Back in the 1980s we used to buy standard guns and chop off the barrels to 12.5 inch and recrown them .
This never effected the gun if owt the groups got better never bigger.
we used slide on silancers we did this on HW80s and HW77s.
we did this as there was no K guns at the time plus we wanted rid of the crimp end.
these 12.5 barrels shoot real good we used them on our FT guns at the time right till the end of 87 when we got pcp guns