Hammerli AP20's Won't Cock Reliably

[Gwhite]

The team I help coach just purchased 26 new AP20's & 8 spare cylinders. We had two leaky cylinders, which is no big deal. However, a couple of the pistols won't cock reliably. Initially, I thought it might be that they needed a little "breaking in", but the students have shot about 100 pellets so far. I also thought they weren't pulling back the lever hard enough, but I've tried one, and it's intermittent for me as well.

The cocking process on the AP20's gets tight towards the end, so it's a little difficult to feel the stop, but it's there. The pistols are acting as if the sear isn't quite engaging. There is no diagram of how the mechanism works, and the exploded diagram is a bit too "exploded" to see how the parts interact.

The manual talks about adjusting the "pawl", which I'm guessing is the sear. It may be that the sear engagement is too light, or that whatever stops the cocking lever isn't allowing enough rearward travel for the sear mechanism to "catch".

Does anyone have any experience with this issue? Without more info on the internals, I suspect we will have to send them back to Walther. I've had plenty of experience working on triggers, but only ones where I had at least a vague understanding of the mechanism to start with.

Thanks!

[David M]

Three things can cause these problems with engagement.
1 Sear engagement, too little
2 Second stage or sear pawl weight, too light
3 Trigger after travel too tight, not allowing engagement.
Start with increasing the after travel

There is no sear in this trigger, but a blocking bar. The Striker (47) is held back cocked by the Block (35)
engaged in the groove in the Striker. The Catch Lever(34) holds the Block up until the trigger moves it out of engagement.
Things to check.
1 Back the trigger stop (overtravel) off to allow plenty of clearance.(screw F) [unmarked screw above pawl spring 79]
2 Put a couple of turns on pawl spring to ensure engagement (G) [second stage weight].
3 Cock the pistol (unloaded), slowly turn the Pawl engage screw (E) in until the pistol fires.
4 This sets the release point, now if you are going to use a light 2nd stage weight(less than 100g), back the Pawl screw (E) off 1/4 turn minimum,
(maximum 1/2 turn) this will have a little second stage travel (creep). With a heavier 2nd stage weight (100-250g), back off 1/6 turn. This has less
2nd stage travel (crisp trigger) but needs the heavier weight to be reliable.
5 Now set the trigger stop, cock the pistol, wind the stop in until the trigger won't fire. Then slowly back off until it does fire (trigger point)
then back off some more to allow 0.015-0.030" trigger movement after trigger break.
6 Adjust the trigger 2nd stage weight to feel, then adjust 1st stage weight to +500g ISSF limit.
If it were my pistol I would set weight 350/150g (1st/2nd), 4-5 mm total travel with a small amount of 2nd stage travel and 1-1.5 mm after travel.

[Kallysan]

When my AP20 stopped cocking, I found the piece attached to my striker (no number on the diagram) that the blocking bar (35) locks onto had it's set screw backed out. I had to play with how far this piece fit onto my striker and re-tightened the set screw and it functioned again. I believe this is how the velocity is set at the factory.

[Gwhite]

Thanks for the info, David's especially. I hadn't thought about the trigger stop. In the absence of any feedback from Walther, I'll start with that & then try the pawl adjustment.

These are all very fresh from the factory, so I wouldn't expect to have to mess with any of the trigger weight adjustments. The trigger feels fine, it just won't go click about a third of the time. The worst pistol seems to have gotten fussier over time, so it may be that "breaking it in" broke it...

[Gwhite]

I'm still digging into this. We now have 3 pistols that have the problem to one extent of another. I tested one at the range last night, and got it to fail several times dry firing it normally. I took it home for more detailed analysis.

This morning, I removed the cylinder & took the grip off to see what I could observe, as well as to get access to the "pawl" adjustment screw. I cocked and fired it 20 times without a problem. Figuring that maybe there was an interaction with the grip, I re-installed that, and cocked and fired it 20 more times.

I had converted a different pistol to left-handed a while back, and noticed that the cocking action was rougher if the pistol was rolled over to the left so the action was horizontal. I tried that position on this pistol, and it locked up. With the grip off, I could observe that the "coupler" was always being caught properly by the pawl, so a pawl adjustment probably won't help.

