JK Armament Suppressor: RPX 9K Specs, Setup and Fit
JK Armament suppressors come from southern Idaho, and the RPX 9K is the compact 9mm model, configurable from 3.3 to 7.25 inches.
In This Article
- JK Armament RPX 9K Specs
- What Comes in the Box
- How Long Is the RPX 9K? Setting Length and Weight
- Booster or Direct Thread Mount?
- Which Guns Fit the RPX 9K?
- How to Buy a JK Armament Suppressor
- How Quiet Is the RPX 9K?
- Cleaning, Care and Warranty
- Win the RPX 9K in the Giving Thanks Giveaway
- Suppressor news that matters
Last updated: November 1, 2026 · Originally published October 31, 2026
JK Armament, founded in 2019 in southern Idaho by U.S. Army veteran and former Special Forces Group head armorer Jake Kunsky, has built a reputation for modular, mission-configurable suppressors manufactured in the USA and backed by an unlimited lifetime warranty. The company focuses on lightweight designs that balance durability with real-world versatility across pistols, PCCs, and rifles.
The JK 155 RPX™ 9K is the shorter, booster-ready variant of the RPX platform, optimized specifically for 9mm pistols and pistol-caliber carbines. It ships ready to run with a 1/2-28 piston/booster assembly and a high-flow flash-hiding end cap, while its tool-free modular baffle system lets users adjust length (from roughly 3.3″ to 7.25″) and weight (about 7.5–13.1 oz) for the host and mission. Built with a Grade 5 titanium blast baffle and 7075 billet aluminum baffles in a 1.55″ diameter package, the RPX 9K delivers reliable cycling, multi-caliber flexibility (including select rifle cartridges under rated conditions), and straightforward HUB compatibility, making it a practical choice for shooters who want strong suppression without excess bulk.
Sponsor note. JK Armament is a sponsor of our Giving Thanks giveaway and donated the suppressor this page covers. Legal and safety note. Specs come from JK Armament’s own pages and manual, read in October 2026. Suppressor law varies by state, and this page is general information, not legal advice. No link on this site earns us a commission. Unload the firearm and open the action before you mount or remove any suppressor.
Enter the Giving Thanks giveaway here: fill in your name, email and date of birth below.
Giving Thanks $10,000+ Guns & Gear Giveaway
Here’s the thing about a 9mm suppressor: it usually has to live on two guns, a pistol that wants it short and light and a carbine that does not care how long it is. The RPX 9K is JK’s answer. And before anything threads onto a muzzle, the gun is unloaded with the action open (JK’s manual puts that in its opening warnings, ahead of the installation steps).
JK Armament RPX 9K at a Glance
- Price and colors: $795.00 on JK’s own site, in Black or FDE.
- Size: 3.3 to 7.25 inches long with the mount, 1.55 inches in diameter.
- Weight: 7.5 to 13.1 ounces with the mount, depending on how many baffles you run.
- Rated for: 9×19mm, .38 Special, .357 Magnum and all smaller pistol cartridges, full-auto, with no minimum barrel length.
- Mount: ships with a 1/2×28 piston and booster installed, plus a high-flow flash-hiding end cap.
JK Armament RPX 9K Specs
The JK Armament 155 RPX™ 9K is a compact, mission-configurable 9mm suppressor measuring 1.55 inches in diameter, with an adjustable overall length of 3.3 to 7.25 inches (or 2.8 to 7 inches without the mount) and a weight range of 7.5 to 13.1 ounces depending on configuration (2.8 to 8.5 ounces without the mount). It is constructed from a Ti-6Al-4V (Grade 5) titanium blast baffle paired with modular 7075 billet aluminum baffles, finished in Type 3 hard anodize and Cerakote, and offered in Black or FDE. The suppressor ships with a 1/2-28 piston/booster assembly, a high-flow flash-hiding end cap, a short tube, one PRO pistol baffle, and five LT pistol baffles; it is full-auto rated for 9mm and smaller pistol cartridges (plus 300 Blackout) with no minimum barrel length.
