Recent content by MajorSylvester

Other tuning learning: I'm quite impressed by the velocity difference beween .217 and .218 slugs. Diameter is just increased by 1 thou BUT for the very same tune de velocity of .218 are 30fps less than the .217. Of course .218 generate more friction but I would't imagine such an impact on the...

1st hypothesis: good engineers are rarely good communication managers. 2nd hypothesis: marketing manager tells everyone to shut up

I' m one of those guys but it was due to my poor armourer's skills. Now I have tested the SPK extensively and I could get 39 fps more velocity or 20b less reg2 pressure for the same velocity as before. In the SPK I'm using the 2 spacers and the pin probe but neither the rubber ball and the new...

I spent the whole day testing disassembling and reassembling the rifle and shooting 100 slugs in my bullet trap. Here are the results and my key learning. Note1: I define the maximum spring preload as the preload you can achieve just one micro click before you can’t anymore cock the rifle...

Yes TDK, I agree with the 3 assumption you mentionned above for Keith and Norm rifle, but you are also assuming the open time is the same for both rifle, this may not be true since Keith have less reg pressure than Norm if the open time are the same the slug will get less energy and its speed...

Well I am not sure but I would bet it is just a question of open close scenario. Anyway the depth of the valve opening has an influence on the open time and the total air flow. See curves below. Scale and figures are not relevant and grossly exagerated.

TDK, I think it boils down to what hypothesis we use for the curves. Here is what I suggest: - the valve travel will depend about the initial speed of the valve. The valve will be subject to the force resulting from plenum pressure only. It means it speed will decrease until it reaches its...

Here is my preferred scenario, your #3. Sorry for my ugly sketch.

Or it could be like this:

Well, in the first scenario there is less "area under the curve", not more: the valve movement distance will be the same but it will open for a shorter time. The second scenario is not compatible with a higher valve speed as per my calculation. In my opinion the only scenario left is the third.

Well, yes and no. From my calculations above, the momentum will be increase by SQRT(.8/18.3)= 2.5%. Not much for sure but assuming this increase the slug speed by the same rate you could gey 25 fps extra on an initial max velocity of 980fps. This assumption is not really accurate since, like I...

Thanks for your messagre bigragu. I finally solved the issue: when I installed the power kit I wasn't careful enough: the 2 parts of the cocking block rotated also the front of the power plenum rotated. I took a while to realize this.The rotation of the cocking block could explains thev loss of...

Weight of 1 spacer = 0.44 grams = 6.79 grains

*** Warning: long and boring post*** I couldn’t help thinking of this spacer problem again and again. This morning I came up with a new explanation for the spacers. Sure, spacers don’t change the energy stored in the spring and therefore the kinetic energy of the hammer. It increase the mass of...

I will weigh the spacers when I'm back home at the end of the week.