After reviewing the chart, according to it the S&W comes up short on these features.
S&W
No M-16 FA bolt carrier
No HP testing barrel
No MP testing barrel
not milspec barrel steel
not 1:7 rifling
no double handguard shields
no heavy buffer
After reviewing the chart and correcting what BM has or offers on some M4 models these are the only features minus.
Bushmaster M4
No black extractor spring insert
no 1:7 rifling
no finish under FSB
no milspec reciever extension
no staked reciever end plate
no heavy buffer
But what does this mean for anyone who buys either, absolutely nothing. If you want an H-buffer, they cost about $12 or so.
Its not hard to stake anything if you do it right, and its free.
The commercial extension tube is thicker, made of the same materials, and stronger, the stocks are all available for it as well milspec tubes.
After many many years the lack of finish under a FSB leaves no damage, and causes no ill effects.
1:7 rifling twist is only needed for stabilizing heavier bullets, but is not needed for 55gr or 62 gr bullets, even heavier. 1:7 rifling may cause more rapid wear to the barrel compared to 1:9.
M-16 FA bolt carrier, you dont need it for use on a semiauto AR, but if you wish to buy one they cost the same as the SA AR15 carrier does.
HP testing barrel
MP testing barrel
milspec barrel steel
These features are not specifically better, or more durable for a semiauto AR rifle.
Remember milspec only means the minimum standard for a military contract, right now the companies with military contracts for these rifles are not even included in the chart, colts contract ran out.
Heres a Bushmaster FA bolt carrier for an M4 rifle (the left carrier), so it is standard on one model of M4.
The carrier on the right is a standard DPMS AR semiauto bolt carrier.