A steel tightbore at a sensible price
Most affordable precision barrels are brass. This Big Dragon one is steel, which changes how it behaves in the gun. Steel is stiffer, so the barrel resists flexing and vibrating as the piston slams home, and it is harder wearing over a long life of BBs running through it. Combined with the 6.03mm precision bore, down from the 6.05mm to 6.08mm of a typical stock barrel, you get a tighter air seal behind the BB and a straighter, more repeatable path out of the muzzle. The finish is bright polished inside and out.
Choosing between 229mm and 310mm
Match the barrel to your outer barrel assembly rather than to the overall length of the gun:
- 229mm is the Tokyo Marui reference length for the MP5 family, covering MP5A4, MP5A5, SD5, SD6 and MP5 RAS, and it also suits the AK Beta Spetsnaz.
- 310mm covers mid length carbines. It is the length used for the Krytac LVOA-S, it suits 10.5in to 12in M4 and CQBR style builds, and it is a common choice for shorter modern AKs such as the AK105 and Tokyo Marui Next Gen AK.
Manufacturers follow the Marui lengths closely but not exactly, so measure your existing inner barrel before ordering. If you fall between two sizes, round down. A slightly short barrel works fine, whereas one that is too long will poke past the muzzle or foul the outer barrel assembly.
Steel or brass, which should you buy
Neither is simply better and both are honest choices. Brass is softer, very easy to clean and slightly kinder to BBs, and it is what most barrels in this price bracket use. Steel is more rigid, so it damps vibration better and holds its shape over time, and it stands up to more cleaning cycles. If your build runs a hotter spring, or you shoot enough that a barrel gets cleaned every game day, the extra rigidity and durability of steel is worth having. If you are unsure, either will comfortably out perform the stock barrel it is replacing.
Fitting it and chronographing after
Fitting is a standard inner barrel swap. You pull the barrel and hop assembly out, release the C clip, transfer your bucking across and reassemble with the hop window sitting at the top. No permanent modification is needed and nothing is cut. Because a tighter bore can raise your output a little, chronograph the gun after fitting and adjust hop tension or spring to stay within your site limits. Our guide to UK airsoft FPS limits explains where those caps usually sit, and if you would rather have it done for you our Rochester repair and upgrade workshop can fit, re-shim and chrono the gun.
Get the full benefit
A precision bore is only half the job. The hop rubber does most of the work of putting a BB where you are aiming, so fit a fresh hop rubber and nub alongside it if yours is tired. Tight bores are also less tolerant of poor ammunition, so use good quality seamless airsoft BBs and keep the bore clean with an unjamming rod and a patch. Our BB weight guide covers which weight suits your setup, our guide to which upgrades to do first puts the barrel in context, and you can see the rest of our range of airsoft inner barrels if you need a different length.
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