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Making a Spring Compressor

spring compressor

Before you can do serious tuning or repair work on a spring airgun, the first tool you need is a spring compressor. You can’t buy one- but you can make one very easily. I’ve seen many plans in airgun magazines over the years, and they’re all pretty similar, as they all do the same job: Hold a barreled action steady while releasing or compressing the mainspring. Where they differ is in the details that each gunsmith adds to their version.

screw clamp

Mine is massively overbuilt- the base is heavy enough and large enough to be self supporting, and one of these days I’m going to build legs for it. Until then it just gets dropped on whatever workbench is handy when I need it. As you can see, the bulk of it consists of a pipe clamp attached to a wooden base. At the free end, the pipe is screw to a flange that in turn is screwed to a vertical surface. The other end sits on a spacer, with a screw passing through the pipe and the spacer into the base. Along the pipe are a series of adjustible clamps that hold the gun steady as the spring is released or compressed.receiver clamp

At the fixed end of the pipe clamp there’s a sliding, locking piece that serves as a fixed point in clamping. At the other end is a screw clamp that attached to the free end of the pipe. Adjacent to both is a piece of wood that is bored to slide along the pipe and act as padding between the metal jaws of the clamp and the gun. Some airgunsmiths like to add extra padding in the way of cork or felt to these pads, but if you make your clamp of of softwood, as I did, there’s no need.

To release a spring, the gun is first disassembled and clamped in the fixture with the clamp run in as far as it will go- this provides enough room to extend the spring after it is released. Then, any screws or retaining pins holding the end block in are removed, and the clamp is backed out, releasing the spring tension. If the screw clamp doesn’t go far enough, release the other end of the pipe clamp and back that off- it’ll be under very low tension at this point.

To replace a spring, assemble the parts, back the clamp out as far as it will go, and then manually slide the far end of the clamp as far forward as you can. Use the screw clamp to finish compressing the spring, replace the retaining pins and screws, and there you are.