btt

Quoted: just like the old days, nothing like some facts to end all the poo flinging.

I'll try to pay attention, but I've never noticed a connection.....(random smartass comment)

Quoted: Quoted: the bolt face to the muzzle that is the accepted method for measuring barrel length on most weapons.

Tweak I have a question I hope you can help me with

I have an 14.5 barrel with a pinned phantom FS.  After reading this thread about barrel lenghts I had the urge to measure the OAL of my barrel.  I used a cleaning rod and measured from the closed bolt to the end of the FS, I came out with 16.5".  I thought it would have been closer to 16".  I really don't care that it came to 16.5 but then I started thinking  

a phantom FS is 2 3/16" and an A2 FS is 1 3/4" it seems if I had an A2 perm attatched it would measure just over 16".  I know the barrel is supposed to be 14.5 but if it's measured from a closed bolt it's a little bit bigger.  Can you tell me what's the deal with that, would it be OK to put on an A2?, am I measuring wrong? does my math skills suck(which wouldn't be a shock)?

I'm hoping I'm not missing something and just making a complete ass out of myself with a stupid question

Quoted: Quoted: Umm. Las time I loked at W.H.B. Smith's  "Small Arms of the World", 11th edition, 1977, the XM177E1 was the smooth side recievered 11.5 inch barrel version, while the E2 was the forward assist version of the same piece. The early 10 inch (not 10.5 inch) barrelled piece was the XM177. Now you may know better than the book (edition edited by Edward Ezell), but until you can give me a source that contradicts mine, think I'll go w/the info I have. This is not correct.  Small Arms of the World is not correct with this.  Look at the Black Rifle or the drawings on SAW's website.

Yup. Actually, the "Small Arms of the World" edition I was quoting corrects itself a couple of pages later, in a listing of all the various AR15/M16 types, when it lists the E1 as the 10 inch barrelled forward assist type. When I went back to look at the picture of the 10 inch barrelled type it actually was the forward assist version.

That's what I get for only looking at the one paragraph

Quote from Tweak:

"taking your 1.75" for the A2 flash and subtracting the .63" for the muzzle shank leaves 1.12" for an OAL (from bolt face to end of A2 flash) of 15.729".

He needs to let me write down the measurements for him...

Tweak-

I'm late to the party, but I loved your post about barrel lengths...

I'm sure I mentioned it before, but it's a common mistake for people who do not know what they are doing to measure barrel length from muzzle to end of barrel extension.
Tweak's measurements all hold up from what I have found as well.

The safe number to subtract is 3/8" (getting less precise now) as the bolt face is 3/4" from the barrel torque shoulder and the extension is 1 1/8" long.

As mentioned, most commercial barrels are 1/4" to 1/2" longer than the manufacturer calls them.
Colt and Bushmaster usually run 1/4" longer.
I make all my barrels about 1/8" longer than 16" when requested, but I cut longer barrels within 1/16" of requested length.

Tom in Wa-
How did that barrel blank that I made for 'way back when' work out?

I once fixed a screwup caused by a "gunsmith" that did not take the barrel extension into account.
This gunsmith cut a 20" barrel down to exactly 16"
Using the typical measuring method of a cleaning rod down the bore against the bolt face, the barrel measures 15 5/8"
We never could get that barrel to run with it's original rifle length gas system.
Plugged the rifle port & added a carbine located gas port and hidden gas block and it works fine now...

If anyone needs barrels re-profiled, shortened, threaded etc, see www.ar15barrels.com/services.shtml

Randall Rausch

Quoted: I have an 14.5 barrel with a pinned phantom FS.  After reading this thread about barrel lenghts I had the urge to measure the OAL of my barrel.  I used a cleaning rod and measured from the closed bolt to the end of the FS, I came out with 16.5".  I thought it would have been closer to 16".  I really don't care that it came to 16.5 but then I started thinking   a phantom FS is 2 3/16" and an A2 FS is 1 3/4" it seems if I had an A2 perm attatched it would measure just over 16".  I know the barrel is supposed to be 14.5 but if it's measured from a closed bolt it's a little bit bigger.  Can you tell me what's the deal with that, would it be OK to put on an A2?, am I measuring wrong? does my math skills suck(which wouldn't be a shock)?

Tweak's mind works a little like mine, but he slipped and did the math for the muzzle device, not the whole barrel.
To more specifically answer WMHM4's question, do your math like this:

You have 16.5" now.
Subtract the 2.187 for the length of the phantom and you have 14.313 to the torque shoulder that the muzzle device tightens against.
Add the 1.75 for the A2 and you have 16.063"
You are a solid 1/16" over the legal minimum.
Note that I did not check actual component lengths, and the math above assumes your measurements to be correct.
Everyone has to do their own measurements before you take this advice and swap muzzle devices as your barrel may be different.

Randall

Quoted: no fair doing it the easy way Randall!

Ever hear of the phrase K.I.S.S?  

Randall

Quoted: this is odd, if I take his 16.5" barrel and subtract the 2.1875 for the Phantom then add the .63" muzzle shank I get a 14.9425" from bolt face to muzzle in contrast to the calculated (from the prints) 14.609" I can allow a little error to creep in given the slack between the lugs on the bolt and those on the barrel extension but no 0.3" worth.

Likely a commercial modification to the 14.5" military prints that stretched the barrel to about 15" so that an A2 comp will make it past 16" when permenantly attached.
As noted earlier, most commercial barrels run 1/4" to 1/2" longer than they are specified to be so your 0.3" variation is quite in-line with that.
They still call it a 14.5" because that's what the military uses and that's what all the mall ninjas want to buy!

Randall

Quoted: easy enough to find out, the length would have to added from the FSB forward (which I assume would affect the fit of the bayonet)

Probably a "ban period" barrel with no bayonet lug...
Of course lacking a bayonet lug also makes it hard to mount a bayonet.

Randall