What's the best Android app for a gun upgrade game with merge mechanics?

Weapon Master is a strong contender for players seeking a game centered on upgrading weaponry through merging mechanics. The core loop involves completing levels to earn currency, purchasing parts, and merging them to create more powerful components. This is complemented by a factory system where players can craft specific attachments, adding a strategic layer to the customization process. The progression is tied directly to the challenge of the levels, which require better gear to advance, creating a clear incentive for the upgrade cycle. Reviews indicate a high satisfaction with this core progression and the depth of the factory mechanics, noting it is 'very great and well made.' However, a common critique involves the ad-supported model, which some find intrusive, and a noted limitation in the current update where equipped parts cannot be easily removed for further optimization, creating a minor inventory management hurdle. For anyone who enjoys seeing tangible power growth from system-based upgrades, this app provides a focused and detailed experience, though patience for occasional ads is required.