Need some help with a B3

[rr_shooter]

I purchased a B3-1 from ToolsNow and I’m in the process of modifying the stock to increase the LOP.  While the action was out, I figured I’d try my hand at a deburr/polish/lube.  During re-assembly, I installed the longer mainspring from a QF-2 maintenance kit.  I also installed a single nylon washer inside the piston to increase the pre-load (probably unnecessary, but easy enough to remove if it became a problem).  I put the action back into the stock, and went to try it out.

When I attempted to cock the rifle, the sear did not engage the piston.  My first thought was that the nylon spacer was putting the spring in a coil-bound position, preventing proper sear engagement.  I took it apart, removed the nylon spacer, and re-assembled.  Unfortunately, I still have the same problem.

If I gently place my finger on the side of the trigger while pulling back on the cocking arm, I can feel the trigger move slightly at the end of the stroke, but I feel no “click” as your normally hear/feel when the tab on the piston engages the sear.  This makes me think I still have a coil-bound situation with the spring.

I feel confident I have put everything back together correctly.  I performed a trigger polish on my other B3 a while back, and had no issues upon re-assembly.  I was also careful to maintain the existing geometry on the sear and piston during polishing.

I intended to try the re-assembly using the stock spring, but ran out of time last night.  I will try that tonight to see if that change alleviates the problem.

Has anyone else experienced this issue when using the spring from the QF-2 kit?  I purchased two of the kits, and the length of the springs in the two kits is different (I’m using the longer on in this case).  Is there a “correct” or maximum length for B3 springs in these kits?  Perhaps someone has information on the maximum length of the spring in the cocked position.

Thanks in advance for the help.

[mikeiniowa]

do a coil count, if the new spring has more coils then it's binding.....if not then it's in the trigger....

[shadow]

That main spring you installed should be ok since I use the same spring in my B's. Ok let's move to the trigger and sear, there's a spring there also that attach the trigger to the sear. If that little L shaped spring is bent to much it won't apply enough pressure to the sear and keep it in place with the piston when the B is cocked. Now it may be the piston itself if the area where the sear engages is too shallow the sear will not lock in and hold the piston in place. Do not alter the shape of the piston in this area, a slight polish is ok but changing any angles may refuse to let the sear engage and hold. Another thing to look for on the piston is when you install it make sure that all the slot's line up, flip the action over and look through the action slot. You should be able to see the piston slot and even the edge of the area where the sear engages in the back of the piston. That area should sit centered in there which give the sear a nice even area to engage. Keep us posted on what you find. Ed

[rr_shooter]

Ed & Mike -

Thanks for the input.  I installed the stock spring last night and felt the sear engage at the end of the stroke, but it would not hold.  As soon as I released pressure on the cocking arm, the piston would move forward.  So the problem is obviously with the interface between the sear and the piston.  As I can hear and feel the sear engage, I don't think the problem is with the spring at this point - I think that i removed too much material from the piston and/or sear face in my polishing efforts.  I have a couple more sears from the maintenance kits, and I plan on trying those to see if they hold.

The other thing I noticed is that when the piston slot is lined up with the cocking arm, the flat spot on the rear of the piston seems to be turned slightly.  In other words, the face of the flat spot would not seem to be matching up exactly with the flat surface on the sear.  Didn't take any pictures, but may tonight if I can't solve the problem with one of the other sears.

I think I already know the answer to this, but I don't suppose there are any sources for replacement pistons for B3 (besides buying a new rifle).

Thanks for the advice.

[shadow]

That flat area near the sear should be centered for best result's. Another thing to try is to keep cocking it to see if the sear will settle in and catch. I had to do this 5 to 6 times on several of my shooters until the sear caught and held. Once it get's a wear spot on the piston it will settle in. Make sure to keep hold of the cocking arm and when it does catch, load a pellet and shoot into a safe area. Also if it does catch return the cocking arm slowly, they can go off before the cocking arm is back in it's clip.Ed