Depends on your definition of improvement. I shoot both lead and copper in my Pulsar and R10Se. Chrony about the same and group about the same. Game deeper penetration the copper is better. For expansion, lead is better. This is just my experience. It may be much different for others with different weapons.
Some packages of the Crosman Copper Magnum state the weight as 15.9gr — which is an error, they are 14.4 grainers, just like the Amazon link in the OP says.
If you like to try other copper pellets (that are less expensive and likely higher quality), there are:
● H&N Field Target Trophy Power 14.66gr (0.026BC)
● H&N Baracuda Power 21.14gr (0.044BC)
● H&N Rabbit Magnum Power 25.31gr (0.039BC) [The Rabbit pellet is not known to be liked by many barrels, but it could be worth a try.]
Matthias
PS: I had some errors in this post, sorry, now edited.