In at least a couple of cases we find ha;f-stocked guns listed in pre-Revolutionary War estate inventories in Lancaster County, as:
Henry Weaver. We have no evidence that Henry Weaver was a gunsmith. However, the two item inventory of the estate of "Henry Weaver, late of Lancaster County, Yeoman, deceased, dated 1 October 1774, showed 5 half-stock guns, valued at 26 shillings each, total £6/10/0; and 15 guns at 28 shillings each, for a total of £27/10/0. The half stock guns are unusual for the era. It is probable that he was an Indian trader.
Now in each case it is possible to read the inventoy as "only partially finished, half-stocked" or "made as half-stock long arms" Which is correct? The presence of many suggest, but does not prove, they were made as half-stock long arms.
Weaver's case is not singular or unique.
Most, say, pre-1830 rifles that are now half-stocks in my experience were cut down, perhaps after the fore-end was broken off the main stock. That is, most were made initially as full-socks.