First bullet may be a 45-70 dating from about 1873. Or it could be a more modern muzzle loader one. Precise measurements of diameter length and weight would really help get a correct ID. Show a picture of the bases of both bullets please.
If my math is right the longer bullet would measure out to about a .38 caliber so it can't be a 45-70. That most likely means it is a modern bullet. It's funny that both bullets look to measure the same diameter but the shorter one looks smaller in the picture of the bases.
I'm am no means an expert but without proper measurements and weights it is difficult to determine. IMO these are post CW. I have a gallon jug of bullets that some I cannot identify because that are thousands of verities. Yes I would like to know more about the time period and types of bullets used..but unless you dedicate the time and research some are hard to determine..IMO
They are modern slugs and for future reference there were no conical bullets used in the 1700s, projectiles for firearms were pretty much round balls at that time.