I have a lot of spare parts and I believe I may have enough to build a GUU clone. Here is the rundown.

Slick side upper
CAR type stock
Lower with mag release fence
M4 barrel with birdcage
A1 grip

It seems like an old CAR 15 with an M4 front end. Is that an accurate description?

I have used the search function, and I still would like additional info.

Such as, What does the GUU mean?

Pics or any history on this odd variant would be appriciated.

USAF EOD

GUU-5 series W/ CATM upgraded M-4 bbl and upper.

en.wikipedia.org/wiki/Colt_Commando

Scroll down to a table marked "Related Models"  you'll see most of the basics

What does the 'GAU' in GAU-5P stand for?

I was a cop in the Air Force and carried one daily for a couple years.  I was always told it stood for 'Government-Altered Unit.'  Never saw it in writing as I recall, but that's what I consistently heard.  They weren't consistently altered, though.  I saw every barrel length, flash-hider type, receiver markings, etc..  I was only ever issued one that wasn't just a mish-mash of parts.

Google found this: answers.google.com/answers/threadview?id=706265

Got my hands on one for an exercize with blanks.  Was fun because it fired auto, instead of 3 round burst.  But that thing was a bitch when it got dirty.............it didn't have a foward assist.  Blanks fowl things up quick......

I thought I read somewhere that GAU stood for " Gun Automatic Universal".

GAU is an acronym for "Gun-Aircraft Unit"

I used to spend time inside an M61A1, but that was years ago!

Quoted: GAU is an acronym for "Gun-Aircraft Unit" I used to spend time inside an M61A1, but that was years ago!

Great info, but what about GUU

This thread has gone on this long and NOBODY's referenced the

Colt Military Carbine Technical & Historical Guide ??

I'm building a GAU-5P using the information in it from Capt Richardson, Ekie, and Scottryan.

johnreilly, thanks for clearing that up.

Quoted: GAU is an acronym for "Gun-Aircraft Unit" I used to spend time inside an M61A1, but that was years ago!

I always heard it as Ground Assaut Unit.

-k

Based on my research here is what I have got:

USAF GAU & GUU Designations,
I have seen and heard a number of explanations for the GAU designation. I believe JohnReilly got the original designation correct, “Gun Aircraft Unit”. If you search the USAF inventory you will find other GAU designations, and they all refer to aircraft based weapons. So how did it go from referring to aircraft weapons to AR Carbines, I have no idea! I have heard that when it was used to refer to an AR Carbine, that it was commonly referred to as “Gun Automatic Unit”. However, I have also heard it referred to as Gun Assault Unit and Gun Air Force Unit. This thread is the first time that I have heard, Govt. Altered Unit, Gun Automatic Universal, and Ground Assault Unit.

So if that covers the GAU designation, what about the GUU designation? I have no real clue! I have heard Gun Universal Unit, but I can not confirm that with any USAF documentation.

On the specs for a GUU-5P,
There is really not a specific spec, in reality you will find a lot of variations that fall under the GUU-5P designation. Typically a GUU-5P will have:
Lower – Older A1
Buttstock – can be anything from the original aluminum, to one of the newer plastics
Receiver – could be an original slabside, or a later model with the fence
Piston Grip – could be the original A1, or an updated A2

Upper – Anything Goes, I have seen just about every possible configuration
A1 – with or without Forward Assist, Flat or Tapered Slip Ring, Older or Newer Carbine Handguards, A2 or M4 Barrel
A2 – with Forward Assist, with Tapered Slip Ring, Newer Carbine Handguards, A2 or M4 Barrel
M4 – Flattop (no carry handle), with Forward Assist, with Tapered Slip Ring, M4 Handguards, M4 Barrel

If you check the Guide as Forest pointed out you should be able to find some more info.

Below are also some pics:






Good luck with the build, make sure you post some pics when you are done.
"Capt Richardson"

To what USAF prefixes actually mean, most sources say that GAU is Gun, Aircraft Unit, which follows most USAF prefix conventions.  GUU would, in my opinion, likely stand for Gun, Universal Unit, as the only two GUUs I know of are small arms, and the GAU-5 is the only non-aircraft gun with a GAU prefix.

Quoted: To what USAF prefixes actually mean, most sources say that GAU is Gun, Aircraft Unit, which follows most USAF prefix conventions.  GUU would, in my opinion, likely stand for Gun, Universal Unit, as the only two GUUs I know of are small arms, and the GAU-5 is the only non-aircraft gun with a GAU prefix.

