what is that game where you buy guns and shoot builds made out of blocks in roblox

The Roblox game you’re probably thinking of is Build ur Base or something very similar, where you buy weapons and shoot blocky builds/base structures. A few other Roblox games with that same vibe are:

• Hypershot — fast combat with guns and abilities.
• Locked 2 — weapon-focused Roblox combat.
• Build ur Base — base-building plus fighting enemies in a blocky style.

If you mean the one where players literally build a block structure and then destroy it with guns , the closest match from current Roblox results is Build ur Base.