Well, there is a Sheridan PG, which was the predecessor to the PGP. The last "P" in PGP stands for pump, remove that and you get...
Yep, the PG was a bolt action pistol. No pump arm needed since at the time you most likely weren't shooting at people with the thing, but marking trees to cut down or cattle to separate from the herd. Heck, the earliest version had the feed tube on the side of the gun. So pull back bolt, turn gun sideways to drop a ball into the breech, push bolt forward.
