Maximum current capacity of this wire?
If copper wire, that's about an AWG 18 wire. 100A is above the fusing current of an AWG 18 copper wire, so without some kind of cooling the copper will actually melt with 100A continuous. 

300ms (with sufficient time between pulses for the wire to cool) might be "okay" due to the heat capacity of the wire (you'd have calculate it out) but the wire will get very hot and probably smoke a bit, and perhaps could set things on fire. Any insulation other than something like a quartz tube might be degraded or destroyed, and the wire will tend to oxidize and droop under gravity.  

If the wire is other than copper then then answers will be somewhat different, but the approach would be the same.