More information is required. Make / model of nail gun Size of cable to garage Length of cable run to garage How sockets are wired Size of cable to sockets
An MCB is designed to protect the cable, not what you connect to it. So if you were to "insert a bigger breaker" it may be that the cables are not big enough to cope and you end up causing a fire. This nail gun, is it brand new?
I would guess problem is inrush, you may get away with a C16 instead of B16 MCB, but the real point is the nail gun is poor design.
The letters on the MCB are what the magnetic part of the MCB will trip at, B = between 3 and 5 times thermal trip rating, C = 5 to 10 and D 10 to 20.
So for the B16 to trip it is drawing over 48 amp at start up, that is a lot of power.
The magnetic part of the MCB will work in about 0.01 seconds, where the thermal bit can take 1/2 hour depending on how much over load, but to ensure with a short circuit the magnetic part will work we need to measure the loop impedance so a B16 needs 2.73 ohm to trip, and a C16 needs 1.37 ohm, so before it is changed you have to measure the loop impedance, the problem is the tool to measure it with costs over £150 so not really a DIY job.
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