So, I'm seeing a lot of threads on subjects like: "what 750mm barrel will give me the most accuracy." and so forth. The real sad part to these questions is, that typically the person asking is putting this brand new $60 plus barrel into a totally stock hop up assembly. This is not the way to improve your accuracy or range. The first and very first thing a person should be doing before turning to the barrel, is fine tuning the hop-up. Only after the hop is tuned should you even consider turning to the inner barrel. If someone is unhappy with their AEGs accuracy, my advice is always to tune the hop-up, use the gun for a while, if you are unhappy with the performance still, then start turning your attention to the inner barrel or other items. So this guide is being written to serve as a starting point for those wanting to increase their accuracy. Step 1: organize your workspace. Before starting on any project, always start with a neat, clean, organized, workspace. Place down a towel to keep the small parts from rolling around. Like so: Step 2: organize your tools. You will need: A naked utility knife blade. A small sheet of aluminum foil Superglue A dremel with cone grinder attachment Dental floss Teflon tape Permatex anaerobic gasket maker. Lube of some kind A solid nub. (SCS, hnub, or even a piece of wire.) A standard squishy nub Step 3: Prepare the Bucking Now, why exactly are we messing with the bucking? Simple, consistency and shape. There is one thing on the inside of these buckings that will, overtime, lead to a inconsistent hop up. A little mound of rubber. To get to this thing, you have to turn the bucking inside out. Now, most of the time, that's easier said than done. Especially with the softer buckings that will tear if you aren't careful. The easiest way to do this is to use your inner barrel and unroll it. It doesn't matter how you do it, just flip it inside out, unharmed. See the little mound now? We need to get rid of this thing. There are a number of ways, I use a dremel, because patience is not one of my virtues. But however you do it, be careful and sand it down out of existence. It should look like so: Well, we are left with a uneven surface that's been roughed up by our removal process. We need a nice clean surface to make contact with the BB. We can achieve this by removing the locking line, much the same way that we removed the mound. Very carefully. It should look like so: BEFORE AFTER Next we need to cut off about 5mm or more off the end of the bucking. We do this because when we go to seal it, the added material of floss and tape will stretch out the bucking, and make it impossible to get the c-clamp on. Use your naked blade, and chop it like so: Now, use your blade and slice a small V at the end of the bucking, pointing at the clean area we want the BB to contact. This is so, when we turn the bucking right side out, you can tell which side is up. Turn the bucking slightly right side out, except for the last 1/4 of it. Like so: Your bucking is now tuned and ready for install.