| Spec | RPX 9K | What it means for you |
|---|---|---|
| Price | $795.00 (maker price) | JK’s own listed price; dealer prices vary |
| Length | 3.3 to 7.25 in. with mount; 2.8 to 7 in. without | You set it by adding or removing baffles |
| Diameter | 1.55 in. | The “155” in the JK 155 series name |
| Weight | 7.5 to 13.1 oz with mount; 2.8 to 8.5 oz without | The mount accounts for 4.6 to 4.7 oz of it |
| Materials and finish | Ti-6Al-4V (Grade 5) titanium and 7075 billet aluminum; Type 3 hard anodize and Cerakote | Black or FDE (Flat Dark Earth) |
| Caliber rating | 9×19mm, .38 Special, .357 Magnum and all smaller pistol cartridges; full-auto; no minimum barrel length | Built for 9mm pistols and pistol-caliber carbines |
| Mount in the box | 1/2×28 piston and booster housing, installed | Threads onto a 1/2×28 barrel; JK sells other mounts separately |
| Warranty | “Unlimited, unconditional, lifetime warranty” | Terms are in JK’s manual (see below) |
Specs, price and finishes are from JK Armament’s RPX 9K product page, read October 27, 2026; the mount’s share of the weight is our arithmetic from JK’s two weight ranges (7.5 minus 2.8 ounces short, 13.1 minus 8.5 ounces long). Prices change, so check the maker before you buy.
What Comes in the Box
JK’s “Includes” list tells you how the thing is built:
- (1) JK 155 booster housing and 1/2×28 piston
- (1) JK 155 LT 2.5-inch tube
- (1) JK 155 PRO pistol baffle
- (5) JK 155 LT pistol baffles
- (1) JK 155 LT high-flow flash hider end cap
So the full-length RPX 9K is six baffles between a booster and an end cap. JK describes those baffles as its “most advanced rifle-pistol baffle geometry,” and says the modular design lets you “dial in the length and weight that best suits your firearm and mission.” Remember, that is the maker talking, and JK publishes no decibel figure for this model.
How Long Is the RPX 9K? Setting Length and Weight
With the mount on, JK’s numbers put the RPX 9K at 3.3 to 7.25 inches, a spread of 3.95 inches, and 7.5 to 13.1 ounces, a spread of 5.6 ounces. The body alone runs 2.8 to 7 inches and 2.8 to 8.5 ounces.
Changing length is owner work, not gunsmith work. JK’s manual says to unthread each component (a JK 155 wrench helps), hand-tighten on reassembly, never exceed 10 foot-pounds if you torque it, and add one drop of blue 242 thread locker only if you want it. Thread locker may mean heating it before it comes apart.
Booster or Direct Thread Mount?
The RPX 9K ships with what JK calls a “1/2-28 piston / booster setup right out of the box,” and JK says it is “optimized for reliable function on boosted 9mm platforms.” JK’s piston mount page explains the job in one sentence: “By isolating the suppressor from the moving barrel, the JK HUB Piston Mount maintains reliable operation of short recoil-operated, semi-automatic pistols.” JK says that covers “nearly every other modern, centerfire pistol.” In plain English, those barrels move when they cycle, and the booster keeps the suppressor’s weight out of the way.
JK’s manual makes the same point backward: its lighter JK 105 CCX “does not need a booster” on tilt-barrel pistols “because of its lightweight construction.” The RPX 9K is not that suppressor, so the booster stays on for pistol work.
What about a carbine? Every JK 155 mount threads into the base of the tube on the 1.375×24 thread that JK calls the HUB standard, and JK sells a 155HD Direct Thread Mount in 1/2×28, 5/8×24, 1/2×36, 11/16×24 and .578×28. JK describes the booster’s whole job as isolating the suppressor from a moving barrel. A pistol-caliber carbine with a fixed barrel has no moving barrel, so on a carbine the booster has nothing to do. The direct thread mount is also lighter: JK lists it at 2.1 ounces, against 4.6 to 4.7 ounces for the booster mount by JK’s own weight ranges, which saves about 2.5 ounces on the muzzle. Match the mount to your carbine’s muzzle thread; JK makes it in the five threads listed above.
Which Guns Fit the RPX 9K?
