Bore sighting my Model 1885, 270 WSM by looking directly down the center of the barrel and setting the rifle scope's crosshairs to match.
Here are some simple ways to bore sight your hunting rifle scope, no gadgets or lasers required.
There are two ways that I bore sight my rifles that I have found will get me within six or so inches of being sighted-in at a hundred yards.
Look Through the Barrel Bore Sighting
The first method works on any rifle that you can remove the bolt or open the action and be able to see through the barrel from the back of the rifle. Bolt action and single shot rifles will work for this method. With your target set out at 100 yards place the rifle in a shooting sand bag or something that will hold the rifle very still. Open the action on a single shot or remove the bolt on a bolt action rifle. Position the rifle so when you are a step or two behind the rifle and look straight down the middle of the barrel you can see the middle of your target at 100 yards. Once you have the barrel pointing straight at the target carefully step up to the rifle and look through the scope without moving the rifle. Now adjust the scopes reticle to lineup with the center of your target.
You may want to go back and forth from looking through the barrel to looking through the scope a few times to make sure you are on. That's it! No lasers or fancy gadget required. I have always been within six inches of being sighted-in with this method. You may also wish to take your first shots at 25 yards, adjust as needed then move out to 100 yards. I have been just fine at going straight to 100 yards and have the bullets place on paper.
Mirror Bore Sighting
My second method works for any rifle regardless of the action type. This method works great for your windage adjustment but not so great for your elevation adjustment. However, I have found most of my initial scope adjustments to get a rifle sighted-in are windage adjustments not elevation adjustments.
In this method you will need to find yourself a mirror that you can get far enough away from to where you can see your reflection clearly while looking through the scope. Now position yourself in front of the mirror and look through your rifle scope directly at the reflection of the rifle. Point the rifle so that the barrel is pointing perfectly straight at it's self in the mirror. Once you have the barrel pointing straight adjust the scope's windage adjustment to line directly up with the barrel. Your rifle scope is now bore sighted for windage.
I could go into a lengthy ramble of how you can adjust for elevation but for most it is best to leave it alone until you get to the range or use the "look through the barrel method" if you can with your rifle. Just know that you might need to adjust the vertical shot placement a little more once you get to the range.
I started using the mirror method looking for a way to adjust for the large amount of windage adjustments I have to make on my Model 1885s. At least with my Model 1885 rifles the drilled and tapped front is not aligned perfectly with the rear. Using the mirror method is a great way to quickly adjust the windage with the windage adjustable rear base before I lock the base in place. Then I can use the "look through the barrel method" to get a more precise bore sighting. I used the mirror method on my X-Bolt and it worked great as you can see in the Accuracy of my New X-Bolt Stainless Stalker, 270 WSM entry.
If you need some targets to sight-in your rifle you can get DIY Hunting Rifle Target Downloads.