Umbrella Prometheus 6.03 EG inner barrel with R-hop

Type: Assembly
Lapping Service?
Low stock

~3 Week Build Time

A truly timeless, tried and true setup.

Be aware, shots will be erratic/inaccurate for the first 5,000 rounds put through, it takes a little time for the patch to break in and conform to the shape of a BB. Once you play a couple of games you should be shooting extremely accurate! 

Prometheus 6.03 EG inner barrel with installed R-Hop modification. Available with a pre-assembled drop in kit for compatible TM spec M4 type AEG/HPA Airsoft guns.

The perfect upgrade for any gun, to increase accuracy, range and consistency of each shot fired. Out range anyone else on the field with incredible range and accuracy despite FPS.

Our handmade R-Hop has been an integral modification we perform for all our builds as users can experience 30% increased effective range over non R-Hopped barrels.

Purchase in a complete drop in assembly configuration for a true plug and play upgrade process if your build uses a Tokyo Marui spec M4 style hop up unit.

Please note that there is a little slit in the patch near the end of the barrel, that slit is intended to help vent air pressure on high RPS builds to keep everything more consistent. This does not effect performance negatively in any way on any build no matter the RPS or sector gear, strictly meant to improve performance on high RPS.  


  • Inner diameter: 6.03 millimeter 
  • Polished finish, Mirrored Finish if Lapped
  • Precision, hand fitted R-Hop patch
  • R-Hopped glued into hop window 
  • Umbrella Armory specific R-Hop 2.0 patch design and material
  • Requires flat bucking and M-Nubbed / R-Hopped style hop up arm for use (included/assembled with full set)
  • Use .28 gram BBs or heavier to see optimal long range advantage over non R-Hopped comparisons


  • SUS 304 stainless steel inner barrel
  • Rubber R-Hop patch



What is it? Its a grinding method to microscopically remove material from the surface of the bore. Using extremely fine diamond compounds, we can remove material from the inside of the barrel that is uniform and consistent throughout the bore. Leaving a mirror-like finish that's very time consuming to achieve on a steel barrel.

As a result, the following happens.

  • ~2% increase in FPS
  • Increased shot to shot FPS consistency
  • Increased accuracy downrange
  • Easier barrel cleaning/less stubborn residue buildup

Below is an example of a Prometheus Barrel 6.03mm, pits, and bore marks can be seen within the barrel. With lab instruments we've measured this low/high spread as 5 microns. These microscopic holes tend to catch BB residues, and increase the internal friction of the barrel slowing down the BB.

Below is that same barrel with our lapping process done to it. We're able to reduce the internal bore surface roughness to below 0.5 micron. Resulting in a mesmerizing mirrored effect on the inside.

Customer Reviews

Based on 9 reviews
Bo-Rickard Jepson
Best Upgraded!

Made my MTW shoot perfect!

Mike B
Amazing barrel

I have 3 Rhop barrels they are the best barrels out there. The accuracy is crazy on these barrels. The grouping is amazing.

Thank you so much for your support, and having 3 barrels from us!

Giles Madruga
Very good barrel set up

Shot better then I thought it would 100% recommend

Best barrel

Best barrel I've put in a replica yet. Bought 2 different lengths, both lapped and R hopped. One went into my Wolverine forged tactical and the other for my Kythera build. Both shoot laser beams now. Plan on getting more for my other 3 builds.

Kevin Johnson
Best upgrade I’ve done

This has been the best upgrade I’ve done. I had it paired with a prowin HopUp but I found that a maxpro me HopUp gave a beater seal and better adjustability. This thing shoots laser beams and outranges most players