When evaluating gun knives, the blade material is the most critical factor; look for high-carbon stainless steel (e.g., 8Cr13MoV, D2, or S30V) for superior edge retention and corrosion resistance. The locking mechanism (such as liner locks or frame locks) must be tested for zero blade play to ensure user safety. For bayonet-style knives, verify the mounting bracket dimensions and barrel ring diameter to ensure compatibility with specific firearm models. Additionally, the handle should feature G10 or aircraft-grade aluminum with an anti-slip texture for a secure grip in tactical environments.