Just about every KWA/KSC gun I've owned has, at one point or another, swelled the bucking with silicone oil. It's a nice, lightweight oil that plays nice with just about every part in a gun except the buckings they use. The problem is that the swelling creates very bad performance and doesn't fit in the gun. for example, the dial adjuster on GBB pistols will pull a swelled bucking with it, while a new bucking will stay in place as the part rotates around it. While new ones can be bought for $3.50-$5, it was always a waste to have to throw out an otherwise good bucking just because it got oil on it. I found out that acetone breaks down super glue and wouldn't end up harming silicone RHop patches (At least after a soak or two), so I could glue an entire patch in, messy or not, shave and fit the outside, then drop the barrel in acetone to remove the glue. This had the side effect of also swelling the patch, but after airing out it would return to normal and I'd have a perfect fitting patch that could be tacked back in place. Unfortunately, acetone doesn't really remove silicone oil, but a bit of googling says that xylene will, but it'll cause rubber to swell. Had some old swollen buckings and dropped one in a little jar. It swelled, no surprise, but after drying it off and letting it air dry until I could not smell any fumes leaving it, the patch had shrink back to just about new! So if anyone wants to confirm this, let me know! But I've tried it on a couple other buckings and so far have had similar results.