How many SP1s do you have? When I’ve culled the herd (of a particular model) in the past I usually keep the nicest one. SP1s def do hold their value and prices have crept up slightly in recent years. Actually they seem to be the only ARs that have!
I only have one. Bought it new in 1978. When did the SP1 become a cult item? Seems like the tacticool ARs with 30 pounds of extras are all the rage.
Gun shops are filled with tacticool AR-15s that were bought in anticipation of a different outcome in the 2016 election and related fears of a ban. They are however not selling and those over stocked shops are marking them down to fire sale prices. Got a used AR-15 you want to sell without taking a bath? Good luck with that - unless you have an older pre-Ban Colt, or one of the even older SP1 AR-15s. They have held their value very well.
There are a few reasons for this:
1) The SP1 was the original AR-15.
It was the only game in town from January 2, 1964 until 1977 when Colt's patents expired and other companies started reverse engineering the AR-15 and selling their own versions. Olympic Arms was one of the first, but there are now scores of companies selling them.
However, there is still only one "Colt" and despite the company's faults, there is some residual brand appeal. There is also a collectibility aspect in having one of the early Colt made AR-15s.
The SP1 series production ended in 1982 when Colt started selling the revised Sporter II series, and the changes in that series reflected the competition from other companies now making copies.
2) Not everyone likes the M4geries, or worse, the tacticool carbines that the AR-15 has become.
The older pencil barrel, triangular handguard, A1 "Type D" or "Type E" stocked, original AR-15s have a great deal of retro appeal. So do the early 16" AR-15 carbines (introduced by Colt in 1977).
You can see evidence of this in the form of Brownells selling retro AR-15s. It's also evident in the form of the growing number of vendors who sell retro or new production retro style parts including retro upper and lower receivers for AR-15s.
Both are a direct response to the relative scarcity of the original Colt AR-15s and the desirability of the design.
Personally, I was issued the M16A1 and despite being raised with a M1/M14 bias, I liked the rifle. It was lightweight, very well balanced, and accurate (about 1.5 MOA with M193) - more than capable of hitting torso sized targets out to 400 meters under field conditions.
For that reason I gravitated toward the older AR-15s made along the same lines as the M16 and M16A1. I own a number of AR-15 variants, but my M16 and M16A1 clones (built on NDS receivers) are still the ones that get shot the most.
I'm also a fan of the slick side carbines, and again, they get a lot more range time than an M4gery.
Some of it is style preference but some of it is also just plain practicality. I have not shot a tactical rifle match in a few years, but I used to have a great deal of fun placing well up in the pack using a 16" lightweight carbine or an XM177E1 clone.
Way too many shooters take a reasonably lightweight M4gery and then load it up with railed forend and loads of tacticrap, turning it into a over weight, poorly balanced and slow "carbine" that weighs more than most rifles.
Some shooters are starting to discover or re-discover the benefits of a light and handy carbine or rifle and that's the niche the older Colts were made to fill.
3) The 1994 Assault Weapon Ban still has a lasting impact in some states.
In those states you still can't purchase a post ban AR-15, so the pre-1994 AR-15s (and magazines) bring a premium.
4) C&R eligibility
Despite the media hype, the AR-15 has been around a long time and in fact the civilian SP1 predated the M16's use by the US Army.
Civilian AR-15s entered the market on January 2, 1964, while the XM-16E1 didn't go into production until March 1964 and only 2,129 were delivered by the end of 1964, with only 57,240 produce in 1965. The XM-16E1 wasn't issued to infantry units until March 1965, it was not standardized as the M16A1 until February 1967, and it was not officially adopted until 1969, over 5 years after the SP1 entered production.
Consequently, the SP1 has been in production for 54 years now, and there are 4 years of AR-15 production that are now C&R eligible.