Hammerli 480K Trigger Weight Screw is Non-Existent?

[Gwhite]

The MIT collegiate team has a number of Hammerli 480K air pistols. Most were bought 2nd hand, and are of unknown vintage. We tested the trigger weight on several pistols yesterday, and a couple were marginal.

I adjusted one according to the manual, with no problem. There are two screws visible behind the trigger, and the top one controls the weight, and the bottom one controls the after-travel. No big deal.

When I got to the second pistol, I had a shock. There IS NO TRIGGER WEIGHT SCREW. I'm not saying is fell out & got lost, I'm saying there is no hole or any sign of an adjusting screw. There is a screw in the same location as the trigger stop screw, and sure enough, when I tried screwing that in, the pistol stopped firing.

I've checked all of the documents I could find on-line, and there is nothing that indicates this variation in the design. I didn't have time to pull the grip off & look, but I've got to assume there is an adjustment SOMEPLACE.

Does anyone have any info on this version? Some of these may have been converted from 480's, but the 480 manual shows the same trigger design as the 480K (and the 480K2). We have at least 4 of this sort of 480K, and I checked the serial numbers. They are all around 95 - 04000.

Thanks!