Spectre meltdown.
 

So put my upgraded gearbox back into my M4 and eveything was all fine. Went to the field today, plugged in the battery. Took a test shot.... Then all of a sudden it just fire full auto by itself. Then noticed the lypo starting to smoke and melt. Thought the odd smell came from the battery but it was acually the spectre. Tryed a new lypo and and same full auto effect. Thinking a wire may be grounding out . Did I ruin the unit or may I be ok ?

Unless a trigger wire is being grounded out somehow and for some reason it's not firing semi, it's ruined.
When you break a mosfet is either fuses open or closed. Yours fused closed.

Thats a upsetting prognosis doc. Im hoping it a grounded wire then. Going to put her under this morning and I let you guys know if she makes it. BTW if it was not a grounded wire ... What would cause this to happen ?

If it wasn't a grounded wire, then a large amp spike is usually what causes mosfets to fail

you might be lucky and you just had a short on the trigger wire, look for a pinched wire. A lot of the hardware on the spectre is very robust. if the trigger wire was somehow shorted you might be ok if you find where it pinched.

If the motor power feed shorted to the trigger circuit it took max amps on the trigger circuit rather than the motor circuit, the fet chip is likely dead as you smashed a log into a hole meant for a toothpick.

There is no trigger wire. The third wire is a braking wire.

Take the FET out of your gearbox separate the halves and inspect wiring. Plug a motor in, plug a battery in with the motor clamped or held firmly. If the motor spins as soon as your battery is plugged in, then RIP.

sounds like what happened to my buddy.
Believe his was toasted and has to get a new one.

Thank you Baby Airsoft Jesus. It was a pinched/cut wire in the buffer tube. Covered it up and working just fine. Thanks for the info fellas ☺