Seems like it would be more like Government Unofficial Unit.

Anyone know any USAF Armorers we can get conformation from?

Why would it be unofficial?

Quoted: GAU is an acronym for "Gun-Aircraft Unit" I used to spend time inside an M61A1, but that was years ago!

GAU is a standard AF designation for weapons in general, both individual and aircraft. When I was active duty, we ordered replacements for individual weapons and had 2 each 7.62N guns for an A model AC130's delivered. They had very close FSN/NSN number at the time.

I'm confused by your statement.  I'll say right now that I am easily wrong, but I fail to understand how you reach your conclusion.  FSN/NSNs of what individual weapons were close to what at the time?  I still only know of one GAU that is a personal weapon, and all GUUs I know of are personal weapons, which is in my mind, why the GUU prefix was created.

Quoted: I'm confused by your statement.  I'll say right now that I am easily wrong, but I fail to understand how you reach your conclusion.  FSN/NSNs of what individual weapons were close to what at the time?  I still only know of one GAU that is a personal weapon, and all GUUs I know of are personal weapons, which is in my mind, why the GUU prefix was created.

Thatguy96,

As I stated when I was assigned at Hurlburt ('73-'79 for context), GAU was the common prefix whether it was for an individual weapon or 7.62N/20MM AC-130 gun (depending on A and H models) at the time. Tht only exception, IIRC was the 105 for the H models. We ordered replacement weapons (individual) and received A model mini-guns. They all had a GAU designation at that time (similar FSN/NSN). We had one hell of time returning them back to supply and getting what we ordered.

Quoted: Why would it be unofficial?

Because the configurations are all different.

And it is still Unknown what GUU stands for

Quoted: Quoted: I'm confused by your statement.  I'll say right now that I am easily wrong, but I fail to understand how you reach your conclusion.  FSN/NSNs of what individual weapons were close to what at the time?  I still only know of one GAU that is a personal weapon, and all GUUs I know of are personal weapons, which is in my mind, why the GUU prefix was created. Thatguy96, As I stated when I was assigned at Hurlburt ('73-'79 for context), GAU was the common prefix whether it was for an individual weapon or 7.62N/20MM AC-130 gun (depending on A and H models) at the time. Tht only exception, IIRC was the 105 for the H models. We ordered replacement weapons (individual) and received A model mini-guns. They all had a GAU designation at that time (similar FSN/NSN). We had one hell of time returning them back to supply and getting what we ordered.

Okay, that clears it up.  Still, there is only one individual weapon to my knowledge with a GAU prefix.  

And the U is still unknown, but I would still say that unofficial is not likely because there is only one configuration of the GUU-4/P.

GAU = Gun Automatic universal. dot

The A is not "aircraft". Its listed that way in all the dictonaries/ indexes we have. GUU is not listed in anything I've seen. I will do more research.

Nearly all guns in the AF have the GAU designation, even if they are on fighters or not.

Here in lies the problem with the GUU Designation,
I have spoken to both past and present USAF CATM and Unit Armorers, and none of them can give me a consistent answer on the GUU Designation. None of them can also provide me with any USAF documentation that explains what GUU stands for. To be honest, most of them also really don't care what GUU stands for.


In regards to the GUU Rebuilds,
I also forgot to mention that in addition to using GAU-5A, GAU-5AA, and GAU-5P Lowers to make GUU-5P's, the USAF also likes using M16 Lowers to makeup GUU Carbines. The picture below shows 3 GUU's that were all built using M16 Lowers.



If anyone can get, or has, any "Official USAF" documentation on the USAF Carbines please share it.

Thanks,
"Capt Richardson"

captrichardson pretty much sums up what I have seen with the GUU-5Ps.  The ones we have are M16s with A1 uppers rebarreled with M4 barrels and old style metal CAR stocks added.  I have seen slab side uppers and lowers and some with A2 uppers as well.  Some look like I put the thing together in the garage while others look really well done.  I will ask one of our CATM guys about the designation tomorrow.  He may not know since he is just filling in for NCOIC while he is deployed.  I am sure if I keep asking someone will know.

Well, at 0015 in the morning I can't really make alot of sense out of this but I believe the answer lies here.

