I had a mk1 when they were first released.
I remember I had a choice of the hw77k or the new bsa.
After much handling shouldering in the shop I plumped for the bsa. Reason I think at the time was it was lighter than the 77 and I liked the loading port.
It was super accurate, nice trigger and accounted for a great number of rabbits ,)
Think I had it for a few years then traded it for a hw80.