JK calls the RPX 9K “perfect for pistol caliber carbines and 9mm handguns” and an “excellent choice for 9mm pistols, PCCs, and lightweight rigs.” The rating line backs that up: 9×19mm, .38 Special, .357 Magnum and all smaller pistol cartridges, full-auto, with no minimum barrel length.
Three things decide whether it goes on YOUR gun:
- Thread pitch. The piston in the box is 1/2×28. A barrel threaded to another pitch needs a different piston or mount from JK.
- Caliber. Tuned for 9mm
- Fit at the shoulder. JK’s manual says the mount “must be fully shouldered on the barrel,” with no visible gap, and to never use a crush washer when mounting a suppressor.
JK also says to check that the suppressor is still tight after 30 rounds, and to use heat-resistant gloves taking it off.
How to Buy a JK Armament Suppressor
Buying a JK Armament suppressor starts on jkarmament.com: buy there, name your local dealer at checkout, and the suppressor ships to that dealer. JK’s buying box still describes the older eForm 4 route and quotes 27 days for an individual and 123 days for a trust. Since October 9, 2026, ATF is not enforcing that approval step, so the dealer can transfer it on a Form 4473 with a background check, as the next section explains. If you file a Form 4 anyway, ATF’s own processing-times page lists 6 days for an individual eForm 4 and 20 days for a trust (averages for applications finalized in August 2026), and our ATF wait times tracker follows those numbers month to month.
The federal rules underneath that box changed in 2026, so here is where things stand:
- The tax is $0. Since January 1, 2026, federal law sets the transfer tax at “$0” for everything but machine guns and destructive devices, which still carry $200.
- ATF stopped enforcing the paperwork, for now. On October 9, 2026, ATF said it “will not enforce the requirements for individuals to apply and receive ATF approval before making or transferring” suppressors, short-barreled rifles, short-barreled shotguns and certain other weapons, and “will not enforce the NFA’s registration, tax-stamp or related requirements” for them. It applied that to everyone, not only the parties to the Texas court’s injunction. A suppressor is still an NFA firearm in the statute; this is an enforcement policy.
- The dealer still runs a background check. ATF says licensees “must fill out an ATF Form 4473” and run NICS, and with limited exceptions sell only to residents of their own state.
- State law still governs. ATF says its guidance “does not supersede state and local laws that restrict NFA firearms,” and it still processes Form 4s for anyone who files one. Civilian suppressor ownership is banned in California, Delaware, Hawaii, Illinois, Massachusetts, New Jersey, New York, Rhode Island and Washington, D.C. (which squares with JK’s “42 states permit suppressor ownership”). Other states tie their law to federal registration, so buyers there should expect a Form 4 anyway.
ATF says enforcement could return with a new tax, a dissolved or overturned injunction, or rescinded guidelines. Our guide to buying a suppressor after October 9 walks the checkout step by step, and the suppressor laws by state page shows which group your state falls in.
How Quiet Is the RPX 9K?
As a shorter “K” configuration of the RPX platform, the JK Armament 155 RPX 9K prioritizes a compact, pistol- and PCC-friendly package over maximum sound reduction, with overall quietness highly dependent on baffle count, ammunition (subsonic loads perform best), and host firearm. Official and early user feedback on the related full-size RPX 9mm is positive: one owner reported that “subsonic 9mm loads sound like a pellet gun,” while another noted that “all Subsonic rounds have been under 92 db. Very Quiet!” JK Armament has described the 9K itself as a strong choice for a fun range toy that delivers solid sound reduction, enough to keep ears from ringing, though it is not hearing-safe in shorter setups. Running the full baffle stack increases suppression at the cost of added length and weight, while the high-flow end cap helps manage pressure and tone across configurations.
Cleaning, Care and Warranty
Cleaning a JK Armament suppressor is spelled out in JK’s manual, which JK says covers all of its suppressors: an ammonia-free CLP and a nylon brush, with carbon kept off the threads and the faces of every component. The manual warns that lead and other toxic materials collect inside, so take precautions and dispose of the gunk properly. A light coat of CLP goes on the threads before reassembly.
