Theoben Rapid Forum

Well first here is a photo of a diagram of the Mark4 trigger:
(https://photos.imageevent.com/scl_electronics/gun/air/websize/Mark4_1_.jpg)

So first let's go over the screws in the diagram. Starting from Left to Right:

1st screw will adjust the Overall Trigger pull Weight!

2nd screw (first behind the trigger) this will adjust the 1st stage!

3rd screw (second behind the trigger) this will adjust the 2nd stage!

4th screw is to adjust the Amount of sear engagement. You shouldn't have to touch this unless for some reason you don't have enough sear engagement (your gun won't cock all the time! Even after follow these instructions!)

For Minor adjustments, this usually involves the 2nd stage. Only the 3rd screw needs to be adjusted. If the 2nd stage engages too early, you will experience a lot of creep after you reach the 2nd stage, before your Rapid fires. Turn the 3rd screw counter (anti)-clockwise. Only adjust the screws by 1/8 of a turn at a time!!! But if your rapid fires before you reach the 2nd stage, or the 2nd stage is intermittent (vague), then the 3rd screw needs to be turned clockwise!

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To restart trigger adjustments from scratch, back off the 3rd screw completely

Cock your Rapid. Push the trigger blade forward. While holding the trigger blade in the Forward position. Screw In the Second Screw until your Rapid Fires!! Now Screw Out the Second Screw 1-1/2 full turns! This will give you a good initial position for the trigger break

Now check the position of where the trigger breaks. Adjust the Second screw accordingly. Clockwise (In) to shorten. Counter(Anti) Clockwise(Out) to lengthen.

If you have shorten the Trigger pull, check the Safety for full Engagement . If  you are CONCERNED and want a fully operating safety. You will need to lengthen the 1st stage pull. Turn the Second Screw Counter(Anti)-Clockwise(Out) by 1/8 of a turn until the safety fully engages.

Now dry-fire your Rapid. Note the position where your Rapid fires. Adjust the 2nd screw according to where you want your gun to fire (amount of 1st stage travel). Clockwise for less travel (take-up), counter (anti)- clockwise for more travel!

**NOTE..If you try to reduce the Length of First Stage Travel too Much. You can disable the operation of the
Safety!!**

Next we adjust the 2nd stage. Use the same instruction for the minor adjustment here. You will adjust the 3rd screw so you will have a positive 2nd stage feel!! You will adjust the 3rd screw so the 2nd stage engages just prior to the point where your rapid fires!!

Finally for the overall trigger pull weight adjustment, you use the 1st screw! Turn the screw Clockwise to
Increase the pull weight. Counter (anti)-clockwise to lessen the pull weight!!!

***Any time you adjust the Trigger system of any gun Remember to TEST and RETEST!!!!!. An unsafe trigger is a disaster waiting to happen!!!***

I hope this helps!!
Stuart

Here is the Pdf file of this Post...
https://photos.imageevent.com/scl_electronics/gun/air/Adjusting%20the%20Mark4%20revised%20.pdf