Author: timinder [Tue Feb 05, 2008 4:38 am] Post subject: Setting up the S200 trigger.
I think the final weight being pretty heavy is due to the design of the mechanism. It's not a true two stage trigger, but not a single stage one either, more a 'one and a half' stage! This is because unless the rear spring is extremely strong, once you have pulled the first stage, the sear stays in position even when you release the trigger, as it's being held there by the full force of the firing spring acting on the striker (part 25 in the AA parts list). I've managed to fettle mine and I think it's about as good as I'm going to get it. Put the kettle on and make yourself comfy - this is a pretty long post! Here's what I've done:
1. The trigger return spring (part 68, which sits between trigger bar and sear) on mine was so strong that it would actually fire the action before the second stage grubscrew could! I substituted this for the spring which controls the trigger weight (part 60, sits between rear of the trigger guard and rear of the sear). This gives a nice weight to the first stage.
2. Once you have sorted the above, you will notice there are actually about 4 stages to the trigger! This is caused by the tips of the adjustment gruscrews having squared off ends. I removed the screws and ground and polished the tips into a dome shape so that each has only one point of contact on the sear.
3. Remove the sear and shape and polish the rear face. The contour of the sear is basically a radius with its centre where the pivot pin is located. There should be a sharp edge between this face and the 'top' face of the sear, where it engages on the striker (part 25)
4. Tidy up and polish the step in the striker where the sear tip engages on it. It's also not a bad idea to form a little flat on the bottom of this part so that as the sear disengages, it spreads the force over a slightly larger contact area.
Stages 3 and 4 are necessary, as any 'grittiness' you feel when operating the trigger is due to roughness on these two faces as they slide over one another.
5. Replace the trigger weight spring (part 60) with a likely looking spring either from something such as a ballpoint pen (!) or the correct part from AA. To increase the weight, screw into the rifle, to decrease, unscrew, but be careful not to go too far or it'll ping out and disappear forever! You may be tempted to remove this for ultimate lightness, but don't, as its other task is to make sure the sear engages in the face of the striker as you cock the action.
6. Now, for a two-stage feel, adjust the two grubscrews as follows (best to remove the air reservoir before this bit if you haven't already!):
- 6.a. Unscrew both so that pulling the trigger will not fire the action.
6.b. With the action cocked and trigger pulled fully back, slowly and carefully screw in the front grubscrew until the action just fires (keep your fingers out of the way of moving parts!) and back off 1/8 to 1/4 turn.
6.c. Re-cock the action and pull the trigger again, if you've done the above correctly, it will not fire. That's your first stage set.
6.d. With the trigger held fully to the rear, carefully screw in the rear grubscrew, again, until the action just fires. For safety's sake, screw in another 1/8 to 1/4 turn. That's the second stage set.
6.e. Test the trigger with the gun reassembled. You can tweak the final pull off weight now with the rearmost grubscrew, but be aware that this is only able to fine-tune the weight, the real determining factor is the friction between the sear and the striker. I believe that this mechanism was originally designed for either pistol or short range target rifle use, both at 6 ft/lb and so the main spring (and thus friction in this area) would enable a much lighter trigger weight.
- Firingmechanism.jpg (42.75 KiB) Viewed 5998 times