Glock G31 Gen4 357 Sig 4.49in Black Nitrite - 15+1 Rounds - The Glock 31 Is About The Size Of A Medium-frame .357 Service Revolver But Much Lighter, With 10/15/17 Shots Instead Of 6. The G31 In .357 Delivers The Same Legendary Stopping Power As The Old Magnum round. The GLOCK 31 Gen4, in 357 SIG, is the optimal solution for those seeking high muzzle velocity and superior precision in a reliable, yet lightweight, pistol with large magazine capacity. The Modular back strap system makes it possible to instantly customize its grip to accommodate any hand size. The reversible magazine catch makes it ideal for left and right-handed shooters.