With any kind of oriented strand board made for construction, the grain of the layers is laid out for uniformity for even load distribution and sheer stresses. On a regular wood rifle stock, the grain should be parallel to the barrel, because wood is far stronger by about 2x going with the grain than perpendicular to it.
So, unless you're doing layers of strong resin like on most laminate stocks (which adds weight as well as strength), I'd say it's probably not worth the aggravation of trying to shape and finish sand a stock with all sorts of end grain coming out at various angles all over it. You can really hurt your tools working on that dried resin too. At the end of the day with half the strands oriented in the wrong direction, it won't be as strong as laminated stock whose blank was purpose-built.
But hey, if it's a project for fun, try it out! After you get it sorted you can move on to some nicely figured walnut. Take a look at a 91/30 Mosin's laminated stock for inspiration. But be warned, a lot of the plywood out there looks great on the outter layer on both sides, but the inner layers can be hole-y and ugly.