Airsoftpedia Hop-up and accuracy
Inner barrels and hop-up buckings for gas pistols (GBB): lengths and choices
A new inner barrel and a better hop-up bucking are the two upgrades that make the biggest difference to a gas pistol. But a barrel has to be the right length to fit your model, and the bucking has to match the power of your gun. Here is the overview. The guide also applies to CO2 blowback pistols, which use the same barrels and hop-up as the gas versions.
1. Find the right barrel length
The inner barrel must be the same length as the original barrel in your model. If it is too short, the BB is not guided all the way out. If it is too long, you cannot assemble the pistol. Always measure your old barrel if you are in doubt.
The table shows the typical original lengths. Manufacturers sometimes differ by a millimetre or two, so a 112.5 mm barrel and a 113 mm barrel fit the same models.
| Length | Typically fits |
|---|---|
| 74 mm | Tokyo Marui Detonics .45 |
| 85–86 mm | VFC/Umarex Glock 19 and 19X and WE G19 |
| 90 mm | Tokyo Marui M&P9 |
| 95 mm | Tokyo Marui Hi-Capa 4.3 |
| 97 mm | Tokyo Marui Glock 17, Glock 18C and P226, and WE G17 and G18 |
| 100–101 mm | Tokyo Marui XDM-40 and HK45 (100 mm), FN 5-7 (101 mm) |
| 106 mm | Tokyo Marui M92F series |
| 112.5–113 mm | Hi-Capa 5.1, M1911 (Government, MEU, M45A1) and KJ Works Shadow 2 |
| 115 mm | Tokyo Marui M9A1 |
| 129 mm | Action Army AAP-01 (original length) |
| 133–150 mm | Tokyo Marui MK23 (depends on manufacturer) |
| 136 mm | Tokyo Marui Desert Eagle |
| 180–200 mm | AAP-01 with extended outer barrel or barrel extension |
| 410 mm | WE GBB M4 and HK416 |
The WE G series follows the Glock models: a WE G17 uses the same barrel length as a Glock 17, a WE G19 the same as a Glock 19, and so on.
Length is not the only thing that has to fit. The barrel also has to fit the hop-up chamber. A barrel for a Tokyo Marui Glock will not necessarily fit a VFC Glock, even though the length is almost the same. So always check which model and which brand the barrel is made for. Some barrels are sold as a set with their own hop-up chamber, and then they only fit the model the set is made for.
What do 6.01, 6.02 and 6.03 mm mean?
The number is the barrel's internal diameter. The closer the number is to 6.00 mm, the less air escapes past the BB. That gives more consistent shots, but the barrel has to be kept clean. A 6.01–6.03 mm precision barrel is a clear improvement over most original barrels.
2. Choose the right hop-up bucking
The hop-up bucking puts backspin on the BB so it stays in the air longer. The hardness rating tells you how hard the bucking is. The higher the number, the harder the bucking. A powerful pistol needs a harder bucking, otherwise the BB just pushes it out of the way and gets too little spin.
Maple Leaf recommends this split:
| Hardness | Maple Leaf colour | Suits |
|---|---|---|
| 50° | Green | Below 110 m/s (approx. 1.2 J) |
| 60° | Yellow | 90–120 m/s (0.8–1.5 J) |
| 70° | Blue | 110–140 m/s (1.2–2 J) |
| 80° | Red | Above 140 m/s (above 1.8 J) |
Most gas pistols shoot in the range where 60° or 70° suits. If in doubt, start with 60° for an ordinary gas pistol and 70° for a powerful pistol or a GBB rifle.
Cold and silicone
Rubber gets stiffer in the cold. Silicone hop-up buckings handle cold better and warm up faster. If you play a lot in winter, silicone is a good choice. Many players also choose a slightly softer bucking in winter, because gas pistols shoot weaker when the gas is cold.
The different types of bucking
- Maple Leaf Decepticon: Has a triangular contact surface intended to give better accuracy and range. It fits Tokyo Marui, WE and KJ Works gas pistols and requires an open hop-up window like the Tokyo Marui's.
- Maple Leaf Autobot: Triangular with a W-shaped end and a tight seal intended to reduce power loss. Made for WE, Tokyo Marui and KJ Works.
- Maple Leaf MR: Has a flat, R-hop-style contact surface intended to give maximum range. It is made for slightly heavier BBs (0.25–0.32 g) and fits Tokyo Marui and WE.
For the Decepticon and MR, Maple Leaf recommends a curved or flat hop-up arm, e.g. the Maple Leaf I-Key, instead of the round standard arm.
3. Which BB weight?
A gas pistol with original parts typically shoots best with 0.20–0.25 g BBs. If you have switched to a bucking like the Maple Leaf MR, you can go up in weight. Experiment, and adjust the hop-up every time you change BB weight.
Find the parts
You will find all our barrels for gas and CO2 pistols under Inner barrels for gas & CO2, and hop-up buckings and chambers under Hop-up & hop-up buckings for gas & CO2. Not sure what fits your pistol? Get in touch – we are happy to help.
