Is M4A1 has 16-inch barrel version for military?

[SesameWasher]

I just saw they used 14.5 inches but I never thought they used 16-inch barrel..

 

[saumyasupratik]

No they don't.A CAR-15 can have 14.5", 16", 11.5" barrel and so on.AN M4A1 Carbine specifically has a 14.5" barrel with a step down for the mounting of the M203 grenade launcher.Most 16" barrel CAR-15's have a straight barrel with no step down.

 

[SesameWasher]

another question: is TAR-21 more accruacy than M4A1 (14.5inch)？

 

[saumyasupratik]

another question: is TAR-21 more accruacy than M4A1 (14.5inch)？

Yes.
TAR-21 and STAR-21 have 18" barrel respectively so they are more accurate than the M4A1.The CTAR-21 which is a carbine variant of the TAR-21 has a 15" barrel it is comparable to the M4 in terms of barrel length and both of them have more or less have the same accuracy.

Due to being bullpups in nature the TAVOR has lower sight radius than the M4 so while using iron sights the shorter M4 maybe more accurate.Although the TAR-21 will outperform the M4 when using optical sights like red dot sights and telescopic sights.