Designations Of U.S. Aeronautical and Support Equipment



ETA: Reading through this again this morning I believe that GAU stands for GAU-  Guns Airborne, Unit. And GUU simply stands for Guns, Unit. Does anyone else read it this way?

I just spoke to an engineer for the USAF small arms program today from Warner Robins AFB about the GAU/GUU.  Here is his input on it.

The GAU stands for Gun Automatic Unit.
The GUU was a total F-up.  When the AF wanted to redo its short carbine setup in the early 80's the Army didn’t want to have anything to do with it.  They had no need for a short barreled gun.  The AF has to go through the Army for all its small arms.  So they told the AF to get a hold of Colt for a prototype.  When it was all said and done they got the approval for the 14.5" pencil barrel 1-7 twist.  When the Technical Manual was written the writers used GUU instead of GAU.  They had several hundred manuals printed already.  So to save money they used the term GUU-5P instead of reprinting the manuals to GAU-5P.  When I asked if they made a name to fit the GUU designation he said no.  Its just meaningless letters, he was just happy they didn’t print GAY since Y is right next to U on the keyboard.  (He started laughing hysterically at his joke)  The AF took a stockpile of M-16's and sent them to Anniston Arsenal for rebuild/re-barreling.  They would use whatever parts were on the original M16 and replace whatever was not serviceable.  He is supposed to get me some printed history and some Tech Manuals he has.  Again this is from an Engineer in the USAF small arms program of 25+ years.  

Quoted: I just spoke to an engineer for the USAF small arms program today from Warner Robins AFB about the GAU/GUU.  Here is his input on it. The GAU stands for Gun Automatic Unit. The GAU was a total F-up.  When the AF wanted to redo its short carbine setup in the early 80's the Army didn’t want to have anything to do with it.  They had no need for a short barreled gun.  The AF has to go through the Army for all its small arms.  So they told the AF to get a hold of Colt for a prototype.  When it was all said and done they got the approval for the 14.5" pencil barrel 1-7 twist.  When the Technical Manual was written the writers used GUU instead of GAU.  They had several hundred manuals printed already.  So to save money they used the term GUU-5P instead of reprinting the manuals to GAU-5P.  When I asked if they made a name to fit the GUU designation he said no.  Its just meaningless letters, he was just happy they didn’t print GAY since Y is right next to U on the keyboard.  (He started laughing hysterically at his joke)  The AF took a stockpile of M-16's and sent them to Anniston Arsenal for rebuild/re-barreling.  They would use whatever parts were on the original M16 and replace whatever was not serviceable.  He is supposed to get me some printed history and some Tech Manuals he has.  Again this is from an Engineer in the USAF small arms program of 25+ years.

Very cool info!  Sounds like a typical military SNAFU .  Reminds me of why the Blackbird spy plane is called SR71....Pres Eisenhower mistakingly referred to it as the SR71 instead of it's correct name RS71 so they didn't want to correct him so they simply re-named it.

So the GUU designation was merely a misprint in a manual, so they they just went with that?

Odd.

Quoted: I just spoke to an engineer for the USAF small arms program today from Warner Robins AFB about the GAU/GUU.  Here is his input on it. The GAU stands for Gun Automatic Unit. The GAU was a total F-up.  When the AF wanted to redo its short carbine setup in the early 80's the Army didn’t want to have anything to do with it.  They had no need for a short barreled gun.  The AF has to go through the Army for all its small arms.  So they told the AF to get a hold of Colt for a prototype.  When it was all said and done they got the approval for the 14.5" pencil barrel 1-7 twist.  When the Technical Manual was written the writers used GUU instead of GAU.  They had several hundred manuals printed already.  So to save money they used the term GUU-5P instead of reprinting the manuals to GAU-5P.  When I asked if they made a name to fit the GUU designation he said no.  Its just meaningless letters, he was just happy they didn’t print GAY since Y is right next to U on the keyboard.  (He started laughing hysterically at his joke)  The AF took a stockpile of M-16's and sent them to Anniston Arsenal for rebuild/re-barreling.  They would use whatever parts were on the original M16 and replace whatever was not serviceable.  He is supposed to get me some printed history and some Tech Manuals he has.  Again this is from an Engineer in the USAF small arms program of 25+ years.

I knew the item manager for USAF small arms was at Robbins. When I was TDY there I wanted to go over and pick his brain, but I never got the chance.

What these guys say is the definitive answer as far as the AF is concerned. I hope he comes through with the printed history.

