ORIGINAL: stubblejumper
You can look up reloading data online to find the weight of powder charges.For total gun weight,you need to add the weight of the scope and mounts to the publishedgun weight.
published weight is close enough it's not an exact science since KE doens't even convey felt recoil it's just a comparison exercise.
Scope and mounts are rarely more than 2 lbs more.
Just ad hoc the rest
or take your rifle to a UPS shipping store like I did and force them to weigh it.