Bit by the tuning bug again!

Many thousands of pellets have flown downrange since I’ve written here. In that time, I’ve purchased a Beeman QB78 and converted it to PCP. It has topped out as a 33 FPE monster, but I’m not here to write about that right now. I made the mistake of picking up and shooting my B3-3 the other day and decided I needed to go back to my springer roots.

I have break barrels and underlevers, so I decided it is time to get a side lever. Do you know how hard it is to find an affordable side lever? Diana seems to be one of the few companies still making them, but I don’t like to spend over $400 on an air rifle when I can have fun tuning three or four for the same price. Luckily for me, Mrodair had a side lever more in my price range.

Today, I received a B5, a Chinese spring piston AK-47 looking thing. Mine is in .22 and is almost all wood and metal construction. The only plastic I see on this airgun is the sides of the folding stock and some grip material to make the side lever more comfortable. Like most guns from overseas, there was cosmoline and some unknown oil everywhere.

My new B5 in .22
My new B5 in .22

I ran a couple patches through the barrel and a shop rag over the exterior and loading area. I then mounted a dovetail to picatinny rail and topped it all with my UTG 4×32 AO scope. I decided to test it out initially with CPHPs to work out the bugs. The cocking was the smoothest out of the box I’ve ever experienced with a cheap springer.

Then I took aim and squeezed the trigger. Must be on safe. No, it isn’t on safe. I took aim again and squeezed the trigger, this time much harder. Much, much harder! This thing must have the heaviest trigger in the world, I’d guess it broke around 15 pounds. If I don’t do something about this trigger, my finger is going to look like Quagmire’s arm after he discovered the dirty side of the internet! (If you have a devious sense of humor look that up on YouTube)

After a few dozen shots, I decided it was time to get a benchmark on accuracy before I tear it down, chop it up, and tune it. Most of my Chinese airguns really like RWS Hobby pellets, so I decided to use these for testing. I set up a grid target at 10 yards and took my favorite seated position. If you click on the picture in this post, you’ll notice I circled the group in red.

A half inch group at 10 yards with the worst trigger I’ve ever squeezed and no tune! I’ve got a real diamond in the rough here and I’ll be sure to update this site as I make progress.

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Installing Chairgun Pro on Linux

If you are serious about shooting airguns accurately, you know the value of ballistics software. One of the most popular applications out there is Chairgun Pro. It is available for Mac, Windows, Android, and IOS. What about us Linux users?

First, I’d recommend installing on Android or IOS if you have devices that run those systems. It is a great portable tool to have handy. The desktop version has a lot more functionality, so let me show you how to get it up and running on Linux.

To begin, you will want to install Wine, the Windows compatibility layer for Linux from your distribution’s software repositories. For Ubuntu based systems, you will open a terminal and type the following:

sudo apt-get install wine

Assuming your installation of Wine goes trouble free, the next step is to download Java for Windows. I used version 6 update 43, found here: http://www.oldapps.com/java.php. Your browser might warn you about downloading this. I’ve used that download for a long time safely, but your mileage may vary. It probably wouldn’t hurt to run a virus scan on it.

I then downloaded the latest version of Chairgun Pro for Windows from here: http://www.hawkeoptics.com/chairgun.html.

We now have everything we need for our installation. I extracted the Chairgun Pro installer into my download folder:

All files in my download folder.
All files in my download folder.

The next step is to launch the Java installer and answer all the prompts until Java is installed.

Installing Java for Windows
Installing Java for Windows

Once Java is installed, we are ready to install Chairgun Pro. Launch it’s installer and answer the prompts until it is installed. I go ahead and answer yes to creating a desktop icon so I can have convenient access to it.

The Chairgun Pro installer
The Chairgun Pro installer

At this point, I now have a desktop icon that I can double click any time I want to do range functions with my pellet rifles:

Creating a range card for my B-3 on Linux
Creating a range card for my B-3 on Linux.

Keep in mind that this software is virtually worthless without a chronograph. I recommend the Shooting Chrony F1, I’ve had mine for 12 years and it is still running strong. There some smartphone apps out there, I’ve played around with them, and found them to be fairly unreliable. Several people have found DIY ways to make chronographs as well, so that may be a route you would look into if you don’t wish to shell out just under $100 for a F1.

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Fixing my Center Point Scope

My Umarex Fuel ate the scope it came with alive. I replaced it with a Center Point 4-16×40 AO scope with illuminated reticle. I’ve been shooting with that scope for about a year now, and several thousand shots later, it has held zero flawlessly. The other day, however, I went to use the illuminated reticle and here’s what I found:

My scope failure
My scope failure

The dial to control the illuminated reticle had its screws vibrated loose from the recoil of all my shooting and was just hanging by the wires that went to the illuminator. I carefully disassembled the dial to get to the screws.

The guts of the illuminated reticle
The guts of the illuminated reticle

Note the ring on the bottom right. I used a small screwdriver to rotated it out of the housing. The round circuit board came out from underneath it. Here’s a view of the dial with the above components removed:

Inside the dial
Inside the dial

I then removed all six screws seen above. This allowed me to remove the dial, exposing the three loose screws.