All the same... somebody will still show up and fly the BS flag because you can't supply a chapter and verse reference over the net.  

i also noted as the engineer was speaking is how he refered to the guns.  insted of saying G-A-U individually he said it as a word- GOW as in WOW. and for GUU - GOO as in the Goo Goo Dolls

Quoted: So the GUU designation was merely a misprint in a manual, so they they just went with that? Odd.

Not for the military, not by a long shot!

Finally, typical “Military Wackiness”, that could makes sense out of nonsense.

If you check out the Military Documentation for Designations (Quib posted a good link), you will find that GAU works out to be Gun Automatic Unit, and there are other USAF GAU designations. If you check for the GUU designation, you will find that it makes no sense and there are only 1 or 2 GUU designations. Would I buy that GUU came about as a result of “Military Snafu”, so far that explanation is as good as any of the others that I have heard. Having said that . . .

. . . some additional food for thought,
The first round of GAU’s, the GAU-5A and GAU-5AA both would have been built with a barrel that had a 1/12 twist rate. When those 10” and 11.5” barrels were replaced with 14.5” barrels, they would have also initially been replaced with barrels that had a 1/12 twist rate. Eventually the replacement barrels would have had a 1/7 twist rate. One explanation that I got for the GAU and GUU designations was that the GAU designation was initially given to Carbines that were rebuilt with the 14.5” barrel with the 1/12 twist rate, and the GUU designation was given to Carbines that were rebuilt with the 14.5” barrel with the 1/7 twist rate. The difference in designations was so that you could easily tell if you had a 14.5” barrel with a 1/12 or 1/7 twist rate.

Machinehead,
You have access to a VERY VALUABLE RESOURCE, please get us any and all info that you can. I have talked to USAF folks from Spec Ops, CATM, and Material Command, and I have not really gotten very far on the origins and meanings of the GAU-5P and GUU-5P designations. I have gotten multiple explanations based on "personal memories", but I could not get any solid USAF written documentation. Anything that you can get in writing would be great.

It would really be great to finally get to the bottom of this!

Thanks,
“Capt Richardson”

The only reason I would doubt this story is the existance of the GUU-4/P designation, which came before the GUU-5/P designation came into existance, at least to my knowledge.

i just did a quick search of GUU-4/p and got very litle info from it.  from what i got it was an experamental version with a .221 fireball.  looks like i will be talking with the engineer some more on this.  

i just found a holster for a .38 revolver that is labled GUU-1/P.  
www.ljmilitaria.com/weapons__sheaths__holsters__and_etc_.htm

The GUU-4/P is the Colt arm gun in .221 Fireball.

Well NONE of the CATM guys in my unit have any idea what GAU or GUU stand for.  From everyone elses experience I am not suprised.

A few more GUU pics.

Hey CH139,

Thanks a Million, those are some really great pics!

Sorry to be a pain, but could you please see if you could answer some of the questions below.

Quoted: A few more GUU pics. CARBINE #1 photos.templarfirearms.com/albums/userpics/10001/normal_gau_03.jpg   Is this an A1 Barrel (.625 with an A1 Flashhider) or an A2 Barrel (.750 with an A2 Flashhider)? Was this Lower actually remarked GUU-5P? Very interesting, this is a great example of a true "USAF Mixmaster FrankenCarbine". The Lower is A1, but it has an A2 Grip, the Buttstock is New, the Upper is A1, but it has a FA and BD, the Slipring is Flat. This is a total parts rebuild. -------------------------------------------------------------------------------------------- CARBINE #2 photos.templarfirearms.com/albums/userpics/10001/normal_gau_05.jpg CARBINE #2 (photo 2?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_06.jpg Which one of the Carbines pictured do these markings belong to (is it the one picture above)? Any chance of getting a partial Serial Number, like the first 4 digits? This is a USAF M16 Lower, that has been used to rebuild a GUU Carbine. CARBINE #2 (photo 3?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_08.jpg Is this photo the reverse side of the one pictured above? If so this confirms that this was a USAF M16 that has had the A1 Buttstock replaced with a Newer Collapsing Stock, and the "Front End" has been rebuilt using a combination of Old (Slipring & Handguards) and New (Barrel) parts. -------------------------------------------------------------------------------------------- CARBINE #3 photos.templarfirearms.com/albums/userpics/10001/normal_gau_09.jpg Is this an A1 Barrel (.625 with an A1 Flashhider) or an A2 Barrel (.750 with an A2 Flashhider)? Was this Lower actually remarked GUU-5P? CARBINE #3 (photo 2?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_11.jpg Do these markings belong to the Carbine pictured above? CARBINE #3 (photo 3?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_13.jpg Is this the flipside of the Carbine pictured above? -------------------------------------------------------------------------------------------- CARBINE #4 photos.templarfirearms.com/albums/userpics/10001/normal_gau_14.jpg Is this an A1 Barrel (.625 with an A1 Flashhider) or an A2 Barrel (.750 with an A2 Flashhider)? Was this Lower actually remarked GUU-5P? CARBINE #4 (photo 2?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_15.jpg Do these markings belong to the Carbine pictured above? CARBINE #4 (photo 3?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_16.jpg Is this the flipside to the one pictured above?

