Define "tougher more durable wood" VBG
. Our gunstock maple has more of a twisted, braided grain which makes it mechanically stronger that straight grain walnut since
most native american walnut has a more open grain structure. Hybrid and grafted walnut
may be a bit better.
I think that given similar grain structures walnut may be slightly more brittle. When it comes to the fancy and complex grains, anything can happen.
One problem in comparing is that there are several kinds of maple (also true for walnut as well) and even within those kinds relative strength can vary incredibly depending on the actual growing conditions and the grain structure of a specific tree and how it has been treated since the tree was cut down and sawn into stock slabs. Another factor is that most of us want some nice looking wood and few of us look at our guns as impact weapons.
The lumber/timber industry has several scientific scales that can serve to compare various woods for differing usages. those scale might prove enlightening. One can also consider the various woods the military allowed to be used for gunstocks, production costs and availability were considerations but up to and through the end of WW2, and even Korea the military specified stocks that would serve if needed as impact weapons and also to handle the leverage issues of bayonet use. To the best of my recollection, mil spec called for Walnut, beech, and elm.
Just as an aside, I wish I had had the foresight to secure some of the old er--er--er "water" or swamp elm we cut for firewood on my grand dads farm as a kid. They had been killed by the Dutch elm disease and were pretty seasoned while still standing. The fibres were so twisted and braided that it could only be split in the dead of winter when the moisture in it was frozen. Some of the larger logs were quartered with small 1 or 2 inch charges of dynamite placed in holes granddad augered along the length of the trunk. I suspect it'd have made a heck of a stock once shaped stained and finished, but it'd have been a nasty beast to carve
