Boresight a Rifle and Save Your Ammo

How to get a good boresight the old-school way, plus a higher tech method

One of the easiest ways to zero your rifle scope is to boresight the optic first. It won’t be dead on, but boresighting correctly will save a shooter time and ammunition by preventing the need to walk around a target just to get hits in the sight picture.

There are at least two ways to boresight a rifle, one rather awkward and old school yet functional method, and another techier and much more precise method. But the necessary tech isn’t always available, and tech can and will fail.

So, old school and awkward deserves a look, too.

The Author’s Rig

The rifle I used for this project was the Modern Carbon Rifle (MCR) from Christensen Arms in .300 Win Mag. From my previous review of the rifle: 

“Sub-MOA. Damned fine trigger. Carbon fiber throughout and lightweight. And a muzzle brake that actually tamed recoil in a .300 Win Mag bolt action. That’s the short bio of the very impressive MCR. It’s a hunting rifle for Western adventures, a lightweight rifle you can carry all day and can easily make a 400-yard shot on a trophy elk or mule deer.”

The scope was the EOTECH VUDU X 2-12x40mm. A second focal plane rifle scope, the Vudu X features a 40mm objective lens and a rugged 30mm aluminum body. Sharp images with clear edges and bright colors made my shooting that much easier. As for the knobs, the elevation and windage adjustments were a very precise .25 MOA per click.

The illuminated Vudu BD1 reticle in the glass features bullet drop marks below the crosshairs and it’s powered by a single CR2032 battery.

For ammunition, I relied on Terminal Ascent from Federal Premium, a round I’ve used in .300 Win. Mag. and 6.5 Creedmoor with excellent results. 

Old School Boresighting

To boresight the old-school way, head to the range or at least somewhere with a target at a measured distance of 25 yards. Using a target with a measured grid is best. 

Then, set up your rifle on as stable a platform as possible that will still allow you to physically look down the rifle’s bore from the breech. Stability is very important! Use a bench rest or even a gun vise, or create a solid platform with shooting bags — as many as possible.

Next, if it’s a bolt action rifle, remove the bolt. 

Get behind the rifle and line up the scope’s crosshairs on your target. With the rifle kept in place, look down the bore of the barrel through the bolt opening. Now, go back to the scope.

The bore and the crosshairs are most likely aimed at different spots on the target. There might be a few inches difference or it could be a foot off. Now, carefully adjust the scope’s elevation and windage turrets until the crosshairs have been shifted to the bore’s point of aim.

Doing this should at least get your first shot on paper. Send it and find out.

This method will not work with most semi-auto rifles, lever guns, or any shotgun but a bold action. You’ll at least need some kind of laser boresighting device for those (see below), because you simply can’t look down the bore from the breech. 

However, you can make the old school method work for AR-style rifles. Remove the bolt carrier group from the upper receiver along with the follower and the spring from the buffer tube. Reassemble the upper and lower with the rear takedown pin engaged. 

Then, remove the stock from the buffer tube. There should be a small hole in the back of the tube. Since it’s an inline rifle design, that hole will then allow you to look straight through the bore. You might have to remove a screw to access that hole. Once the rifle is on a stable mount, follow the steps above. 

Bore Tech – How To Use a Laser Boresight

A number of boresighting devices are available. I used the Sightmark .300 Win. Mag. Boresight. The unit is essentially a brass case (minus the bullet) with a laser pointer inside. I unscrewed the rear of the unit and inserted a pair of tiny AG5 batteries (included), and the red laser activated.  

I inserted the Boresight into the MCR’s chamber and closed the bolt. My target sat at 25 yards, a white rectangle of paper approximately five-by-four inches. With the Vudu’s reticle centered on the paper, the red laser dot appeared just off the lower right edge of the paper. 

To see just how accurate the Sightmark unit was, I removed the Boresight, replaced the bolt and loaded and fired a round, the scope’s crosshair on the paper’s high center. The round drilled in just off the lower right edge of the paper.

Accurate!

I re-inserted the Boresight, and with the rifle held still, clicked the scope’s turrets to move the center crosshair to line up with the red laser dot. After removing the Boresight from the chamber, I re-inserted the bolt, loaded the MCR and shot.

I hit center paper and a bit high.

So, a whole two shots for get my 25 yard zero, thanks to the Sightmark Boresight, and one of those was just to double-check that the device was working.

Sightmark makes several boresighting models for a wide selection of rifle and handgun cartridges, and even shotgun shells, which means you can get a solid boresight that will have your first rounds hitting paper with practically any firearm.

Fine Tuning

Of course, old school or new, neither boresighting method is the end of the zeroing process. You will still need to adjust your scope for greater precision and at greater distances. I typically zero my rifles at 100 yards.

Once my 25 yard shooting was completed, I moved to my 100 yard lane shooting at green Birchwood Casey Target Spots. The elevation was good on my first shots, but the rounds impacted to the right by a couple inches.

A few quick adjustments on the VUDU X and my last three shots came in at 1.0 inches.

Truly a “group” effort, and one that quickly got me ready for fall hunting!

Editor’s Note: For more great tips from H&B INSIDER Brand EOTECH, check out https://hookandbarrel.com/insider/eotech