Thanks again for the great photos, and thanks in advance for answering the questions if you can.
"Capt Richardson"

Quoted: A few more GUU pics. photos.templarfirearms.com/albums/userpics/10001/normal_gau_03.jpg   photos.templarfirearms.com/albums/userpics/10001/normal_gau_05.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_06.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_08.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_09.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_11.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_13.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_14.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_15.jpg photos.templarfirearms.com/albums/userpics/10001/normal_gau_16.jpg

Nice pics! Very similar to two of my builds!

Quoted: Quoted: So the GUU designation was merely a misprint in a manual, so they they just went with that? Odd. Not for the military, not by a long shot!

The SR-71 was supposed to be called the "RS-71," but President Johnson, in his announcement of the aircraft at a press event said it wrong.  So the designation was changed to SR because that's what the President said.  There are goofier things in our military history, folks.  Changing from "GAU" to "GUU" because of a misprint in already-printed manuals is small potatoes compared to some things!

P.S., for other types of equipment, the Joint-Army/Navy nomenclature conventions work very well for decoding a nomenclature.  They're codified in MIL-STD-196E.

I think it was President Eisenhower, could be wrong though.
MMMM.... further research says you are correct, but other sources say LeMay switched it to SR71 just days before Johnson was giving a speech about it...The press got copies of the speech without the correction and thought LBJ flubbed it.

I found a good explanation of the USAF munitions naming system: www.aerospaceweb.org/question/weapons/q0166.shtml

Format of names are "xx x - # x / x"

The first 2 letters are the type of munition (cluster bomb, rocket etc)and the 3rd letter is for the category of equipment (group, component or unit).

GAx = Airborne Gun
GUx= Miscellaneous Gun (other than airborne)

xxU = Unit - A piece of equipment that can function on its own.

The number after the dash is the series number (the xth type of GAU), the next letter is the series model (revision?), and the last letter is the installation designator (how the unit is installed, carried, or otherwise employed).

P = carried by an individual person

GUU-5/P would be Miscellaneous Gun, Unit, Series 5, Personal
GAU-5A/A would be Airborne Gun, Unit, Series 5, Revision A, Aerospace vehicle fixed


My theory for GAU, etc is that the naming system did not have a way to describe the carbines when they were introduced. It probably goes back to the prototype Survival Rifle, and they called it an airborne gun since it was supposed to stay in the plane until a crash. The USAF kept the GAU prefix for continuity even though the carbine evolved from a pilot's survival rifle into a weapon for ground based forces. Eventually all of the USAF frankensteined mutts were grouped together under the GUU-5/P category for simplicity because it was impossible to keep up with the GAU-5x/x variations.

My question: Why is it GAU-5A/B ? Shouldn't the second revision be GAU-5B/A under this system?

ETA: Pic of my GUU-gery

Quoted: <snip>and the GUU designation was given to Carbines that were rebuilt with the 14.5” barrel with the 1/7 twist rate. The difference in designations was so that you could easily tell if you had a 14.5” barrel with a 1/12 or 1/7 twist rate.<snip>

Capt.

FWIW, My unit had GUU-5P's with 1/12, 14.5" bbls for many years before the USAF started converting to 14.5, 1/7 bbls.

Quoted: My theory for GAU, etc is that the naming system did not have a way to describe the carbines when they were introduced.

It may be different.  I first saw the term "GAU" in the mid-70's.  I had seen the carbines before then, just didn't know what the official designation was.  It's entirely possible that an aircraft term was used to disguise the fact that the USAF was procuring or making small arms rather than taking VN era hand-me-downs from the Army.  The XM-177 series were not renowned for their reliability.  USAF later did get some ex-Army weapons.  I saw one with a forward assist at Malmstrom AFB ca. 1982 or so.

