I also agree with the pull the bolt, line up the bore with target at 100 yards, and line up scope. Don't waste your money with a boresighter, But don't take our word for it, think about it.
And this is why.
Let's say you have a brand new chamber in a brand new barrel. Let's also say the laser tool you insert into your chamber has 2 THOUSANDTHS of play, per 1" of that tool so you can insert and extract it somewhat easily.
Now, it's just simple math. 300 feet in a hundred yards X 12 inches per foot. 3600 inches.
.002" of play per inch of tool X 3600 = 7.2" at 100 yards.
your laser will be off that much. I can usually get it closer than that with my eyeball. I dont know exactly how much slop those units have, But, I feel like I am possibly giving them too little tolerance. I have personally seen some that were off by 4'. It just depends on how it fits your chamber. Hope this helps.