I know that generally, a 14.5" upper and an A2 FS (perm attached) do not yield a 16" upper.  However, I also hear that the way a barrel is measured on an AR is by closing the bolt and dropping a dowel down the barrel and marking the length.  If that's the case, I have a 14.5" upper w/A2 perm FS that is indeed 16".  I have seen some custom 15" barrels out there, so to make sure I compared this barrel (a DPMS M4 barrel) with a CMMG 14.5" M4 barrel (w/perm Phantom FS) and the barrels are indeed the exact same lenght up to the flash suppressors (one has the Phantom and the other has the A2).  The only thing that occurred to me that may make it 16" (since it's EXACTLY 16" according to the dowell I dropped in it) is that the washer on the barrel before the FS seems to be a fairly thick crush washer.

Any comments on this?  

Someone else recently mentioned they got a 14.5" +A2 to 16" by using some kind of thick washer.  So it certainly seems possible.

My only question would be that gap between the muzzle and the begining of the FS - how does that effect accuracy and flash supression?  

So that is the correct way of measuring a barrel length?

Quoted: So that is the correct way of measuring a barrel length?

Yes, bolt closed, drop in a dowel and mark it at the muzzle.  Measure from the end of the dowel to the mark.

Have done two barrels like that:




More pics here:

ar15.com/forums/topic.html?b=3&f=118&t=231110

There is a large gap between the crown and the flash hider.  Ran one like that for over 10 years, and that combo was quite accurate (for what it was).  Suppose at some point you could get a bunch of carbon in there and have a problem?

Seems to me the biggest draw back is that the flash suppressor is only threaded about 1/2 way onto the barrel.

It still needs to be permanently attached, so what do you gain, other than a look and maybe some extra attention from some knowledgable LEO type.  I would be able to immediately see that you don't have a 16" M4 barrel and yet you have an A2 FH .................................... hmmmmmm .................... as a LEO (hypothetical, of course), I might need to look into this.  Likely to happen, no, but it can and the grief from it isn't worth "the look", IMO.

I have also found out that many barrels aren't exactly the length that is advertised.  As a matter of fact, my 16" Colt M4 barrel measures a tad over 16" to closed bolt.  Others have measured very similiar, a tad over the advertised length.

Quoted: As a matter of fact, my 16" Colt M4 barrel measures a tad over 16" to closed bolt.  Others have measured very similiar, a tad over the advertised length.

That is common.  Usually it's 16.1 to 16.25.  It's my understanding the BATF has been a bit vauge oon the interpretation of the 16" rule.  If you need to have your barrel a minimum 16.0" in length or if 16.0" & under were NFA - while 16.01" and longer were non-NFA.  So everybody plays it safe and produces barrels that are a hair over 16".

Quoted: Any comments on this?

CMMG does theirs as a 14.7" w/perm. A2
RRA does theirs as a 15" w/perm. A2

Quoted: Quoted: Any comments on this?   CMMG does theirs as a 14.7" w/perm. A2 RRA does theirs as a 15" w/perm. A2

If that's the case, that probably explains why the barrels are the same length.  IIRC, DPMS makes CMMG's barrels, but chrome lines them.  Must be why my DPMS barrel is 16" with the A2 and crush washer.  It certainly doesn't have that extra washer that is in the picture above but I am 100% certain that it's 16" in length.  

Quoted: Have done two barrels like that: img.photobucket.com/albums/0603/Ekie12091941/aa19.jpg img.photobucket.com/albums/0603/Ekie12091941/aa25.jpg More pics here: ar15.com/forums/topic.html?b=3&f=118&t=231110 There is a large gap between the crown and the flash hider.  Ran one like that for over 10 years, and that combo was quite accurate (for what it was).  Suppose at some point you could get a bunch of carbon in there and have a problem? Seems to me the biggest draw back is that the flash suppressor is only threaded about 1/2 way onto the barrel.

is that discoloration from heat?

Quoted: is that discoloration from heat?

Why yes it is.  Normally I refinish, but I did not think that one looked that bad.