If you have a 14.5" barrel and perm-attach an extended A2 FH (like BCM's) what is the actual OAL length difference from a regular FH? I have a 6921 upper I'm going to do this with and when I laid the BCM FH alongside the upper as is it only looked maybe 0.2" or 0.3" difference?

A 16" barrel with a regular A2 FH has got to be ~ 17" long or so.

Maybe a better way to put it is this: a 14.5" barrel with perm-attached FH (to bring it to 16" OAL) is how much shorter than a 16" barrel with a regular A2 FH?

I just measured a BCM 14.5 inch barrel with permed A2X (rod down bore, touching bolt face) and it was just under 16.5.  Different rifle with a 16" barrel and standard A2 hider was 17.5".

So basically you knock off an inch.

Thanks for checking.