Crossbows are legal for elk. See pages 20 (bottom right) and 21 (top left) of the 23-24 digest.

https://www.pgc.pa.gov/HuntTrap/Law/Documents/2023-24%20Digest%20lowres.pdf

Elk Season
• Manually operated centerfire rifles and handguns at least 26
caliber using all-lead projectiles or bullets of at least 120 grains
designed to expand on impact;
• Manually operated or semiautomatic centerfire shotguns
(shotguns do not have to be plugged) that propel single-
projectile ammunition. Shotguns must be at least 12-gauge;
• Muzzleloading firearms (including handguns) at least 50 caliber
propelling a single projectile weighing at least 210 grains

Elk Season (continued)
• Bow with a minimum draw weight of 45 pounds;
• Crossbows with a minimum draw weight of 125 pounds
• Any arrow or crossbow bolt with a broadhead that has an
outside diameter or width of at least 1 inch, and the length may
not exceed 3.25 inches.
• See Elk Section for dual-carry sporting implements rules when
hunting elk.

 

Thank you

 

using all-lead projectiles or bullets of at least 120 grains -

Does that mean that copper jacketed bullets are illegal ?

Also what is the difference between a projectile and a bullet ?

 

Jacketed expanding bullets at least 120 grains are legal

 

Shotguns can have a single projectile or multiple projectiles and neither are called bullets.Rifles and handguns shoot bullets.