It has been suggested they are bushmasters. FSBs are not F marked.
The top one is T marked. On the FSB, there appears to be a BOM to the left of of gas tube pin, possibly a 1V before it.
The bottom one is not T marked.
Both have different barrel profiles. They came from a military unit about 2 years ago.
my money is on bushmaster for the bottom… looks exactly like a couple i’ve had come through my shop here. i don’t recall any markings, but i don’t recall looking for any- so that helps not.
bushmaster is real big on the bull under the handguards on their shorty barrels… not sure why…
Bottom looks to be bushmaster.
Not sure on the top.