We still have some ash pole corral at the family farm, and I cut some for repairs and for gatesticks in barbed wire gates every few years. When green, it is very supple. A green gatestick will bow into a C shape in a short time under tension. An ash gatestick allowed to season for two or three years is strong, won't bow, and lasts forever.
In corral poles, they are best installed green. They season over the decades to as hard as iron! A 50 year old ash pole needs to be drilled for the spike to hold it to a post if you need to reinstall it. They get a little brittle then, occasionally break at the thin end. .
I know you asked about gunstocks, but from this experience I would say that a good piece of ash, dried properly, would make a fine stock. I would not make the wrist too thin, though.
