The 40x46mm low-velocity SL40 grenade launcher has been in Australian Defence Force service for some time now, serving primarily as a modular under-barrel grenade launcher attached to the 5.56x45mm NATO F90 service rifle within the infantry at the squad or section level. It was first chosen to accompany the F90 family of rifles in 2014, a derivative of the Austrian Steyr GL40 launcher (the SL40 being a derivative of the GL40). The original design competition was between the Steyr GL40 and the Madritsch Weapon Technology ML40AUS, another Austrian armaments company. The Steyr design was selected for integration.
Currently, Steyr does offer a UBGL/Standalone grenade launcher, however it is somewhat different in the construction of the pistol grip/trigger guard than the Lithgow Arms SL40. Known as the GL40, it has actually evolved to being adapted to the RS556 rifle as the RS40.
While touring Lithgow Arms, we were able to get an in-depth look at the launcher, in addition to observing staff shoot practice rounds through it at the historic rifle testing range adjacent to the grounds of the factory itself. Unfortunately, we couldn’t any HEDP on hand, the “Orange Death” would have to do for the photo and video shoot. Readers should be able to see some footage of the SL40 in action in several upcoming TFB TV episodes on Youtube.
The SL40 is a single barrel, breechloading grenade launcher with a tilting barrel that is pushed to the left to extract or insert rounds. This allows it to also accept non-standard 40mm grenades such as white star clusters or crowd control munitions that otherwise wouldn’t fit in the confines of an M203. The barrel pivots on a hinge located on the right side of the muzzle. Unlatching the barrel involves pressing a latch on the left side, just above the safety selector (pointing up is Fire, pointing towards the shooter is Safe). Although this safety selector is ambidextrous, the pivoting of the barrel and the latching mechanism is not, thus confining the use of the SL40 to the support hand of a right-handed user or the firing hand of a left-handed user. Due to the barrel being 7 inches in length, we asked Lithgow Arms staff if it had any detrimental effect on accuracy or velocity compared to longer, conventional launchers and the answer was that it didn’t. The launcher weighs in at 1.025kg or almost two and a half pounds.
Firing the SL40 involves pulling the “trigger” to the rear. This trigger is actually a circular piece of metal that protrudes through an opening in the trigger guard of the F88 rifle and rests just below the actual trigger of the rifle. This gap uses a shaped piece of plastic to fill itself when the grenade launcher is not attached. Losing the plastic chunk would not affect the operation of the F90, thus it has been “soldier-proofed”.
Aiming the SL40 is done by adjusting a 7 MOA Trijicon RMR red dot sight to the correct range on a sliding scale and then placing the red dot on target for a point of aim, hopefully, point of impact round detonation. The sight is mounted either just in front or just behind the rifle’s optic, to the 12 o’clock Picatinny rail, using a small latch on the right-hand side. When using the launcher in a standalone mode, the sight can be easily transitioned to the 12 o’clock Picatinny rail. Two versions of the sight are available. The original sight actually had the RMR mounted in a standard position, but newer versions have it changed to a vertical axis so the RMR is actually sideways in the sight. This change was requested by ADF personnel.
The standalone chassis is currently being produced at the Lithgow Arms factory. It is a very simple, lightweight piece that simply allows the SL40 to be slid underneath it and mounted the same way it is mounted on the F90. It is equipped with an M4 buffer tube that has a Daniel Defense DDM4 telescoping stock mounted to it. There are two QD points on the standalone chassis, one on the forwardmost portion, just underneath the Picatinny rail, another on the DDM4 stock. The pistol grip is an Ergo AR15 grip.