Hammerli AP20 Bolt Closing Adjustment

[Gwhite]

The college team I help coach bought twenty six AP20's in 2019 that we use to get students started. Other than a few initial problems, they have been very reliable.

We've started up again this fall, and a minor issue I've noticed in the past appears to be spreading and getting worse. On most of the pistols, when you lower the cocking lever, there it a bit of resistance as you close it, and then the cocking lever snaps down into place. It feels consistent with a toggle linkage going "over center", but mechanically, that's not the way it works. I don't have one in front of me, but the diagram shows a small shelf in the slot of the cocking lever that might provide that last little "step" in closing force. The resistance may be the O-ring on the bolt seating in the breech.

It may just be that we haven't kept that slot adequately lubricated, and the "step" has worn. Most of the time, the cocking lever will pop up just a little bit on firing, but it doesn't seem to affect anything. A few days ago, I heard a weak report from one pistol, and when I looked, the cocking lever was up by over an inch. I suspect it had opened up enough on firing that some of the pressure had vented out the breech. It may just be that the student didn't close it all the way, because I caught them doing later later on.

It doesn't appear that there is any way to adjust something to fix this. Unless I'm missing something, the only real cure appears to be to replace the cocking levers, which will be costly in time & dollars. Another possibility is that the bolt O-rings are getting worn. Those look even more involved to replace...

Has anyone else run into this, and is there a simple fix? I'm definitely going to grease the lever slots tomorrow when I'm at the range.

Thanks!

[m1963]

I have a brand new one, just out of the box, in my hands. It has a definitive half-cock, and full cock status. Perhaps look at either spring #78 having lost tension, due to wear? When enough tension is on the bolt the cocking handle should not pop up. I do not believe the cocking lever has anything to do with the issue you report. They really are great pistols. overall. We have 4, now. Please let us know what you find.

[Gwhite]

Once it's cocked, the striker spring #78 is held by the pawl system, and shouldn't have any effect on the cocking lever. I have a picture of the cocking lever that shows that the cross pin through the bolt should effectively "latch" into the front of the slot where it hooks backward slightly:

Cocking Lever Notch.jpg (53.02 KiB) Viewed 15268 times

What I don't know is what might prevent it from latching. If the notch is worn, I could see it would be a problem. Also, if the lever is prevented from going down far enough for the bolt cross pin to fully seat in the notch. The bolt has to provided some backward force to stay in the notch, and I don't know if that is just from compressing the O-ring, or if a spring is involved somewhere.

We've got a big match against Navy this weekend, but I'll try to check out a few pistols tonight at practice and see if I can figure out more of what is going on.

[Gwhite]

I checked over 20 of our pistols, and basically NONE of them actually "latch" in any positive way. The lever just goes down and stops. The only pistol I found that seemed to have any positive latching action is one I switched to left handed, and the lever is rubbing on the inside of the grip. That pistol has had very little use compared to most of the others.

There doesn't appear to be any significant wear on the "notch" at the end of the cocking lever slots. There is some variation in how much force it takes to work the lever, but that's about it.

I thought there was at least a small latching feel to the levers when they were new, but either I imagined it, or the levers were rubbing on the inside of the grips and that has all smoothed out.

I don't really care if it latches down or not, as long as it stays down. I am concerned about the lever popping up on firing to varying degrees. I'm going to have to watch a bunch of pistols in action. I want to see if I can identify ones that don't have the problem, and ones where it appears to be enough of an issue that it might be leaking air around the bolt when firing.

[brent375hh]

The o-rings don't have enough elasticity to change out?
By looking at the diagram that appears to be what provides rearward pressure since the barrel does not look like it has opposing set screws like Steyr.

[Gwhite]

Most air pistols require disassembly to change the O-ring on the bolt. I want to identify the pistols that pop open the worst & see if I can tell the difference. I can also contact the gunsmith at Walther/Umarex USA.