Weihrauch HW45 – Trigger Adjustment

Last week, I acquired another, yes, a fourth HW45 air pistol. “Four!” you say? Yeah, I must be a magnet for them. I’ll go into my reasons in another post. Anyway, whilst I had all four together I checked them over for variations and chronographed each of them to see how they compared.

Immediately I noticed that each trigger was configured differently. Probably as they were all pre-owned pistols, each owner had fiddled with the trigger adjustments. Well, those tiny grub screws in the trigger blade are very tempting.

two-stage trigger

Some of the pistols had a definite two-stage trigger whilst another had no first stage at all. The second stage on the fourth was so far back that it almost wouldn’t fire. I knew from those early teenage days (no I’m not that old for my memory to have faded) that the HW45 trigger can be sublime. Especially so for a spring air pistol. So I decided I would adjust them all correctly.

Achieving the correct trigger adjustment is a very important step along your journey to achieving accurate shooting. A poorly adjusted trigger cannot be a consistent trigger. An inconsistent trigger leads to uncontrolled and inconsistent shooting.

as useful as a chocolate teapot

First of all, I consulted the official user instructions only to find that it was about as useful as a chocolate teapot! The user instructions described the upper screw as the “trigger slack” adjuster. It merely states that turning it left or right shortens or lengthens the slack. If you’re not confused already, the instructions for the lower screw will seal the deal. The lower screw is described as the “let-off” adjuster. Turning left or right makes it “softer” or “harder”. Well, quite frankly, whilst it does control the “let-off” point, using the words “harder” and “softer” far from describe what it actually does. Perhaps this is a matter of “lost in translation” from German to English.

Somewhat bewildered by the “official” instructions, I searched the internet for a guide. Now you would think that as this pistol has been around since the mid-1980s that someone would have written a definitive guide. I couldn’t find one. Sure, there were some dribs and drabs about screwing the adjusters all the way in and then back out a turn or so. Some mentioned that adjusting one screw affected the other and vice versa. But there was nothing definitive. Nothing explained the mechanism or the process clearly and concisely. Well, there was only one thing to do. I’d have to work it out for myself.

bewildered by the “official” instructions

Luckily I had four HW45 air pistols at my disposal. Thus I hope that the guide covers all, if any, variations of the pistol’s trigger. The four pistols range from as early as 1987 up to 2010 and so should include both early and recent models. Only one of the pistols varied slightly in comparison to the others. The majority of the pistols had shouldered adjustment screws. This means they can be screwed into the trigger blade until they hit a hard stop. However, one of the pistols had standard adjustment “grub” screws without a shoulder. If you used the method of screwing these in all the way, you might end up losing them inside the pistol. I didn’t fancy stripping a pistol down to retrieve them so I decided not to test this theory! Besides, as you will find out, this is unnecessary and I suspect makes trigger adjustment more complicated than necessary.

So, without further rambling, here is the procedure!

Step 1 – The Adjusters

There are three adjustment screws in the HW45 despite the manual only revealing two. Two can be found inside the trigger blade and are accessed through a hole in the trigger guard. The upper screw, the one nearest the barrel, is indeed the “slack” adjuster. It can probably be used to adjust the length of the first stage although I found it unnecessary to adjust it any further than removing the slack or free-play of the trigger.

The second, or lower screw, adjusts the second stage “let-off” point. Rather than making it “harder” or “softer” as stated in the user instructions, it is used to set the length of the second stage. Too much adjustment of this screw in either direction may make the first stage vanish.

The third adjuster screw is hidden within the grip of the pistol and is accessed through a hole in the heel of the grip. This screw adjusts the “pull-weight” of the trigger. Adjusting this makes the trigger feel lighter or heavier to pull. Removing one of the grips will help you see the screw and guide the allen key into position.

Step 2 – Starting Positions!

Unscrew both of the trigger blade adjustment screws so that they are only just catching the threads, i.e. almost fully out. Set the pull-weight adjuster in the grip until it is flush, or level, with the underside of the grip cross member (the part of the grip it is screwed into).

Step 3 – Eliminate The Trigger Slack

You should find that the trigger is quite “floppy” or slack and there is no spring pressure to return it to its forward position. You may need to remove the Allen key adjuster to feel this. It should be very prominent. If there is no free play, you might not have unscrewed the adjusters in the trigger blade enough.

