This run the dual melee weapon by each feature.

INFORMATION
this is old, if want to simply use, I recommend install the Dual melee weapons of new version.

//Introduction
This is using each esps feature and become melee weapon.
however it might are tricky.
Ck are very slow and pex compile also don't have enough resource on my environment so that,I needed use each esps feature for realization.

//require
Fallout Samurai Set(for use quickly because custom animation need ck's metadata)
MCM, F4SE(for run the HK USP.45 Tactical)
HK USP .45 Tactical(this pex are including feature for realize the dual)
Dual Wield Master (it's not require but I strongly recommend for dual animation)

//Install
1:Setting animation source.
install the Fallout Samurai Set and overwrite from those hkx to  hkx of Dual Wield Master.
after this, specify the esp of Fallout Samurai set to master by ck or editors.
if don't have this, use the option. I think this is specified already.

2:Setting dual weapon.
install HK USP .45 Tactical and overwrite the esp of this page and put the meshes as loose file.

3.Using weapon
get and equip the HK USP45 that became already melee.

//Uninstall
remove the loose files of this page and overwrite from those to origins.
if continue to use HK USP.45 and Fallout Samurai Set as original, absolutely return to the origin esp file and remove the loose files.

//Change Weapon graphic
[Right Hand]
choose graphic by weapon workshop.
"Extra rail mod" and "suppressor" will be effect to graphic if put the uploaded loose file.
however maybe some graphic are incorrect because the source esp are pistol module.
[Left hand]
choose graphic by mcm menu like knife of source.

//Other
if would like to change to the another meshes, it able to change by Outfit Studio and nifscope and overwrite meshes to loosefiles except "rail", "USP45Barrel", "USP45Magazine" and "USP45Reciever". 
the right hand are not set weight and left hand are set so sometimes right hand require nord data so if so, use the nisfcope.
about Outfit sutdio and nifscope manual, please read them tool.

//merit
we can use melee like dual melee weapon.
The dual wield animation will run as only this weapon user.

//demerit
HK USP 45 are not run as pistol and lose the this some feature.
Fallout Samurai Set animation will be changed however able to use as melee weapon.

Credit:
Thank you for upload the origin.
Gogy28
toounx