The RN had a few brass sea service 3-pdrs during the 18th century. These were 4.5 feet in length and weighed 5.5 cwt. The RN considered the 1-pdr swivel to be too cumbersome and relied on the ½-pdr.
Even if we are talking Swedish pounds, the 2-pdr would still have been about 1.85 British pounds – possible for a swivel but awkward to handle. I think that I recall seeing a design of Chapman's for mounting heavy swivels and are perhaps those in Jenku's post of 2nd March, 2009:
Perhaps Jenku can assist, although I do not recall his mentioning the size of the swivels on board Gunboat N. 14, and see