This report covers:
- What did Vortek say?
- If only…
- Disassemble the rifle
- A final comment
- Relax the mainspring
- Cut off mainspring coils
- Install mainspring
- Thoughts before testing
Put on the coffee pot and grab a couple of your favorite doughnuts or crullers because this one will make your day! You may even want to call in sick or take a personal day for this one!
Today we dive into the HW 50S rifle and adjust the low-power Vortek PG4-Steel tune. First, let me tell you what I did last Thursday. While you readers ran around like wild people, chanting epithets against Vortek, I talked to Tom Gore, the owner, and asked him to read the blog. He did and told me the mainspring wire diameter in the kit I installed was correct, but the preload of two inches that he read in the comments was too much. So, reader Michael, here comes the answer to your question,
On the subject of amount of preload vs thickness of wire, would you say that in general the wire thickness contributes more to the power of the spring? Obviously coil diameter, which would be a factor in general, is not a variable here, right? (The composition of the steel probably makes a huge difference.)
Years ago I purchased a modded HW77. What attracted me to it was that the seller detuned it a bit with a new HW50 spring. It had a smooth shooting behavior last I tried it, and it is the easiest cocking underlever I’ve ever shot, by far. At the time I did not yet have a TX200, but my thought was that my HW77 probably was like a slightly weak TX with much easier cocking. I should dig it out sometime this summer, although usually either early heat, oppressive humidity, rain or Canadian smoke has prevented me from going out more than a few times.
I answered Michael thus,
Your question is one I have long pondered. I know that if the preload is decreased, the power drops a little and the cocking becomes easier. If the spring wire diameter decreases, the power drops quickly. The steel alloy makes a huge difference in power.
So yes, no and I don’t know.
What did Vortek say?
This is what Tom Gore told me. He doesn’t get much call for the lower-powered kit from the USA (no kidding!). Nearly all the demand for that kit comes from Europe. Because of that, his kits have the correct spring wire (see, shootski? Now aren’t you glad you didn’t fly off the handle?) but the overall length of the spring could be too long. He went into his warehouse and checked several kits and they all had the correct wire in their mainsprings.
He said he would send me out a lower-powered kit that met my requirements that same day or I could do what he was going to do — clip off a couple coils from the mainspring in my kit.
If only you readers had told me to clip off coils! This whole mess could have been avoided!
Calm down, readers Yogi, Roamin Greco, Siraniko, RidgeRunner, Frank Balistreri, and shootski, I’m just kidding. You guys did tell me what to do and several of you said to clip coils. I knew to do that, but I wanted to hear what the manufacturer said. He said two inches of preload was too much for the kit to deliver lower power. He told me to clip off two coils, which would remove about 20 mm from the spring length, so that’s what I decided to do. Why wait on shipping if that’s the best answer? So that’s what we’re going to do today.
Disassemble the rifle
With the barreled action out of the stock and in the mainspring compressor I began disassembly. Yogi, you asked about what I said last time in the Stop here! paragraphs, so this is for you.
Like you, I have difficulty disassembling Weihrauch air rifles that have the 4 locking tabs holding the back block against mainspring tension. I told you what to do in Part 10, and today I will show you step-by-step in greater detail. If you and I are talking about this there are plenty of guys having the same problem.
First, put some tension on the back block to take spring tension off those tabs. You won’t see anything move when you do this and the amount of tension is very important.
Look at the special tool I made from a nail to push those tabs out.
Now let me show you how that tool is used. Remember, I also said to insert a pin punch through the holes in the spring tube where the trigger pins were. That enables you to move the back block slightly as you push on the backs of the tabs. I would say 75 percent of the success is due to the tension on the back block and 25 percent is due wiggling the pin punch to align the locking tab holes.
This shows how to push out the locking tabs with the pusher tool. The secret to this is a combination of putting just the right amount of tension on the back block with the mainspring compressor and also wiggling the back block with the pin punch through the trigger crosspin holes.
When you get everything right the locking tabs can’t remain in their holes. They come out easily. On a new rifle they are harder to get out the first couple of times, but do what I have suggested and they will come out. One additional secret is to lever the pusher tool as you push each tabs out. Sometimes I find putting a screwdriver blade behind the pusher tool makes it easier to make it lever.
After the tab is out on one side, insert a pin punch through the hole and push out the tab on the other side.
A final comment
One last comment about the 4 tabs. They may not all come loose at the same time. The trick is to try to push all 4 of them out and when one cooperates, punch out the tab on the other side as shown above then go to work on the last two tabs. You may find that you have to relax or increase the tension on the back block ever-so-slightly for the other two tabs to come loose. And keep jiggling the back block with that other pin punch.
Relax the mainspring
When all 4 tabs are removed, rotate the back block to get the one back block tab out of the notch in the spring tube. Then relax the mainspring. When I did this, the back block had moved out by about 2-inches. That is how much preload is on the kit that was initially installed.
Cut off mainspring coils
Now I removed the mainspring from the spring tube. Then I had to get the top hat out of the piston end of the mainspring. I used a screwdriver to pry out the top hat.
Use a screwdriver to pry the top hat out of the mainspring. Go slow with this to not damage the top hat. It will come out, but the spring holds it tight! Do not grab the top hat with pliers; just slowly pry with a screwdriver.
The top hat is out. In this view you can see the separate synthetic washer the spring presses against.
I put the mainspring in a vise and cut off two coils with a Dremel tool.
After cutting off the spring I dressed the end of the spring with the sides of the cutoff wheel to remove all sharp edges left by the cut. I did not grind the end of the spring flat because the synthetic washer on the top hat takes care of that for me.
When this work was finished I cleaned and relubricated the mainspring with the red grease from the kit. There was still enough left for the job in the small container Vortek sent. Then I inserted the spring back into the piston and measured the new pretension.
Assemble the action
I now assembled the action and installed it in the stock. Testing was next.
Thoughts before testing
Because I am doing the work this way by removing coils instead of just installing a kit and calling it a day, I can stop wherever I want. Any time I want I can remove more of the mainspring. But I can’t put any of it back, so I have to go slow. This means I don’t have to automatically go down to a 7.5 foot-pound power limit if I don’t want to. That much energy would be the Air Arms 7.33-grain Falcon pellet leaving the muzzle at 678.74 f.p.s.
If I want a little more power I can have it. What I’m looking for is an HW 50S that isn’t hard to cock. So, what has the work I have just done produced? Well, the Falcon pellet now averages 815 f.p.s. That is a hair faster than the 810 f.p.s. the factory rifle puts out. At that speed the Falcon pellet puts out 10.81 foot-pounds. I know from testing that other pellets will be slower and have less power but this is nice.
The velocity low was 810 and the high was 820. That’s a 10 f.p.s. spread for 10 shots. I’ll take it.
The reason I sound like I’m smiling is because I am. This rifle now cocks easily and shoots dead smooth! The cocking effort is a measured 27 pounds — a 5-pound decrease from the factory and also the same decrease from the way it cocked when this kit was first installed. It’s now easy for me and I’ll take it.
This is a happy ending and I like happy endings. But we aren’t done. This rifle still wears it’s new-style stock that rules out the use of open sights for me, so on THIS rifle I will mount a scope! This will be the scoped rifle many of you readers wanted my HW 30S to be. I’ll scope it and test accuracy next.