It's tempting to treat Colorado's new ~900-model SSF guidance list as a checklist: find your rifle, and if it's not there, you're fine. That's not how it actually works, and the state's own guidance document says so directly.
What the guidance document actually says
Right in its introduction, the Firearms Dealer Division's guidance states that it's "based on the functional characteristics of the firearm identified in the definition of Specified Semiautomatic Firearms in section 18-12-116(1)(d), C.R.S." It goes on to specifically call out AR-pattern rifles (what the document calls "Modern Sporting Rifles" or MSRs) as "highly customizable" with "an unlimited number of configurations," and says plainly: "If the firearm, as configured, meets the specifications outlined in section 18-12-116(1)(d), C.R.S, it is included within this guidance document" — whether or not that exact configuration appears by name.
What that means practically
The legal test was never "is my exact manufacturer and model number printed on a state list." The test is the one written into the statute itself: is it a semiautomatic rifle or shotgun with a detachable magazine, or a gas-operated semiautomatic handgun with a detachable magazine — and does it avoid all of the statute's specific carve-outs (rimfire-only without a separate upper/lower, manual actions, permanently fixed low-capacity magazines, the named legacy-rifle list, and so on).
That means a home-built rifle, a small custom shop's build, or a mix-and-match parts gun assembled from several different companies' components can all meet the statutory definition even though none of them will ever show up as a distinct named entry on the state's list. The list is a reference tool built for the common cases — it isn't, and was never meant to be, an exhaustive or binding catalog.
What to do if you're genuinely unsure
Two options: reason it through against the actual statutory definition (rifle or shotgun, detachable mag, none of the listed exceptions apply), or use the state's formal process for getting an official answer — see our companion post, How to Challenge Whether Your Firearm Is Really an SSF, for how that works.
As always, we are not lawyers — just Colorado citizens trying to understand the new law and share what we learn. The information on this website is for general informational purposes only and does not constitute legal advice, nor does it create an attorney/client relationship. The accuracy, completeness, or currency of the content is not warranted. Your use of content on this website is at your own risk. Consult an attorney about your specific circumstances.