Good choice with the Colt AR, the factory makes different models in different times of the year so it is like feast or famine, and guns are hot right now because of terror threats, gov possible ban, election year, etc, the gun factories can't keep up with the very high demand.
Sorry that your first Colt AR in the 1970s was not to your liking, my first ever centerfire rifle was a new Colt AR-15 Sporter SP1 with the same look as the Army's M-16A1 except it had no forward assist, I got it new in 1971 for a whopping $200 back then. It was my 3 years of saving from odd jobs, part time jobs and gifts from my family.
I was always into guns since I was a small kid, my father was a WW2 Army 11th Airborne veteran and I used his .22 bolt action rifle, and my .177 and .20 caliber pellet air rifles, a couple of years before I got my AR I was using his Colt Python, 1911 Gov't model .45, Browning Hi-Power 9mm, a very old beat up WW2 Walther P-38 9mm, S&W .22 LR target pistol, and Ruger .22 LR bull barrel target pistol.
My first Colt AR SP1 rifle was pretty good, it is so different than my father's, uncle's and my hunting rifles that's why I got attracted to it, also watching the movies and TV about the military.
In the early 70's .223 ammo was hard to find I could only get the more expensive imported Norma ammo but it was very accurate, I could group at 100 yd about 1" to 2", when there is a new Colt AR model I sold my old worn rifle and get the new model, so 45 years since my first AR I'm still at it because of the constant improvement of the AR platform.
I got my only one USGI M1 Garand (1950s Korean War made by International Harvester) from the DCM/ CMP back in 1986 and I used my new model then '86 Colt Sporter HBAR (heavy barrel) rifle for my first DCM rifle match which was a requirement to purchase the M1 Garand Rifle.
I was surprised I did very well on my first DCM match, I got 20th place out of 400 contestants during a 2 day weekend, maybe because I was also competing in NRA pistol and IPSC - USPSA combat pistol matches with a couple of years experience.
A long time ago past by since my first DCM match and I still remembered it was not perfect for me, I had two failure to feed on my second magazine load, first failure was the prone 600 yd then the second jam was the second prone 600 stage, I cleared both quickly and finished all my shots (rapid fire) before the cease fire, found out later I had a bad Colt 20rd mag.
Currently I have 5 Colt AR and one non Colt which is a Rock River Arms (RRA) commercial model 9mm carbine (but I will replace it later with a Colt 9mm carbine).
Model CE1000 Expanse M4 carbine
SP6920 Sporter M4 carbine
AR6721 AR-15A3 Tactical carbine HBAR heavy barrel
AR6721 AR-15A3 Tactical carbine with Rock Creek Barrels midlength gas system, medium contour barrel
MT6601 Match Target HBAR with USGI M16A2 Colt upper half
Just wait for the LE6940 to be available again sometimes this year, I heard it is a more accurate model and with AR it is like potato chips, nobody could only have just one.