On the top of the barrel near the flash suppressor it should be stamped with the caliber and rate of rifling. Example - 5.56 Nato 1/7.
Yes
1/2 28
Colt has not offered a AR15 in 308
If it is one of the recent Colt .22LR AR15 rifles, then the answer is no - they are completely different internally.
I believe 'pt' stands for patent, as in Colt patent firearms
It should have the caliber marked on the barrel,such as"38 Colt New Police".
You will have to call Colt and tell them the serial number.
Yes it does, unless your barrel is stamped .223 .
Call Colt and they will tell you.
Proofhouse.com. Call Colt also.
@ 40 inches.
The AR15 series