The Sightmark boresight is an in-chamber laser boresight designed for firearms chambered in .223 Remington and 5.56×45 NATO. Its brass housing and 632–650 nm visible red laser help provide an initial alignment for a riflescope, red-dot sight or iron sights before final range verification.

Suitable for use

• Preliminary sight alignment on .223 Remington firearms

• Preliminary sight alignment on 5.56×45 NATO firearms

• Checking a newly installed riflescope

• Initial adjustment of red-dot and reflex sights

• Checking iron-sight alignment

• Verifying sight settings before visiting the range

• Hunters and target shooters

• Keeping as a compact calibre-specific tool in a range bag

Why choose the Sightmark SM39001?

• Compatible with .223 Remington and 5.56×45 NATO chambers

• Installs directly into the firearm’s chamber

• Visible 632–650 nm red laser

• Manufacturer-specified sighting range of 15–100 yards

• Approximately 2-inch laser dot at 100 yards

• Durable brass construction

• Simple on/off end-cap operation

• Approximately one hour of battery life

• Batteries and protective carrying pouch included

• Compact and easy to transport

• Helps reduce the time and ammunition required for initial sight adjustment

Technical specifications

• Compatible calibres: .223 Remington and 5.56×45 NATO

• Laser type: Visible red laser

• Laser wavelength: 632–650 nm

• Laser output: Less than 5 mW

• Sighting range: 15–100 yd / approximately 14–91 m

• Dot size: 2 in at 100 yd / approximately 51 mm at 91 m

• Power supply: 2 × AG5 or 3 × AG3 batteries

• Battery life: Approximately 1 hour

• Operation: On/off end cap

• Body material: Brass

• Operating temperature: –10 to +50 °C

• Intended use: Preliminary sight alignment

• Ammunition status: Not ammunition or a snap cap

Supplied with

• Sightmark SM39001 laser boresight

• 3 × AG3 batteries

• Protective nylon carrying pouch

• User manual

Frequently asked questions

Is the Sightmark SM39001 compatible with both .223 Remington and 5.56×45 NATO?

Yes. The manufacturer specifies compatibility with firearms chambered for either calibre. This refers only to the fit of the boresight and does not mean that .223 Remington and 5.56 NATO ammunition is interchangeable in every firearm.

Can this laser boresight provide a final zero?

No. It indicates the approximate direction of the bore and is intended for preliminary sight alignment. The final zero must always be confirmed with suitable ammunition at an authorised shooting range.

How is the Sightmark boresight switched on and off?

The laser is activated when the batteries are installed correctly and the end cap is secured. After use, remove the boresight from the chamber and take out the batteries.

Is the red laser visible in bright daylight?

Visibility depends on ambient light, background colour and distance. The red dot is easiest to see indoors, in shade or in reduced light, while its practical range may be shorter in direct sunlight.

When is the Sightmark SM39001 the right choice?

This model is well suited to shooters who primarily use a firearm chambered in .223 Remington or 5.56×45 NATO and want a compact tool for preliminary sight alignment. Its calibre-specific brass body fits directly into the chamber and does not require adaptors to be inserted into the muzzle.

A universal boresight may be more practical when several unrelated calibres need to be checked. The comparable Firefield model offers similar basic specifications. No laser boresight replaces final range verification because the actual point of impact is affected by the ammunition, distance and characteristics of the individual firearm.

Expert recommendation

The Sightmark SM39001 is particularly useful after installing or replacing a riflescope or red-dot sight. It helps bring the initial sight setting closer to the bore axis before visiting the range. The manufacturer’s instructions recommend using a clearly visible target at approximately 18–27 metres while the firearm is held securely and pointed in a safe direction.

Always confirm that the firearm is unloaded and remove all live ammunition from the work area before inserting the device. Place the boresight into the chamber carefully, without forcing it or closing the action aggressively. Keep the laser away from eyes, people, animals and reflective surfaces. Remove the boresight before loading the firearm. For storage, take out the batteries, leave them inside their protective sleeve and avoid overtightening the battery cap.

Faster preliminary alignment before range verification

The Sightmark SM39001 provides a simple way to pre-align the sights of a .223 Remington or 5.56×45 NATO firearm. Its brass body, straightforward operation and protective carrying pouch make it a practical addition to a shooter’s maintenance and range kit.