The rifle (Spear is its commercial designation; M5 is the military one) is an evolution of the SIG MCX, which is in turn an evolution of the AR-15 and AR-18 systems. The MCX move the recoil spring assembly into the top of the upper receiver, allowing the use of a folding stock. It also has very easily swapped barrels and a suite of fully ambidextrous controls. Scaled up to AR-10 size and chambered for 6.8x51mm, the MCX became the Spear.
That new cartridge (commercial designated .277 SIG Fury) is designed to produce high muzzle velocities out of short barrel (the M5 has a 13 inch barrel).It does this by boosting the operating pressure up to an eye-watering 80,000psi, which required the development of hybrid case using a stainless steel case head. This allows the case to handle those pressures safely. The currently available commercial ammunition is loaded to lower pressure, however. Much of the military and civilian use of this rifle will be done with downloaded training ammunition, which uses a conventional all-brass case.
Both the M5 and M250 were ordered by the Army with suppressors on every weapon, a significant advancement in Army policy. The can is another SIG development, entirely made using additive manufacturing and designed specifically to prevent gas blowback into shooters' faces (which is succeeds at wonderfully).
Overall, I believe the M5 / Spear is an excellent rifle - soft shooting, reliable, and very accurate. However, that does not mean it is the right rifle for the Army. Will its ability to defeat modern body armor prove worth the tradeoff in extra soldier combat load weight and reduced ammunition capacity? Only time will tell...
VIDEO HERE (35:12 minutes)
*****
I'm sorry, but I don't share Ian's enthusiasm.
With a hybrid case, I can see case separation happening, and the fact that there's two different types of ammo, a combat round and a training round? Sorry, they need to eliminate the training round and be shooting the shit out of those combat rounds instead if for no other reason than to make sure the bugs are all worked out.
Then there's the suppressors..... they say it's to reduce noise on the battlefield. Will somebody explain to me how the suppressor will muffle the sound of mortars, grenades, artillery and bombs that are common on battlefields? They're a hell of a lot louder than rifle fire.
I could go on and on about it, but I'll spare you.
