Fragile Weapons (5e Variant Rule)
From D&D Wiki
Under this rule, every weapon has a number of hit points which cannot be restored even through excellent craftsmanship or repairing spells. Every time a weapon is used to hit a creature or object object, that weapon loses 1 of its hit points permanently. If the weapon has the ammunition property, every attack with it—regardless of hit or miss—reduces its hit points by 1.
As a general guideline:
- Improvised weapons have 5 hit points, simple weapons have 10 hit points, and martial weapons have 20 hit points.
- If a weapon has the ammunition property, it has an extra 5 hit points.
- An uncommon magic weapon has an extra 10 hit points.
- A rare magic weapon has an extra 20 hit points.
- Magic weapons of very rare and legendary have an extra 20 hit points as well, but unlike all other weapons, these hit points can be regained. Such a weapon fully regains its hit points daily at dawn, but only if it has been reduced to 0 hit points since the last dawn. While this weapon has 0 hit points, it appears as nothing but a small, dimly-glowing blue shard that vaguely resembles its former shape.
The DM is encouraged to vary from these hit point guidelines when he or she feels it is appropriate.
When a weapon loses its last hit point, it shatters apart violently, breaking apart into shards of a mysterious blue substance that whisps away into nothingness. If a melee or thrown weapon hits when it shatters in this way, the attack is treated as a critical hit regardless of the attack roll, and the weapon's damage overcomes damage resistance as if it was a magic weapon.
To compensate for magic weapons breaking, the DM is encouraged to treat such magic items as "minor" instead of "major." Essentially, whenever the party would earn a magic weapon of uncommon or rare rarity, they should instead earn three magic weapons or other "minor" magic items rather than only one.
Tracking the hit points for numerous weapons can be more time-consuming, but not much more so that tracking ammunition. For a combat-focused adventure with many attacks, it may be useful to use d20s or d100s to track hit points rather than a writing tool.