The 9×21mm Gyurza (Гюрза, Russian for "blunt-nosed viper") round is a Russian handgun round designed to defeat body armor that was developed by TsNIITochMash for its SR-1 Vektor semi-automatic pistol and SR-2 Veresk submachine gun.

The method of construction of the rounds allows them to be effective against both unarmored and armored targets. The bullet has a hard sub-caliber core contained within an outer sleeve and separated from it by a polyethylene layer. If the bullet strikes an unarmored target, it holds together to produce a wide wound channel. If the bullet strikes an armored target, the sleeve is stripped away, and the core penetrates alone. The 7N29 AP loading fires a 6.7 g (103 gr) bullet at 410 m/s (1,300 ft/s) with 560 J (410 ft⋅lb) of muzzle energy and will reportedly penetrate two 1.2 mm titanium plates, plus 30 layers of Kevlar, at 50 m (160 ft). The disadvantage of the rounds is that high impact velocities are needed for them to work effectively, so the bullets are relatively light to maximize their muzzle velocity. This means they will lose velocity relatively quickly, limiting their effective range.^[2]

SP-10-UCH – unloaded training cartridge^[3]

SP-10 (7N29, sometimes referred to as RG052^[1] or RG054^[4]) – armor-piercing bullet with hardened steel core^[5][6][7]

SP-11 (7N28) – standard FMJ bullet with lead core^[8][9]

SP-12 – low ricocheting, expanding bullet^[10][11]

SP-13 (7BT3) – tracer AP bullet based on 7N29^[12]

SP-17 – bullet with reduced environment penetration^[13]

• 9×21mm Gyurza
• 9mm Gyurza

• SR-1 Vektor
• SR-2 Udav
• SR-2 Veresk
• Gepard (submachine gun)

• 9x19mm 7H21, 9x19mm 7H31 — Armor-piercing variant of 9×19mm Parabellum
• 9×30mm Grom — Uses RG054 Bullet