Two spring guides = two different max fps?

[tjcib]

Disco .22 with a stock spring with 3 full coils cut off.

I have tried two different spring guides (see pics below, sorry no side-by-side). One of them is a rivet that sits perfectly into the recess of the end cap. The other has a lip that is too wide to fit into the recess, so it has much more preload even without screwing it in. The rivet is slightly (1/8") longer than the other piece.

I am able to crank the power adjuster in with both of them until I cannot cock the gun. I then back it out until it finally cocks. At that "full power" setting the rivet gets a max power of 708 fps, but the other gets a max of 814 fps.

Now that would make sense to me thinking, "the longer spring guide (rivet) is "bottoming out" on the hammer causing it to not cock, rather than it actually being "coil bind" as the stopping point." The only problem is, it is the SHORTER spring guide that is getting the higher fps.

Anyone have any clue what is going on?

Some thoughts:
-Hammer travel distance is longer with the shorter guide, so more momentum.
-Rivet is narrower so it is causing some problem with the spring as it compresses by being off center

Here is the rivet:


Here is the other guide:

[rsterne]

The hammer travel distance is set by the distance between the trigger sear and the valve stem, so that is a constant.... My guess is that the larger OD guide, when screwed forward, hits the back of the hammer, I'm pretty sure the hole is the same size as the hole in the rear cap.... Therefore, you are not getting "coil bind" with the larger OD guide, but rather "hammer bind".... With the smaller OD guide, which fits inside the hole in the hammer, you can increase the preload more than with the larger guide until you really do experience "coil bind"....

Bob

[tjcib]

That all makes sense...but...My results are the opposite.

The larger outside diameter is getting the higher fps.

The smaller OD (that fits into both cavities) gets lower FPS.

It is really strange trying to wrap my mind around it.

[rsterne]

Sorry, no idea....

Bob

[tjcib]

You are correct that it is not coil bind. Did some more tests...

I cocked it with the "lower fps" spring guide at what is its max power. Once it was cocked, I turned the power adjuster in another half turn...of course it was very high tension, so I didn't try to go more...

Something is preventing the hammer from fully retracting after a certain amount of preload. It is not coil bind, and the guide is short enough that it shouldn't be "bottoming out" on the hammer.

I'll keep testing...