Which would be a carbine version but with a pinned long tube flash hider..
A fellow at a gun show said he had one.
I googled and didnt find anything.

I dont think they did.

Not that I know of. Bushmaster made one a long time ago.

Guys at gunshows have all the cool stuff.

No.  They made a 16" carbine.  Lots of SP1 rifles were converted to "Commandos" replacing the stock and the barrels with aftermarket stuff.  When I was a dealer and gunshow vendor in the late 80s and 90s, I did this conversion for lots of SP1 owners.

I'd do it for $150, and I kept the stock group and barrel group on top of the $150. It gave me 20" Colt barrel groups and stock groups for builds I would later sell.  Often, they wanted a forward assist upper, so I would take their upper, and use a PWA upper with SGW barrel group.  SGW made better barrels than PWA, but PWA had better uppers.  I kept a stock of offset pins and accu-wedges to do the conversions.  I would coat the PWA upper with the grey spray on lube they retreated magazines and uppers with in the armory.

I have one it is listed as a Sporter ar15.

14.5 barrel with perm attached flash suppressor. Made in 1976 no fwd assist.

it is currently in the EE

I was told it is 100% factory

Probably a 653 or 654 barrel put on SP1. I have done that myself, back in the day, though the extra long flash hiders are a relatively new (way later than 1976) incarnation.  Colt would not make NFA items (14.5" barrel)  attached to civilian market SP1.  Military/LE weapons would have been 653 or 654 with that barrel.  You can contact Colt, and they can tell you what barrel that serial number had.

I would doubt very seriously that it is original. As was said, the SP1 Carbines and Sporter II Carbines came with 16" barrels. I would not have it listed for sale as being 100% factory until you have some conclusive documentation proving it. I do not think that you are going to get anything that will prove it to be a factory carbine. My feeling is that if you bought it from someone else that way, they most likely did not tell you the truth about it. I could be wrong, but I do not think so.

Anything Colt made based on a barrel shorter than 16" was an NFA weapon,
I don't care what that former-SEAL space shuttle door-gunner told you.



During the days of the original Model 6000/SP-1/Sporters, call it 1964 through 1978, Colt made two platforms only: 20" rifles at first, and then later on 16" carbines. Period.



Even later on through the early 80s some Sporters continued to be made until existing parts inventories were used up, so you'll see rifles marked "Sporter" but if it says MODEL SP1 it will have either a 16" or 20" barrel and a three-prong or A1 FH.

Other models such as the Sporter II were introduced, produced with large-hole forward assist A1 uppers and the original 1/12 barrel.

A  "Government Model" was produced with the "new" Government-profile barrel, at first with a large-hole A1 upper but soon moving to A2 as inventory ran out.

Along with that came a variety of HBARS, "Match" this or that, Sporter Lightweight Carbines, 9mm Carbines, 7.62 x 39 Carbines and so forth.

They even made accurized rifles with 24" barrels, but never anything with a barrel less than 16".



Remember the "Blue Label" guns? Colt was in such fear of the government and the media that they removed bayonet lugs from the rifles voluntarily, hoping to preempt being made to do so.

(Which worked out about as well as appeasement ever does.) Ask yourself: Would a company willing to do that kind of thing to avoid bad press make a gun using a short barrel, even with a pinned FH?



As time went by, especially after the A4s and M4s came out and people upgraded A1s to A2s, A2s to A4s and so on, some of those large-hole A1 uppers wound up on SP1s to give them that VietNam era look.

(Full disclosure: I did one of those myself, before I got into the 80% lower re-weld thing.)

But people being what they are, many of those were passed off as some kind of rare model or other.



Likewise, for quite a few years there was a LOT of surplus military stuff on the market, much if not most with Colt markings.

So, no big deal to take a 14.5" (or shorter) barrel, slap some kind of "commando" flash-hider on it and sell it as yet another secret-squirrel Colt model.

There was even a Commando-style flash hider that was bored out to fit over a 16" barrel to make it look like a Commando. I say "was" but I'm sure they're still out there.



But - Colt never made anything based on a 14.5" barrel, and never produced anything with a flash hider other than 3-prong, A1, A2 or no flash hider at all during the AWB.



Of course, Colt did (does) make a Commando model, but that's a short-barreled rifle intended for the military as US Property, or for law enforcement.

Legal for the peasantry to own as NFA SBW only.

Doubt it is a Colt.

The aftermarket  Commando / CAR 15 set ups were heavily pimped by the

various other manufacturers.

The main reason I have read, according to some, is you could get three 11.5" barrels out of

a 36" blank.

Colt didn't produce the carbine SP1 until 1977, yours started out as a rifle lower that someone converted.

Evidently, what he has is a bastardized Colt SP1 with very little value compared to an all original SP1 carbine.