When making major changes to a weapon such as giving it a projectile, you want to make a copy not a child THEN re-parent it to the rocket launcher.
Also, make sure “Anim BluePrint Generated Class” under Mesh3P is set to none and the one under Mesh1P is set to the rifle.
Just to verify it’s correct, right now I copied the rifle, named it WeapRocketRifle re-parented it to the rocket launcher and the only thing different was “Anim BluePrint Generated Class” so I set it to none like the original rifle and voila:
[video]https://youtu.be/K1ECWfSzqqI[/video]
I then right clicked my new rocket rifle and selected “Create Blueprint Based on This”, named it WeapRocketPistol, changed the animations, changed the clip count, changed the TPV and FPV mesh and got this:
[video]https://youtu.be/1cXtovLVC9k[/video]
Finally i set the pistol to use the plant projectile:
[video]https://youtu.be/YyG6Bd9TqJQ[/video]
All said and done it took maybe 15 minutes. i’d suggest starting over with a fresh copy of the rifle. Once you have that working properly with your new projectile make a child of it for each other weapon you want to do. You can also do copies instead of children for each weapon if you want.