made crude replacement. I found a suitable new one. There is no anti-bear trap on this 1984 MK1 vintage. I removed the mainspring, pleased to see it was in good condition, as was piston and seal. I rebuilt the action minus the mainspring and set it in a vice to watch the cocking action. All was smooth except at the end of the cocking stroke where an extra tug was needed to set the trigger and safety. Out came the trigger block again and I reassembled without the safety pin… no notchiness, very smooth. So the issue was the safety. There was nothing wrong with the pin and the new spring and it moved smoothly in the cylinder. So … to the trigger. I noticed that the tang in the trigger housing that engages with the safety pin was somewhat deformed and the c. 6mm deep x 2mm wide slot visible in the trigger frame was certainly bent out of true; wider at the open top than down into the frame itself. With the aid of a small vice I straightened the slot and using pliers, bent the tang back into shape. There were some score marks on the tang which I smoothed out with a file. On cocking the trigger manually I could now see the tang was about 0.5mm away from the side of the rear sear whereas before it was just clearing the sear on cocking.
On replacing the trigger housing with the safety pin in place but minus mainspring, the cocking cycle was as it should be, smooth and the safety pin worked as it should with the trigger releasing the latch rod. Reassembly with mainspring followed and some test shots fired. Excellent result; notchiness gone, all smooth.
My conclusion is that at some point there was interference between the safety pin and rear sear during the cocking action, possibly due to the naff safety pin spring. This led to increased force being needed to cock the action which in turn led to deformity of the tang which made the situation worse … etc etc.
While doing this I took a few measurements that may be of interest:
The Safety Pin: Overall is 33.95mm long. Working from the thin pin end:
This thin indicator end is 2.9mm diameter x 9mm long (can be longer, but not shorter)
The centre barrel is 6.95mm long x 5.9mm diameter
The centre thin section is 5mm long x 2.45mm diameter
The end you push is 13mm long (can be longer but not shorter) x 5.9mm diameter
The hole in the action for the ‘push’ is 6mm.
Screw sizes: Forend stock screws M5 thread x 12mm pan head slotted
Front trigger guard M7 x 30mm pan head
Rear trigger guard M4 x 10mm cnsk

Cheers, Phil
thanks Phil for that I’m going to have another look later today mate