The statute exempts it. The state’s own final guidance excludes it. The manufacturer
was asked to confirm how it’s built. The answer at the counter was still no — and
“regardless of what HK says.” This is what the law does in the real world.
On August 25, 2026 — three and a half weeks after SB25-003 took effect
— a Colorado buyer tried to purchase a Heckler & Koch MP5 .22 LR from a
licensed dealer in Colorado. Not the 9mm submachine-gun clone: the rimfire replica, made by
Umarex/Walther under HK license, chambered only in .22 Long Rifle. A plinker.
By the letter of the law, this gun is not covered. By the state’s own published
list, this gun is not covered. He couldn’t buy it.
What follows is the exchange, lightly condensed, with names and identifying details removed. The
dealer is a real licensed store. The compliance manager is a real person doing a real job with real
criminal exposure. Nothing here is meant to shame them — that is the point. The law put them in
this position.
The Law, in One Sentence
SB25-003 — now C.R.S. § 18-12-116 — says a “specified
semiautomatic firearm” does not include:
“A firearm designed to accept, and capable of operating only with, .22 or
lower caliber rimfire ammunition, unless the firearm has a separate upper and lower
receiver.”
Two prongs. Rimfire-only: the MP5 .22 is. Separate upper and lower receiver: the MP5 .22 is built
the way every MP5 is built — a single receiver with a removable trigger pack (the
fire-control module that slides out for cleaning). That is not an AR-pattern upper/lower. The
serialized firearm is the receiver; the trigger pack is a part.
The State Already Sorted This Gun
The Department of Revenue published a guidance list of covered models. Between the
May 15, 2026 draft and the July 1, 2026 final, the state applied the
receiver test to the .22 replicas — and its choices are unmistakable:
Removed from the final list: the HK MP5 captioned .22 LR, and the
Walther-made HK G36 .22 LR — both single-receiver HK-pattern guns.
Kept on the final list: the Walther/Colt M4 Carbine .22 LR — an AR-pattern
replica that genuinely has a separate upper and lower. That is the “unless” clause
doing exactly what it says.
The surviving “HK MP5” entry on the final list is the centerfire
variant, captioned “(Semi-Auto) (SBR).” The .22 was specifically taken off. It is easy to
read past on a quick scan — which turns out to matter.
The statute asks two yes-or-no questions. Here is the MP5 .22 LR walked through
them — next to the AR-pattern .22 the state kept on its list, so you can see the line
the law actually draws.
The state’s July 1, 2026 final list matches this graph exactly: the AR-pattern .22 stays on;
the MP5 .22 LR comes off. The dealer’s reading puts the MP5 in the right-hand box on the strength
of a word in a manual — not a takedown pin.
Six reasons the MP5 .22 LR is not a “specified semiautomatic firearm.”
1. It passes prong one on its face. The MP5 .22 LR is designed for, and can
only operate with, .22 Long Rifle rimfire. There is no centerfire conversion; the bolt, barrel, and
magazine are rimfire-only. The statute’s exclusion begins with this gun.
2. It has one receiver, not two. Like every MP5-pattern firearm, the frame is a
single receiver that houses the barrel, bolt, and trigger mechanism. Nothing “separates”
into an upper and a lower; a trigger pack slides out of one receiver for cleaning. That is a
part, the same way a bolt or a magazine is a part.
3. Federal law serializes one component — and it isn’t the trigger pack.
The serial number that makes this object a “firearm” under federal law sits on the
receiver. The trigger group has no serial and is not a regulated firearm on its own. If the trigger
pack were a “lower receiver,” it would be the serialized part. It isn’t.
4. The state applied this exact test and put the MP5 .22 on the excluded side.
Between the May 15 draft and the July 1 final, the Department of Revenue removed the MP5 .22 LR and
the G36 .22 LR (single-receiver HK patterns) while keeping the Walther/Colt M4 .22 (a true
upper/lower). That is the agency reading the “unless” clause the only way it can be read.
5. A manual’s vocabulary is not a legal definition. Owner’s manuals
use familiar words for a lay audience — the MP5 .22 manual’s “lower receiver”
label describes the trigger housing, the same way manuals call a magazine a “clip.” The
statute says separate upper and lower receiver: a construction, not a caption. What the
gun is governs, not what a translated manual calls a piece of it.
6. The “unless” clause was written for a reason, and this isn’t it.
The legislature carved out rimfire guns, then carved back in the AR-pattern .22s — guns that
share a lower receiver with, and can be rebuilt into, centerfire rifles. The MP5 .22 shares no
receiver with anything centerfire; its single receiver is a dedicated rimfire frame that cannot
host a 9mm upper because it has no upper. It is precisely the gun the exclusion was written to
leave alone.
Rimfire-only: yes. Separate upper and lower: no.
By the statute’s own words, that is the end of the analysis.
The Exchange
Four emails in seventy-three minutes.
12:42 PM · The buyer → the compliance manager
After a phone call in which staff said they weren’t sure the gun could be sold, the buyer
— a new member of the store — put his case in writing. He said plainly he’d rather
buy from them than anywhere else, and that he understood it was their license on the line. Then he
laid out three things:
The statute exempts rimfire-only guns without a separate upper and lower, and
the MP5 .22 is a single receiver with a removable trigger pack.
