I have seen three big bore Dakota 76s with stocks split behind the tang, and one of those (a .450) was splintered irreparably.

All with double cross-bolted stocks. The cross-bolting was not tight against the action bearing surfaces and the tangs had not been properly relieved. The barreled actions were simply moving rearward an excessive amount with each shot. All three of these rifles had very nice wood, too.

I have seen other big bore Dakota 76s that did not have these problems. But before buying one, and definitely before shooting one, I would pay particular attention to the stock and its bedding.