So before i watched this video i was shown a very simple technique to get your actors gun in the correct location. So long as your animations put your arms in the proper location, all you have to do is go to your characters bp. Then open up the construction script, pull from the default construction node and add “AttachToComponent”. Make the target your weapon component, and the parent your mesh. Simply add in the name of the socket that you are using to attach the weapon grip to and set location rule to Snap to Target, Rotation Rule to Keep Relative and Scale Rule to Keep Relative. Make sure Weld Simulated Bodies is checked and you are done.
I have had no issues when using the stock UE4 anims, this seems to work with any of the type of guns i have used as well. Anyways, here you guys go. Enjoy!