Does anyone know a collector's book, reliable publication or other source that traces the production changes of the SP1 year to year? I'm most interested in the late 60's to early 70's, like the butt stock change from Type D to Type E, the flash hiders from three prong to bird cage, barrel...

I own a 1981 Colt AR-15 SP1 chambered in .223. I was under the belief that you cannot shoot 5.56 ammo in this weapon without risk of damage to the firearm or personal safety. Recently, I had heard, (on YouTube...and I am not convinced,) that Colt is saying that though the AR-15 SP1 from this...

Dear Folks, Thank you for letting me join your forum. I hope to learn here. My interest is a new one for me, early SP-1's. Otherwise, I am active in my CMP club, shoot high power service rifle and match rifle and enjoy the occasional 1911 hard ball shoot. The only Colts I have these days...