T-Money,
Thanks for the additional help and explanations with the USAF designations. That was the first time that I had seen many of those designations explained in that manner in a written reference. That would kind of throw out, or eliminate, the theory that the "GUU" designation was simply the result of a typo or snafu.

On the 5A/B or 5B/A, good luck getting that one sorted out. I have seen it listed both ways in various references. I have never been able to nail that one down, there are to many variations and conflicting descriptions. The one rumor/explanation that seemed to be the most popular for the A/B or B/A designation is that it was given to some XM177E2s that were donated/transferred from the US Army to the USAF following Vietnam. I have seen photos of USAF personnel with what should have been a USAF GAU-5AA, excpet that it had a forward assist. Edlmann’s description could also confirm this. Personally, I am hoping to get something more solid, but I am also not holding my breath.


BMick325,
Were the rebuilds with the 14.5" Barrels that had the 1/12 twist rate marked GUU-5P or GAU-5P?
By chance do you know if they were rebuilt and remarked at the Unit Level or at the Depot Level?

I ask because if they were rebuilt and remarked at the Unit Level, anything goes. I have seen so many variations in how the markings were done at the Unit Level that there are obviously some serious variations and inconsistencies. I have seen GUU5P, GUU-5P, and GUU-5/P. The photos that I posted earlier show a lot of that variation.

Were those GUU-5P's built using a USAF M16 Lower and/or Upper, or were they built off of an existing GAU-5A or GAU-5AA Carbine?

Every GUU-5P that I have handled has had a barrel with a 1/7 twist rate. They have included both A2 (.750" with A2 Flashhider) and M4 profiles (.750" with A2 Flashhider, and step cut for M203). However I can not rule out that an earlier GUU-5P could have also had a barrel with the 1/12 twist rate.

I have never actually put my hands on a GAU-5P yet, I have only seen photos, and heard descriptions. In all of those cases they were 14.5" barrels with 1/12 twist rate and an A1 profile (.625" and an A1 Flashider).

Another explanation that I have heard for the GAU versus GUU designation was that the GAU designation was used when an existing GAU-5A or GAU-5AA was rebuilt, and the GUU designation was used when anything else was rebuilt such as a USAF M16. For the most part I have found that to hold true, but I have seen 1 example where a GAU-5AA was rebuilt and remarked GUU5P, however it was also a Unit Level “Hack Job” so it may have simply been a mistake.

To be honest, I am not real sure that we will ever really get to the bottom of this with 100% certainty, but it has been fun (and frustrating) trying, and I have learned a lot.

Thanks again to everyone for all of the help and input,
"Capt Richardson

PS: another rumor floating around is that the GAU-5P designation was actually given to the Colt Model 653. I have confrimed that the USAF did have Colt Model 653's in inventory, but I have not been able to confirm if they were actually designated GAU-5P.

So the mystery continues!

t-money, very authentic looking GUU forgery. 14.5-inch SBR?

I’ll answer these as best I can. I (unfortunately) didn’t take the pics or get to handle the weapons, just ordered the pics.

For what it’s worth.

