Breathing new life into a HW 45

Nick Stanning breathes new life into a well-worn HW 45 that’s been crying out for a little bit of TLC

The HW 45 isn’t the easiest airgun to strip down, but it can be done

You Will Need:
-Spring compressor
-Safety pin
-Allen keys
-Hand clamp
-Punch Hammer

Get your tools ready!

The Weihrauch HW 45 has been the iconic spring pistol of choice for many airgun shooters since the mid-1980s. It’s famed for its power and build quality, and that, along with its resemblance to its powder-burning Colt 45 namesake, has made it a bestseller worldwide.

But over 30 years on, what is it really like to live with? Does it deserve its reputation? Is it still a contender?

Well, for a start they are rarely full-power pistols – and don’t forget that’s 6ft lb for a pistol, not 12! This may seem like a surprise, but even with the gun crammed full of spring and dieseling like a good ’un, 5.5 ft lb is the most I’ve seen.

And the dieseling – what’s that all about? Huge detonations, smoke hanging in the air and cries of “I love the smell of an HW 45 in the morning!” are commonplace for some owners whose HW 45s have been around the block a few times. While this may seem like great fun, it doesn’t lend anything to your shooting accuracy.

Find the small hole in the locking rod and secure it by pushing a safety pin through the hole – this will keep the parts together and maintain the orientation of the sears

The example I have here is a typical well-used one: big smoke, big noise and big groups. In fact, at six yards with my wrist rested on a bean bag I struggled to keep all the shots on the target, let alone in the black, although it has to be said that my lack of pistol prowess and failing eyesight didn’t help much either.

Over the chrono a few problems soon became apparent: it was putting out just over 3ft lb with an extreme variation of over 30 feet per second! It’s clear that this gun needs some attention, so let’s see what a good strip-down can achieve…

The HW 45 isn’t the easiest airgun to strip down, but by working methodically and using the right equipment, it can be done. This is the method and order I use…

To strip

The TbT (Tinbum Tuning) Maxi Plus tuning kit includes a new spring

First, remove the grips from the gun: this will  expose the bottom half of the trigger arrangement, and most importantly, the anti-beartrap device. This is the trigger locking rod that comes down vertically, being pushed by the casing of the overlever.

If you look very carefully, you will see a small hole in it just below the crossmember it passes through. You must put a safety pin through this before going any further. Failure to do this will result in bits of trigger pinging around the room and a long battle with trigger sears trying to get them set right again. With the safety pin now in place, thumb the ‘hammer’ and allow the overlever to unlock.

At the front under the muzzle, you will find a small grub screw holding the hinge pin in place: loosen this, but do not remove it. Now you can drift the hinge pin out, and the lever and barrel can be removed and put safely aside. Next, the pin holding the rear of the compression tube needs to be drifted out with a suitable punch. Care must be taken here, as it is quite easy to slip and damage the finish of the pistol.

There is another Allen-headed screw under the frame: undo this and the compression tube can be removed. It may take some manipulation and encouragement, but it will come free. The frame can now be put aside: it won’t be needed until you rebuild.

Now that you have the compression tube out of the gun, you need to open it to get to the spring and piston. This is the trickiest part of the strip, as the spring and end cap are under considerable tension. You’ll need a spring compressor; if you don’t have one, there is a guide on how to make one on page 45 of Airgun Shooter 98.

The cocking lever and barrel can be removed from the 45 and put aside once the hinge pin has been drifted out with a pin punch

Place the tube in the compressor and wind the head in to take the spring pressure. It is advisable to use a hand clamp to secure the tube to the compressor to stop any movement. With the pressure taken by the compressor, you can now tap out the retaining pin, then carefully unwind the compressor and relieve the spring pressure. Finally you can remove the spring, guide and piston from the tube.

You will see that the spring guide is a one-piece steel item. Although it is usually a good fit to the spring, it will only support one end of it during firing, leaving the other end to thrash around creating noise and vibration. TbT makes a couple of tuning kits for the HW 45: one to fit your existing spring, the other including a genuine Weihrauch replacement spring. As the power was lower than expected and the spring had seen better days, I opted to fit the latter Maxi Plus kit.

The TbT kit uses a two-part spring guide compared with the one-piece original

You will see that rather than the single guide as found in the pistol, the TbT set has a two-piece arrangement: one to go in each end of the spring. There are also two slip washers – one for each end – that act as bearings and allow the spring to spin freely on firing.

The HW 45 in standard trim runs pretty much coil-bound: the coils are fully compressed when cocked. This is one reason why the recoil is so extreme: with the added preload from the twin guides and slip washers, it is likely the gun wouldn’t cock with the spring fitted at full length. I know this from experience, so I removed two coils from the spring and refinished the end before fitting it.

Other things to do while you’re in there are to degrease the piston and compression tube thoroughly; check the piston seal for damage and replace if necessary; and remove any burrs and sharp edges from the slots the cocking arms run in.

It is advisable to use a hand clamp to secure the tube to the compressor to stop any movement

Once everything is cleaned and ready, it’s time to rebuild. Another reason for the HW 45’s recoil is its habit of dieseling: to avoid this it is vital that you don’t over-lube the action. The TbT Maxi Plus kit includes a pot of high-moly paste: this is ideal, as it’s very thick and very sticky. To lube the piston, you just need a tiny amount on your fingertip then rub it into the outer body of the piston, taking care not to get any on the piston seal. The effect you are going for is to leave the piston looking discoloured rather than having a visible layer adhered to it. Use similar amounts to lightly cover the spring, just wiping a tiny amount over it. Then rebuild in the reverse order of the strip-down guide. Take care when compressing the spring back into the compression tube: it will want to twist, so control is vital.

Results after stripping

This is what we’re after: the HW 45 has now been disassembled far enough for the compression tube to be removed

Now the gun’s back together, it’s time to see how it’s performing. The initial feeling is of far less recoil, less noise and a total lack of smoke! Over the chrono, the power and consistency are both improved, with the average power now being 4.9ft lb, with only 8fps variation between shots.

Back out on the range, the group is now huddled nicely within the black. Shooting spring-powered pistols is all about having fun. The HW 45 will never be a ‘restful’ pistol to shoot, but it’s more rewarding now that hitting the target is a realistic expectation.

If you want a spring-powered pistol, this is still one of the best options available. But we can always make the best that little bit better.

This article originally appeared in the issue 102 of Airgun Shooter magazine. For more great content like this, subscribe today at our secure online store:

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Posted in Features, Gear, How to

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