B&B Robotics' Bigger Boomer Shtick

This Magical Attachment to the B&B Robotics' Big Boom Shtick augments its firepower, ensures more destruction to come out of you firing it away but makes the rocket launcher even more unstable (as if its possible).

Attaching or removing the Bigger Boomer Shtick from the Big Boom Shtick requires a utilise action, as part of which you must succeed on a DC 20 Intelligence Check, to which you can add your proficiency bonus, if you are proficient with Tinker's Tools. On failure, the Big Boom Shtick Misfires. Once attached, the Bigger Boomer Shtick is considered part of the Big Boom Shtick and provides the following benefits:

Unavoidable: The save DC for the explosion is now 10+Modifier of one of yours Ability Scores of your choosing when attaching the Bigger Boomer Shtick + your proficiency Bonus; or 22, whichever is higher

Additional Charges: While Bigger Boomer Shtick is attached to the Big Boom Shtick, your Big Boom Shtick deals an extra 3d6 fire and force damage 

Double or Nothing: Whenever you roll a 3 or lower on the recharge roll, you may reroll a d6 roll. If you still roll a 3 or lower, you gain vulnerability to all damage dealt to you as a result of Big Boom Shtick firing away and Big Boom Shtick ignores resistances or immunities to damage types you take as a result of it firing away until the end of your current turn. If you successfully recharge a Big Boom Shtick after using the Double or Nothing feature, you can immediately fire it, without using a usually required bonus action to do so.  Once you have successfully recharged a Big Boom Shtick as a result of using the Double or Nothing feature, you can't do so again until you finish a short or long rest.

If the Big Boom Shtick gets destroyed while the Bigger Boomer Shtick is attached to it, it is also destroyed. Bigger Boomer Shtick, however, can be repaired by B&B Robotics, who have a legal monopoly on performing such reparations. Repairing a Bigger Boomer Shtick requires its owner paying a 50000 gold fee and takes 7 days.