Quoted: Hey CH139, Thanks a Million, those are some really great pics! Sorry to be a pain, but could you please see if you could answer some of the questions below. Quoted: A few more GUU pics. CARBINE #1 photos.templarfirearms.com/albums/userpics/10001/normal_gau_03.jpg   Is this an A1 Barrel (.625 with an A1 Flashhider) or an A2 Barrel (.750 with an A2 Flashhider)? Not sure, but I believe it is the thinner LW barrel, A1 flash hider, and marked only as M16 Was this Lower actually remarked GUU-5P?Don’t think so. Very interesting, this is a great example of a true "USAF Mixmaster FrankenCarbine". The Lower is A1, but it has an A2 Grip, the Buttstock is New, the Upper is A1, but it has a FA and BD, the Slipring is Flat. This is a total parts rebuild. -------------------------------------------------------------------------------------------- CARBINE #2 photos.templarfirearms.com/albums/userpics/10001/normal_gau_05.jpg CARBINE #2 (photo 2?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_06.jpg Which one of the Carbines pictured do these markings belong to (is it the one picture above)? I believe it is the No. 2 pic, the weapon with the M4 barrel and A1 grip. Any chance of getting a partial Serial Number, like the first 4 digits? I’ll see if I can find it. This is a USAF M16 Lower, that has been used to rebuild a GUU Carbine. CARBINE #2 (photo 3?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_08.jpg Is this photo the reverse side of the one pictured above? I don’t know if it is or not. It looks very similar, but the slipring is much more worn than the first pic. If so this confirms that this was a USAF M16 that has had the A1 Buttstock replaced with a Newer Collapsing Stock, and the "Front End" has been rebuilt using a combination of Old (Slipring & Handguards) and New (Barrel) parts. -------------------------------------------------------------------------------------------- CARBINE #3 photos.templarfirearms.com/albums/userpics/10001/normal_gau_09.jpg Is this an A1 Barrel (.625 with an A1 Flashhider) or an A2 Barrel (.750 with an A2 Flashhider)? Believe it is the thinner barrel Was this Lower actually remarked GUU-5P? Yes CARBINE #3 (photo 2?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_11.jpg Do these markings belong to the Carbine pictured above? Yes CARBINE #3 (photo 3?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_13.jpg Is this the flipside of the Carbine pictured above? Yes -------------------------------------------------------------------------------------------- CARBINE #4 photos.templarfirearms.com/albums/userpics/10001/normal_gau_14.jpg Is this an A1 Barrel (.625 with an A1 Flashhider) or an A2 Barrel (.750 with an A2 Flashhider)? Was this Lower actually remarked GUU-5P? No CARBINE #4 (photo 2?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_15.jpg Do these markings belong to the Carbine pictured above?Yes CARBINE #4 (photo 3?) photos.templarfirearms.com/albums/userpics/10001/normal_gau_16.jpg Is this the flipside to the one pictured above? Yes Thanks again for the great photos, and thanks in advance for answering the questions if you can. "Capt Richardson"

Quoted: ETA: Pic of my GUU-gery i29.photobucket.com/albums/c286/turnerhicks/Misc/IMG_0686.jpg

Nice build and nice pic!  

Quoted: GAx = Airborne Gun GUx= Miscellaneous Gun (other than airborne) xxU = Unit - A piece of equipment that can function on its own. The number after the dash is the series number (the xth type of GAU), the next letter is the series model (revision?), and the last letter is the installation designator (how the unit is installed, carried, or otherwise employed). P = carried by an individual person GUU-5/P would be Miscellaneous Gun, Unit, Series 5, Personal GAU-5A/A would be Airborne Gun, Unit, Series 5, Revision A, Aerospace vehicle fixed

Excellent.

Your weapon is exactally what I was wanting to build.

Thank you for the info and great pic.

Quoted: t-money, very authentic looking GUU forgery. 14.5-inch SBR?

Nope, 14.5 with perma-soldered Sabre Defence extended A2 to just over 16 total.

Weighs slightly less than 5.75 lbs without a mag. I also used the more useful (IMHO) A2 aperture instead of the A1.

Thanks for the compliments.

Quoted: BMick325, Were the rebuilds with the 14.5" Barrels that had the 1/12 twist rate marked GUU-5P or GAU-5P? By chance do you know if they were rebuilt and remarked at the Unit Level or at the Depot Level?

GUU-5P

Not sure of exact wording of the markings on each carbine. AFIK, All were unit level builds.

Were those GUU-5P's built using a USAF M16 Lower and/or Upper, or were they built off of an existing GAU-5A or GAU-5AA Carbine?

Some were built off of M-16 lowers. My unit had a shortage of GUU's for years and finally got the authorization to convert some excess M-16's to GUU's.

Every GUU-5P that I have handled has had a barrel with a 1/7 twist rate. They have included both A2 (.750" with A2 Flashhider) and M4 profiles (.750" with A2 Flashhider, and step cut for M203). However I can not rule out that an earlier GUU-5P could have also had a barrel with the 1/12 twist rate.

Our  squadron's M-16's and GUU-5's were converted in 1999 or 2000 to 1/7 barrels. Up until then they were all 1/12. The GUU's got the M-4 profile bbl with a fixed handle A2 upper. I was pissed about the deal because 2 of our weapons that got converted to GUU-5's were minty 601's that I was trying to keep in original configuration.

I think the only consistency I have seen with the GUUs is the straight sided slip ring; have yet to see one with a delta ring.