Getting the action un-locked is a bit of a challenge. I haven't had time to experiment too much, but rolling the action on its right side, pulling the cocking lever all the way to the rear and tapping on the left side of the action seems to work. I'm going to work with it more this afternoon and see how far it has to be tilted to lock up, and if there is a simple & reliable way to un-lock it. I'm guessing that the degree to which it gets stuck may be related to how far it's tilted when it's cocked.

It appears that something in the action is loose enough that it can shift in in a manner that blocks the trigger mechanism if the pistol isn't held vertically. It may be that the trigger stop can be backed off to fix it, but I haven't had time to test that yet.

I'll update this as I get more info...

Update the 1st: The trigger stop had no effect on this problem. Whatever is going on appears to be a "break-in" issue, in that the more I jam & un-jam the mechanism, the harder it is to get it to jam. Even tipping it left & right, and tapping on it, it started locking up less & less often. It is now at the point where I've cycled the trigger over 100 times without a problem, and when it does lock up, simply recocking it purposefully un-locks it. I suspect there was a burr or something that was causing the problem, and the innards are now smoothed up from LOTS of firing (a couple hundred clicks at least).

Next step will be to see if the same holds true on the other two pistols. They are all fairly close in terms of serial number, with two of them having consecutive numbers.

[Gwhite]

I checked the other two AP20s that had been locking up. The shooter with the least troublesome one said it seemed to be resolving with use, and that he hadn't had any issues recently. His pistol also always responded to re-cocking firmly.

The 3rd pistol had been taken out of service because the trigger was locked up and no amount of re-cocking would free it up. I took it home and tried a variety of things that had worked before, The process that finally did the trick is detailed below. After that, I tried to jam it again by cocking it with the action vertical & both with the left side down & the right side down. 3 cycles on the right locked it up again, but re-cocking fixed it. 17 more on the right side were fine. I finished with 100 cycles vertical, and had no more problems.

Summary: Whatever is going on, the problem appears to be a "break-in" issue. Adjusting the trigger screws won't fix it. The biggest issue is that sometimes one will lock up and re-cocking won't get it un-stuck.

In that case, the trick seems to be:

1) Remove the grip to get better access to the side of the frame over the trigger area.
2) Cock the action firmly
3) Set the lever in the dry fire position
4) Hold the pistol horizontally with the left side down
5) Give the frame over the trigger section a firm rap with the plastic handle of the large hex key

I have no idea if all those steps are essential, and I only had a chance to try it once before the pistol got the message and decided to behave itself. I suspect you can probably get the desired effect without removing the grip and whacking the frame just in front of the grip.

[kbean]

I have a question for you... how did you get the grip off?
I got the fastening screw out and the grip rocks front to back, but I can’t get it to move down away from the frame. Any suggestions? Thanks!

[Gwhite]

They can be a tight fit. Just keep wiggling & pulling, and it should eventually slide off.

[Bandgap]

The pistols are acting as if the sear isn't quite engaging.

I thought I`d add my two cents to this topic. I had the problem with my AP20 that Gwhite describes above. The gun did not always cock when the lever was brought back to the vertical position. Usually, a single re-cock was sufficient to get the gun to fire. Occasionally, it required two re-cocks. The gun did not lockup completely at any point.

The Walther service department was very fast with their email response and detailed in their comments. They suggested I adjust the sear (pawl) per the manual (section 5.5.6, setscrew E). David M suggested a similar adjustment above,

Three things can cause these problems with engagement.
1 Sear engagement, too little
2 Second stage or sear pawl weight, too light
3 Trigger after travel too tight, not allowing engagement.

I followed the instructions in the manual. Now the cocking mechanism works flawlessly. So far I have shot about 20 pellets and about twice that many dry fire shots, no problems.

[B Lafferty]

On my AP-20, if the bolt that fastens the grip is too tight, this affects cocking making it difficult to cock the lever. I have no idea why this is, but it is.

[Gwhite]

I've seen some issues in the past where the grip screw on a pistol (not an AP20) was just long enough to interfere with the trigger system. Grinding a millimeter off the end fixed it. I think I've heard of Pardini SP's having this problem.