Archimedian Repeating Crossbow

Made of a Metal Stock with a Gas Canister builtin, Wodden bow with Brass Fittings, a Silver Bow String, and Equipped with a 20 Round Drum Magazine, This Crossbow is a unique Weapon with a selective Fire mode.
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1: Single Shot: 2d12 Piercing Damage... The Semi-auto fire mode allows for accurate fire on a single target. shots made with this mode are made at Advantage

2. 3 Round Burst: 3d8 Piercing Damage in a 15 foot cone ....Roll 1d20 to Determine Misfire. On a Die Roll of 5 or higher, all creatures in a 15 foot arc must make a DC 16 Dex save, taking full damage on a faild save, and half as much on a
Successful one

3. Full Auto: 4d6 Piercing Damage in a 30 foot cone... Roll 1d20 to Determine Misfire. on a Die Roll of a 9 or Higher, all  Creatures in a 30 foot arc must Make a DC 14  Dex Save, Taking full Damage on a faild save, or None on a Successful one. Additionally, until the end of their next turn, all targets that fail the save have DISADVANTAGE on all attack rolls.
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Additionally, This Weapon uses a self refilling Gas Canaster. The gas canister, at dawn of a day, has enough power to make 100 shots(Each Bolt thatt is fired using on of these abilities counts as a Shot).This Bow must be loaded with custome ammunition that can be commisioned at a Fletcher.

Lastly, Depending on the Mode of fire that is selected, the Weapon has an Increasing Likelyhood to Misfire and Jam. 
When a Misfire happens, the Character must spend the rest of their turn UnJamming the weapon.
Single Fire: Misfires on a 1 or a 2.
3 Round Burst: Misfires on a 1- 4
Full Auto: Misfires on a 1-8
NOTE: The Mis fire is based on the DICE Number, NOT THE TOTAL.

Proficiency with a Heavy Crossbow allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, Damage, Combat, Ammunition, Heavy, Loading, Range, Two-Handed, Push