The state’s guidance removed this exact model between draft and final
while keeping the AR-pattern .22 — with links to both documents.
A path to official cover: the guidance isn’t binding, but the state offers
a Statement of Position and declaratory-order process. He offered to help file one so the state
would be on record for this model before any transfer.
He closed: if they still preferred not to sell it, no hard feelings.
1:03 PM · The compliance manager → the buyer
Three sentences. He had already looked into this gun. The owner’s manual
names the trigger group as the “lower receiver.” On that basis, he considers it a
specified semiautomatic firearm.
1:43 PM · The buyer → Umarex USA and HK USA (dealer copied)
The buyer didn’t argue. He went to the source. Copying the compliance manager and forwarding
his determination, he asked the manufacturer three purely factual questions about the product
— explicitly not asking for legal advice:
Is the MP5 .22 LR built with a separate upper and lower receiver, or a single receiver plus a
removable fire-control group?
Is the manual’s “lower receiver” label an official designation of that part as
a firearm receiver, or a descriptive term for the assembly?
Which single component is the serialized firearm under U.S. federal law?
He asked for a short written answer both he and the dealer could rely on.
1:52 PM · The compliance manager → the buyer
Nine minutes later, before any manufacturer could reply:
“Regardless of what HK says, we are still considering it an SSF.”
1:55 PM · The buyer → the compliance manager
He thanked him for his time, said he understood and respected the decision, and signed off.
A fact the manufacturer could supply would not have changed the answer.
That sentence is the whole story. The question “how is this gun built?” has one true
answer, and the people who build it were asked for it. The dealer said in advance that the answer
didn’t matter.
Why This Happened — and Why It Isn’t the Dealer’s Fault
Look at the incentives SB25-003 creates. A dealer who transfers a covered gun to someone without the
card faces criminal liability and their federal license. A dealer who refuses to sell an
uncovered gun faces nothing at all — a lost sale. The guidance list is expressly
“not final agency action,” so it protects no one. The statute’s test turns on a term
of art (“separate upper and lower receiver”) that a marketing manual can casually contradict.
And the process for getting the state to actually commit — a Statement of Position — takes
time, paperwork, and a buyer willing to fight for a plinker.
Put a careful compliance officer inside those incentives and the outcome is almost mechanical. When
“maybe” costs your livelihood and “no” costs nothing, every ambiguous gun
becomes a banned gun. The law doesn’t have to prohibit a firearm to take it off the
shelf. It only has to make a dealer afraid of it.
The rimfire exemption exists on paper.
At the counter, it was overruled by a word in an owner’s manual.
This is the “cumulative burden” the plaintiffs in Del Toro v. Polis are describing to a federal judge —
not one wall, but a stack of fees, cards, courses, vague definitions, and non-binding lists that
together turn a right you have into a purchase you can’t make. Multiply this afternoon across
every counter in the state and you have the law as it actually operates.
For the record · what we can and can’t say
The account above is drawn from a written email exchange on August 25, 2026, reproduced with names,
contact details, and the store’s identity removed. The manufacturer had not responded as of
publication; if it does, we will update this page. We are not saying the dealer broke any law —
it didn’t. Declining a sale is its right. We are saying the law made declining the only safe
answer, and that is the infringement.
Every “no” like this one is evidence.
If you’ve been refused a sale on a gun the law doesn’t cover, or a county that
can’t issue the card, write it down while it’s fresh — date, model, what you were
told. Then put it in front of the people carrying the lawsuit.
Not legal advice · I am not a lawyer · Read the law for yourself
The author of this site is not an attorney and does not practice law. Nothing published
here is legal advice, no part of it is offered as legal advice, and reading it creates no
attorney-client relationship with anyone. This is Second Amendment advocacy and general-interest
commentary written by a private citizen, and it includes opinion.
Read the primary sources yourself. Statutes, ordinances, court orders, and official agency
guidance are linked throughout this site so that you can check every claim against the original. If
anything here conflicts with the actual law, the law controls and this page is simply wrong.
The law changes; this page may not. Whether any particular firearm falls within the statute depends on its physical construction and on how the statute is ultimately interpreted by the courts; the Department of Revenue’s guidance is expressly non-binding and has already been revised once. Legislatures amend statutes, agencies
reissue guidance, courts rule and reverse, and orders are dissolved. Anything here may be out of date
by the time you read it, and no commitment is made to update it.
No warranty of any kind. This material is provided “as is,” without warranty
express or implied as to accuracy, completeness, currency, or fitness for any purpose. Errors,
omissions, and misreadings are possible.
You act at your own risk. To the fullest extent permitted by law, Rearm US LLC, its
members, and the authors of this site accept no liability for any loss, damage, penalty, prosecution,
or other consequence arising from any person’s action or inaction based on anything published
here.
Consult a licensed Colorado attorney before you buy, sell, transfer, carry, build, modify,
or possess any firearm, magazine, or accessory whose legality is in any doubt — and before you
rely on any statute, case, or order described here.
Outside links are not endorsements. We do not control third-party websites or documents and
are not responsible for their content, accuracy, or availability.
This account is one buyer’s experience, not a rule you can rely on. A licensed dealer may lawfully decline any sale for any lawful reason, and a dealer’s judgment about a particular firearm is theirs to make. Nothing here criticizes any dealer’s legal compliance or should be read as advice to attempt any transaction.