Now screw in the upper adjuster, the one closest to the barrel, until the slack is just removed plus a quarter or half a turn. Try adjusting the screw half a turn at a time until you find the slack is eliminated. Then back out a quarter of a turn. If the slack returns, screw it in an eighth of a turn. The idea is to find the point where the slack is just eliminated. Then screw the adjuster in half or a quarter of a turn.

You may need to remove the Allen key each time you test for slack. Once set, there should be no need to adjust this screw again – ever!

Step 4 – Set the Second Stage “Let-off” Point

During this part of the adjustment, it will be necessary to cock the pistol to test the trigger. However, one of the nice features of the HW45 is the ability to cock just the trigger and not the piston. So, where you are directed to cock the pistol, just open the hammer catch to open the breech, then close and lock the breech again. This will set the trigger so that you can safely “dry-fire” the pistol without fear of damaging it.

Go ahead and cock the trigger. Then slowly screw in the lower trigger blade adjustment screw until the sear releases. Try not to push the trigger whilst you make the adjustment. Once the trigger releases, back out the screw one turn. If you find the adjuster reaches its limit before the sear releases, don’t worry and don’t force it. Just back the screw out one turn.

Now test the trigger. As you slowly pull the trigger you will reach a stop or “detent”. It should be possible to pull the trigger past this detent and release the sear with slightly more pressure. These are the two stages. One before the detent and the second after the detent.

Step 5 – Fine Tuning

Now that you configured a basic two-stage trigger, let’s fine-tune it further. We are aiming for a two-stage trigger that can be held indefinitely at the first stage and then release the sear with just the slightest pull.

Unscrew the lower adjuster half a turn. Remove the Allen key, cock and test the trigger. Repeat until the detent is no longer felt, i.e. the sear releases without reaching the first stage detent.

Now screw the lower adjuster in a quarter of a turn at a time until the first stage detent returns.

Then begin to back it out again an eighth of a turn at a time until the detent is lost once more. Then back in just one-eighth of a turn. The goal is to find the limit of the first stage detent using smaller and smaller adjustments. You could continue using smaller than one-eighth turns if you wish although I found it unnecessary.

You may find that you reach a point where the sear appears to stick at the detent point and will not return to the forward position under spring pressure when you release your finger. If this happens, screw the adjuster in slightly.

You should now have a finely adjusted second stage where the slightest, shortest pull at the detent point will release the sear.

Step 6 – Pull-Weight

The final step of the adjustment of the HW45 trigger is the pull-weight. Adjusting this is a simple affair and should not affect any of the adjustments you have made so far. If you prefer a light trigger, unscrew the adjuster in the grip. If you prefer a heavier trigger, screw it in. You can do this one turn at a time or half a turn at a time if you wish as this isn’t as sensitive as the previous adjustments. Just make sure that each time you make an adjustment that you test the trigger.

You may find that the sear may stick at the apex of the mechanism. This is sometimes felt in the trigger as slack or you may notice some creep in the sear at the detent point. Should this happen, you can correct it by either increasing the pull-weight slightly or slightly screw in the lower adjuster in the trigger blade.

Step 7 – The Bump Test

Finally the safety check or the bump test. If you’ve followed the guide correctly resulting in a two-stage trigger, it should not be possible for the sear to release accidentally, i.e. a hair-trigger! To give you confidence that the pistol will not accidentally fire, cock it, then thump the heel of the pistol onto a hard surface covered with something soft to protect the finish of the grip. There’s no need to whack it hard as though you are driving a nail in with a hammer. Doing so will only damage the finish of your pistol. All that is needed is a firm bump to shock the sear. It should not release! If it does, then maybe you have set the lower adjustment screw out too far. Adjust it in one-sixteenth or eighth of a turn. Or maybe you have set the pull-weight too light. Adjust that in half a turn perhaps. Just make one adjustment at a time only.

However, of the four pistols on which I have used this method, none of them failed the bump test.

Now you should have a finely adjusted HW45 two-stage trigger with a pull-weight of your liking. Your accuracy and groups should improve if they’re not already top draw! If they don’t, try a looser grip and practice your breathing technique – exhale, relax, hold aim and trigger, squeeze, fire, follow through.