In October of 2024 I put together a speed build on my FX Impact M4 with a Saber Tactical buttstock, an Element Immersive 5x, an Accu-Tac WB-4 bipod, the FX Quick Set Trigger and a DonnyFL QD Ryu on the front. That rifle was about being light, quick and handy, and the Ryu was a big part of why it worked, because it gave the gun real suppression without adding length or weight that would undo the whole point of the build. The DonnyFL RYU has become my favorite small moderator for exactly that kind of rifle, and in this Field Notes post I want to walk through how it is built and how to get the most out of it.
The DonnyFL RYU, a 1.22 x 5.25 inch modular moderator with an indexed quick detach.
Quick Summary
- The moderator: DonnyFL RYU, 1.22 inches (30.48mm) in diameter and 5.25 inches long, with an indexed quick detach.
- Construction: 6061 T6 sections with a 7075 aluminum QD housing and adapter, and a 1/2 x 20 female thread adapter included.
- Modular: RYU Spare Baffles let you lengthen it, with no more than 2 extra before going up a caliber.
- Extra rifles: a QD Barrel Adapter in 1/2 x 20 or M14x1.25 lets one RYU serve several guns.
- Maintenance: the Ryu Refresh Kit includes 5 O-rings and a washer.
From KOI to RYU
In Japanese mythology the koi carp symbolizes samurai warriors braving upstream battles to the top of waterfalls, and those that make it are transformed into dragons. RYU is Japanese for dragon, and the name fits, because the RYU is the robust, evolved version of our slim KOI. It keeps a diameter of 1.2 inches, or 30.48mm, and it adds a quick detach system and a modular body.
The individual sections are crafted from 6061 T6 aluminum, while the main QD housing and adapter are made from 7075 aluminum. Every RYU comes with a standard 1/2 x 20 female thread adapter for barrel or shroud attachment.
The RYU is the evolved, modular, quick detach version of the KOI.
How the Indexed QD Works
The RYU uses an indexed locking system, which means it locks onto the adapter in the same position every time. That consistency is what gives you no point of impact change after detaching and reattaching, so you can pull the moderator for storage or transport and put it back on without re-zeroing.
This version uses the original spring set QD, which has served a lot of shooters very well. The practical benefit on a small rifle is that you can take the moderator off to fit the gun in a case or a pack, then put it back on at the field with confidence that it will shoot where it did before.
Sizing
If you are connecting directly to a threaded barrel, purchase the same size as your airgun. If you are connecting to a shrouded barrel or using an adapter, go one size up.
Adding Spare Baffles
The RYU is modular, so you can lengthen it to meet your specific dampening needs. The DonnyFL Spare Baffles for the RYU let you customize the size or replace individual sections, and our recommendation is not to add more than 2 extra baffles on top of the factory unit. If you plan to go further than that, consider going one caliber size up for more bore clearance.
That flexibility is what makes the RYU so useful on shorty builds. You can run it in its compact factory length on a light hunting rifle, and add a section or two when you move it to a rifle that is running more power.
RYU spare baffles let you tune length to the rifle.
One RYU, Several Rifles
Because the RYU is quick detach, a second QD Barrel Adapter on another rifle lets the same moderator move between guns. The adapter is 7075 aluminum, anodized, and available in 1/2 x 20 or M14x1.25, and it includes a set screw and wrench. Note that this is only the barrel adapter, and the moderator rear cap is not included.
Before you move the RYU between rifles, check that the caliber sizing still makes sense for both guns, because a RYU sized for a .22 should not be moved to a .25 without stepping up.
Keeping the RYU Fresh
O-rings are what keep the sections sealed and the lock-up tight, and over time they wear. The Ryu Refresh Kit includes 5 replacement O-rings and 1 washer and fits all Ryu models, which makes it an inexpensive way to bring an older unit back to like new.
RYU Quick Checklist
Same size as the gun on a threaded barrel, one size up on a shroud.
No more than 2 extra baffles without going up a caliber.
Use a QD barrel adapter on each rifle you want to share the RYU with.
Refresh the O-rings when the lock-up starts to feel loose.
Frequently Asked Questions
How big is the DonnyFL RYU?
The RYU is 1.22 inches, or 30.48mm, in diameter and 5.25 inches long in its factory configuration.
Does the RYU change point of impact when I remove it?
The RYU uses an indexed locking system that locks on in the same position every time, so there should be no point of impact change after detaching and reattaching.
Does the RYU come with an adapter?
Yes, it comes with a 1/2 x 20 female thread adapter for barrel or shroud attachment. Some rifles need an additional DonnyFL adapter to reach 1/2 x 20.
Can I add baffles to the RYU?
Yes, RYU Spare Baffles let you lengthen it, but we recommend no more than 2 extra baffles on top of the factory unit, and going one caliber size up if you do.
Can I use one RYU on several rifles?
Yes, Install a DonnyFL QD Barrel Adapter, available in 1/2 x 20 or M14x1.25, on each rifle and move the RYU between them.
What is in the Ryu Refresh Kit?
The Ryu Refresh Kit M148 includes 5 replacement O-rings and 1 washer and fits all Ryu models.
Final Thoughts
The RYU is the moderator I reach for when a rifle is meant to be small, light and quick, and its quick detach design means it never gets in the way when it is time to pack up. Size it correctly, add baffles thoughtfully, and keep a refresh kit on hand, and it will serve a whole rack of shorty builds.
