SCW stands for "Shibuya Custom Works" and refers to the shop they have in Shibuya, Tokyo. Originally SCW only referred to the limited batch of "custom guns" that came from the engineers at the shop. However in 2003 they introduced the "SCW system" which they have steadily improved and implemented. When you look for a WA gun, be careful to distinguish between the "Shibuya Custom Works" guns that are limited in production and the "SCW system" because they are not the same. I must admit i'm not 100% sure what magna tech is. Primarily it's the budget line of guns from WA (most guns branded Magna Tech cost 50% of the ordinary WA guns) that has some lighter plastic and less expensive finish. The technology, however, is still the same. the first gun with SCW system was sold in april 2004.

SCW "I": four major points were redesigned. (1) a new hopup system that didn't require you to remove the slide in order to adjust the hopup (the hopup is adjusted with a 1mm allen key in the chamber) (2) the gas system was redesigned to let out the same amount of gas no matter what the pressure was. WA used to have big problems with gas being let out in uneven portions, resulting in the inability to empty a full magazine with one gas charge on some guns. (3) the redesigned gas cylinder provides a larger quantity of gas for the blowback and also lowers the amount of gas leakage (4) redesigned strikepin and hammer which gives smoother action.

SCW2: Redesigned magazine for the 1911 with doublestack of BBs even on the "single stack replica" magazines. The WA 1911 magazines used to hold 12-15BBs, post-SCW2 mags hold 19-23BBs (depending on the size of the gun). SCW2 also introduced an improved strikepin mechanism and reinforced hammer-, strike- and fingerspring.

SCW3: (1) Completely redesigned hopup which is no longer variable. Very precise and very effective, however. WA recommends the use of 0.25g BBs with SCW3 guns. (2) The blurb was "Gas Control System II - makes the gasflow mimic that of a real gun". I still to this date have no idea what that implies. (3) The hammer was once again redesigned, to mimic the properties of a real hammer more closely. (4) A new sear and rear disconnector was implemented. This gives the SCW3 guns a smoother cycle than earlier WA guns.

These are the differences I can think of from the top of my head. Remember that SCW is a proprietary technology that WA keeps improving. The parts are different from different versions, where as you cannot buy spare parts branded SCW2 and put them in other guns but with SCW2. The difference between shooting a pre-SCW and SCW guns are rather big. the blowback is much heavier and smoother in SCW guns, and personally i think WA still has the best overall feeling of quality in their guns. it should however be noted that the WA guns performance wise drag behind Tokyo Marui's recent line of GBBs starting with the Desert Eagle and it's following guns. the main reason for this is that WA's hopup system always has been a major issue. It was remedied with the SCW3 introduction but then you have little choice but to use 0.25g BBs which in some cases might not be preferable.