I didn't say traditional arts wouldn't be used.  I said they would have left off what no longer worked and moved on to what did.  In the absence of a systematized martial arts tradition (as is the case in most of polynesia) this leads to erosion or total loss of the art.  On a local level, it differed on a case by case basis, but if you think Maori warfare didn't change post-contact, I think you'd be in the minority.

Speaking of rifles,

Here is a nicely carved Maori rifle in the Auckland Museum