JK’s warranty page puts it simply: “We guarantee our products for life,” and the product page calls it an “unlimited, unconditional, lifetime warranty.” The 2022 manual is narrower on paper: it covers “defects in material and workmanship,” limited to repair or replacement, and excludes things like misuse, improper mounting and reloaded ammunition. To start a claim, JK’s FAQ says to submit its web form. The manual also asks for a copy of your Form 3 or Form 4, so if you took delivery on a Form 4473 alone, say so in the form.
Win the RPX 9K in the Giving Thanks Giveaway
The JK Armament RPX 9K in black is one of 15 prizes in Brand Avalanche Media’s Giving Thanks $10,000+ Guns & Gear Giveaway, and one winner takes all 15 prizes, worth $10,000+ in total. It is free to enter and runs November 1–30, 2026, ending at 11:59 p.m. Central on November 30, open to legal U.S. residents 21 and older, except in New York and Florida. No purchase necessary. Firearm prizes ship to the winner’s local FFL. The suppressor transfers through a dealer licensed for NFA items after any required ATF approval, and if the winner lives where suppressors are banned, the winner still gets the other prizes and the suppressor goes to an alternate winner (the official rules on the entry form govern). The same prize list includes an OA Defense 2311 Compact Standard Elite pistol package, a Magnum Research BFR revolver in .360 Buckhammer and 1,000 rounds of Nosler 9mm 115-grain ASP, which is a lot of 9mm to put through a new suppressor (Popular Ammo’s 9mm self-defense ammo guide covers 9mm hollow points like it). Read the rules and the full prize list on the Giving Thanks giveaway page at Guns and Gadgets Daily.
A .22 rimfire leads at 35%. 300 Blackout and the deer rifle tie for second at 23% each.
Frequently Asked Questions
Is JK Armament a good suppressor brand?
We do not rank suppressors we have not tested side by side. By JK’s own account, a JK Armament suppressor comes from a company founded in 2019 by Jake Kunsky, a U.S. Army veteran who served as a Special Forces Group head armorer, in four product series (JK 105, 155, 172 and 195), with a lifetime warranty against defects in material and workmanship.
How much is the JK Armament RPX 9K?
JK lists it at $795.00 in Black or FDE. Dealer prices vary, and a second mount, such as JK’s 155HD Direct Thread Mount at $105.00, is extra.
Where is JK Armament made?
Idaho. JK calls its products American-made, and the tube in its own RPX 9K product photo is marked “JK Armament, Hammett, Idaho.” Its site footer reads “A Product of UES.”
Can you put the RPX 9K on a 9mm pistol?
Yes, if the barrel is threaded 1/2×28 and the mount seats fully against the shoulder. That is what JK built it for, with the booster installed and no minimum barrel length.
Is the suppressor tax stamp still $200?
No. The federal transfer tax on a suppressor has been $0 since January 1, 2026, and since October 9, 2026 ATF has said it will not enforce the approval, registration or tax-stamp requirements for suppressors. The dealer’s Form 4473 and background check remain, and so does every state ban.
The RPX 9K is a JK Armament suppressor that does not make you pick between the range and the holster: run all six baffles on the carbine, pull a few for the pistol, and the booster comes along for both. Check your thread pitch and your state’s row first, and you will only have to buy it once.
Sources: JK Armament, “RPX™ 9K”; JK Armament, “About Us”; JK Armament, “Warranty and Manuals”; JK Armament, “FAQ”; JK Armament, “JK Armament 195, 155, & 105 Series” manual; JK Armament, “JK 155 HUB Piston Mounts Black”; JK Armament, “JK 155HD Direct Thread Mount”; 26 U.S.C. 5811, transfer tax (Cornell LII mirror); ATF, “ATF Issues Guidance on National Firearms Act Transfers” (October 9, 2026); ATF, “Update to NFA Transfer Guidance”; ATF, “Current Processing Times”; Murphy et al., International Journal of Audiology, “The reduction of gunshot noise and auditory risk through the use of firearm suppressors and low-velocity ammunition” (2018); OSHA, 29 CFR 1910.95, occupational noise exposure.
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