While the AR-10/SR25 format rifles look like an AR15, everything is bigger and there is little in the way of a true set standard.
Thankfully, many of the manufacturers share similar design specifications so it is possible to get aftermarket parts. Less follow the Armalite AR10 format than the SR25/AR308 format but they are out there and you need to know which rifle you have. The M&P10 follows the SR25 format, sort of. You still need to pay attention to the details.
The buffer tube is commercial size.
The upper receiver rail follows the DPMS pattern (I think gen 1, which ever is taller).
Most accessories that fit the SR25/AR308 format work with the rifle.
The trigger and hammer pins are the same size as AR15 trigger group pins and not the larger diameter pins.
The magazines are SR25/AR308 format.
There is something about the barrel that is proprietary but I'm drawing a blank if it's the barrel nut or the extension. I'm leaning toward the extension.
The gas block is a standard .750 diameter block.
The muzzle threads are standard 5/8"x24 tpi.