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Colorado 80 Percent Lower Laws

80 Percent Arms   |   Dec 6th 2021

Disclaimer: To get started, we want to share a small disclaimer. We are dedicated and proud supporters of everything 2nd amendment, but we are not lawyers. So, before you take what you read here and run with it, you will want to double-check all of your local or state gun laws. Make sure you are up to date on any special regulations that may apply to you and your situation. Gun laws are always changing and always do your part to stay up to date with the newest and current laws.

This information is provided as a service to the public. It is NOT intended to be taken as legal advice and should never be considered as such. Make sure to do your own research as you and you alone are responsible for your own actions.

This is a developing list of information we intend to update regularly to stay accurate and current. If you see a discrepancy or a mistake with your home state’s laws that we’ve covered, feel free to let us know so we can correct it. Thank you and stay safe!

What is an 80% Lower?

An 80% lower receiver is an unfinished and unserialized blank which requires some machining work from the end user to turn it into a 100% lower receiver, otherwise, what is legally considered as a firearm. 80 lowers are missing the trigger pocket and three holes that need to be milled and drilled out to be completed. Unless states have passed their own laws barring the possession or sales of 80% products; pending the ATF's updated decision from the most recent proposed rule 2021R-05 80% lowers are completely legal, not considered firearms and thus can be shipped straight to your front door. No FFL required. To explore the 80 percent lower receivers we have to offer, check out our multiple collections.

Are 80 Lowers Legal In Colorado?

As of this guide’s initial publish date, 80% lower receivers and frames are not considered as firearms by the ATF and are legal to ship directly to buyers residing in Colorado. While they may be legal per federal law, in June of 2021, Colorado reversed its preemption law which means that local governments can make their own gun regulations that are separate from the state law. Chances are, there may be some cities and localities that have banned certain firearms, parts and accessories or even 80 percent products. 

Do I Need to Serialize My 80 Lower in Colorado?

If you build out your own firearms starting with 80 lowers in Colorado you do not need to serialize the lower receiver or frame as there are currently no laws requiring citizens to do so. Should you wish to serialize your lower receiver we offer  custom engraving for our lowers.

Key Gun Laws in Colorado

Other than laws regarding 80 lowers, these are the key gun laws you should be aware of if you reside or are traveling through Colorado.

Firearm Possession and Purchase Requirements

In the state of Colorado, anyone the age of 18 years or older is eligible to purchase a long gun and anyone the age of 21 years or older can purchase a handgun. There are no permits or any extra identification documents required to purchase handguns in Colorado other than a driver’s license. All firearm purchases and private party transfers require a background check (Dealer Record of Sale also known as 4473 form or “DROS”). While federal law requires federal firearm license holders (“FFL’s”:) to initiate background checks on buyers prior to the sale of a firearm, federal law also allows states to serve as their own “point of contact” and conduct their own background checks via state, federal records or databases, as well as the option to use the FBI’s National Instant Criminal Background Check System (“NICS”) database. Colorado is a point of contact for the NICS and does have laws requiring firearms dealers to initiate the background check prior to transferring a firearm. However, Colorado uses their own system called the Colorado Bureau of Investigation or (“CBI”). The DROS process and the background check can take up to half an hour but buyers are allowed to take their firearms home the same day they purchase unless there is a flag in the system.

Open and Concealed Carrying

Colorado allows open carry in just about the whole state except for Denver county and persons must be at least 18 years of age and legally allowed to possess a firearm. Conceal carry weapon permits ,or “CCW’s,” are offered only to residents at least 21 years old but not non-residents. Colorado is a “shall issue” state. Be aware of the limits of open and conceal carrying by checking the state restrictions. To see which states’ concealed carry permits it honors check this reciprocity map here.

NFA Restrictions

Hunting with suppressors is currently legal. There isn’t a statewide assault weapons ban but certain cities in Colorado do have assault weapon bans (“AWB”) in place. However, not every city’s AWB ordinance is enforceable due to Colorado’s statewide preemption law.

Magazine Capacity Restrictions

There is a 15 round magazine capacity restriction in Colorado but NFA weapons and related items are unrestricted.

Mandatory Storage Requirements

Residents of Colorado should be aware of “safe storage” laws and mandatory firearm storage requirements in Colorado.


Colorado does have a Castle Doctrine law in place and the state does allow you to “Stand Your Ground.”

Ammunition Purchase

No state permit or background check is required to purchase any ammunition in Colorado nor are any records of ammo purchases kept. Under the Gun Control Act (GCA) ammo for shotguns and rifles can be sold to individuals 18 years of age or older. Any handgun ammo and online purchases of ammo shipped to Colorado requires buyers to be at least 21 years old.

Start Your Next 80 Lower Build with 80% Arms!

Generally speaking, Colorado residents are completely free to build their own firearms from 80 lowers and frames without any required serialization or FFL transactions. It's the perfect state to take advantage of your constitutional Second Amendment right and freedom to keep and bear arms. That includes 80% Arms! Grab a jig and some buddies to enjoy that freedom together and let us know if you need any advice with your build at any point in the process. Friends, live free.