Umbrella Armory R-Hop

Prometheus 6.03mm R-Hop barrel FAQ:

Will this work in my x?

If selecting the full set; your assembly should work in most M4 style AEG receivers that are compatible with the standard Tokyo Marui M4 single piece Hop up chamber design.
Models that use two piece hop up units are not compatible with the full set.
ICS models are not compatible with the full set.
KWA models are not compatible with the full set.
Wolverine MTWs are not compatible with the full set.

This is not a conclusive list as there are thousands of options on the market. If this assembly is not compatible, email our customer support to receive instructions on getting a full refund/exchange.

Otherwise, you may purchase the barrel by itself as well as our flat hopped bucking and one of our custom made flat arms to easily convert your hop up unit to be compatible with our R-hop barrel.

How do I install?

For complete R-Hop Assembly Packages:

We will send rubber O-Rings with all our barrel assemblies to replace spring spacers most Airsoft guns use. These O-Rings provide much better support and add increased accuracy, air seal, and overall alignment. It varies on how many O-Rings are needed as it is different across different guns, but for reference: stock Krytacs and VFCs use 3 O-Rings while other brands may need more or less. To find out how many you need, make sure to remove any barrel assembly springs from your gun and try installing as many O-Rings as you can while also being able to put your receiver together. It should not have to require too much strength however what we are looking for is after the barrel is installed and gun is reassembled, you should not be able to have any play/movement with the hop up unit when trying to move it inside your magazine well. After successful installation, there is a break in period of roughly 5000 rounds so you may experience some inaccuracy issues.

For further instructions or support please visit:

For standalone R-Hop Barrels:

We highly suggest that with our R-Hop barrels, users use a flat hop bucking and M-Nub modified hop up unit (or Maxx unit). You can find support online for these items, or modifying your current bucking and hop up unit. We offer flat hopped Madbull blue buckings and different hop up arms that should make our R-Hop barrels compatible with other AEG hop up units.

Is there a break-in period?

We advise shooting 5000 as when you should notice optimal results.

Is there any special cleaning instructions?

Please clean your barrel with an unjamming rod and a dry piece of microfiber cloth after every 3000 rounds or so. Absolutely NO silicone oil, grease, water, liquids of any kind. Also no need to disassemble your hop up unit or remove the inner barrel from your hop up unit.

If you notice any issues, please email us so we can advise before you disassemble the barrel assembly.

What weight BB's should I use?

Most guns will need at least .28g BBs before you start seeing the R-Hop advantage take affect.

AEGs that shoot between 350FPS - 410FPS (with .2g BBs) will see the best results with .32g BBs. Using heavier weights will always be the better choice with R-Hop barrel assemblies. With our complete sets you can be able to run as low as .2g BBs with your gun but you may need to use barely any hop up engagement (turned down).

We advise using high quality Bio-friendly BBs to be environmentally conscious. Experiment with different weight BBs while you break in your barrel to find a weight that is perfect for your set up.