It really depends on the market and location. Some states (ban states), they can bring $3000 and up easily as they are very restricted on what they can own. Other states, you are realistically looking between $1500-$2000, but that really depends on what buyers are willing to pay. I bought my 1977 Colt SP1 Sporter about 10 years ago for $1K. It looks like it has never been fired. That same rifle could, conceivably, sell for $1800-$2000 to the right buyer in most states. Colt's Reissue is reproduction of the early M16A1, not a SP1. There is quite a difference. If these SP1s were unfired and complete with their boxes and accessories, I would venture to say that you can add about $1500 more to their value. NIB Colt SP1s are worth quite a bit and quite a bit more if they are the early 1960s versions. Your SP1s are late production. I hope this helped.