Even when properly installed, the position of a carbine’s free-floating handguard shifts slightly during use relative to its barrel, which can cause serious accuracy issues if the firearm’s front sight is affixed to said handguard—as is typically the case. Ultradyne’s Mercury/C4 Dynamount Sight Combo remedies this problem by pairing the company’s Mercury muzzle device with its C4 Precision Front Sight, which mounts to (and times with) the Mercury itself instead of to the rifle’s handguard. Threaded 1/2x28 TPI for use with .223 Rem./5.56x45 mm NATO firearms, the Mercury features three progressive side ports for a longer, less sharp recoil impulse. Using an innovative aperture post, the folding C4 Precision Front Sight offers an intuitive circle-in-circle sight picture when used with an aperture rear sight. Available with ($349) or without ($199) the C4 Precision Rear Sight. Contact: Ultradyne; (573) 299-0900; ultradyneusa.com.