Nip this problem in the bud
Nip this problem in the bud

To hopefully prevent this from happening in the future, I applied blue Loctite to all screws as I reassembled everything. After 24 hours, it should be ready for several thousand shots more. In the meantime, here’s a view through the scope after reassembly:

View through the scope after repair
View through the scope after repair

In case you haven’t seen it already, here’s a video showing how you can make a scope to cell phone adapter for any phone you can get a hard case for:

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New .25 Dart

Building accurate, reliable airgun darts is a real challenge. After dozens of designs, I have finally found one that produces consistent results, stabilizes quickly after leaving the barrel, and packs a real punch. Here it is:

My best .25 dart design so far
My best .25 dart design so far

Total weight is 80 grains. At 1000 psi, these travel at 355 fps for a quiet shooting 22 fpe. At 3000 psi, these come alive at 600 fps and 64 fpe. Shooting into a trap at 1000 psi, the darts can be reused dozens of times.

Here’s what went into the above design. A stable dart will be forward heavy. That’s why I added three nuts to the front.

An accurate dart needs to stay centered in the barrel. To achieve this, I took some .25″ od poly pipe to use as a main body. The tail is made from the same material.

An accurate dart has a tail that doesn’t get knocked around until impact. The tail is held in place with hot glue and a nut. The nut keeps it in place, even with a 3000 psi fill. The tail is cut, dividing the tubing in four equal parts that are flared out to provide drag stabilization.

A powerful dart forms a good seal with the barrel. Between the poly pipe body and tail, not much air can blowby. The dart has to be pushed down the barrel with a ramrod to load.

I hope this design gives you some ideas should you choose to build a dart shooting airgun.

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.25 DIY Airgun Project

It’s been a long time since I’ve built a homemade airgun. Recently, I purchased a Barska 4500 psi PCP hand pump. This gave me the incentive to get back into doing my own builds. So far, I’ve made the barrel and action, and have mounted it to my test stock:

My .25 airgun in its infancy
My .25 airgun in its infancy

Let’s watch a couple of shots with it, first with a .22 pellet in a patch:

Not too impressive. I’m still deciding if I’m going to leave it smoothbore. If so, darts will be my ammo of choice. Here’s a test shot with a dart:

By adding an o-ring to the head of the dart, the velocity is boosted to 790 fps, yielding 64 FPE! The o-ring also improves the ammo to bore fit, which should translate to better accuracy.

Nail darts, the o-ring makes a huge difference in efficiency.
Nail darts, the o-ring makes a huge difference in efficiency.

As you can tell, the darts here are very simple. They shoot reasonably well, especially considering the nails are not well made. Here’s a 20 yard group I shot:

20 yd. offhand group at 1200 psi
20 yd. offhand group at 1200 psi

Not too bad, but I really want more. Actually kind of impressive when you consider that the action is held to the stock with four dollar store zip ties. Another problem with this design is the lack of stability when shooting at higher pressures. I’ve been working on a new design that shows great promise when shooting at higher pressures as well as a variety of ranges. Here’s a sneak preview of it:

New dart design
New dart design

I’m going to continue with ammo testing until I’m satisfied. Having extensively tested the action, its time to build a proper stock and firing mechanism. I’ll keep posting updates as I make progress.

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The B3-3 Project

Way back, somewhere around 2004 and 2005, I bought a .22 caliber Chinese B3-3 air rifle. It was purchased primarily to introduce friends to air rifles. The only modification I made to it was to sand its awful stock down and coat it with black truck bed liner. Kinda gave it a tacticool look.

After several years of neglect and moves, here’s how it came out of the gun safe:

B3-3 with truck bed liner stock
B3-3 with truck bed liner stock

The stock had a few scratches and who knows what happened to the rear sight. I checked the barrel, it looked nice and clean, so I decided to chronograph it. The shots all fell around 425 fps using 14.3 gr. Crosman Premier hollow points. Not impressive, but pretty typical of these airguns.

Since this airgun is so low power, the barrel can be cut down a bit to improve velocity slightly. The barrel was then recrowned. I also cut the underlever to match. To improve the looks and ergonomics, I made a “muzzle brake” out of a piece of 1/2″ schedule 80 PVC pipe and a cover on the underlever out of 1/2″ cpvc pipe.

Beginning modifications
Beginning modifications

The PVC parts are heated until soft with a heat gun. This also expands them, allowing them to slip over the metal parts. When cool, they shrink, making a tight fit.

The breech seal was in pretty poor condition. Upon inspection, I realized that the transfer port was way too large. So large, that a 3/16″ drill bit slid in with room to spare. To fix this, I drilled out the port to 5/16″ to make room for a new port.

I constructed the new port by taking a 5/16″-18 bolt and drilling a 1/8″ hole through the center. I then cut a piece off the bolt that fit flush on both sides of the compression chamber. Here’s everything ready for assembly:

New transfer port waiting to be installed
New transfer port waiting to be installed

I used JB Water Weld epoxy putty for the adhesive. The advantage to putty adhesives is that they don’t run, creating a mess. The last thing I needed was adhesive sticking to the walls of the compression chamber. Here’s the new transfer port installed:

Transfer port installed
Transfer port installed

I then installed the new breech seal into the end of the compression chamber. At this point, I added a new spring, polished, then lubed everything up. I added a greased washer to the piston and spring guide to serve as a bearing surface and to increase spring preload a tad.

All these modifications have brought me up to a smooth cocking and shooting 500 fps. Still no powerhouse, but a gain of 2 foot pounds of muzzle energy out of a bit of elbow grease and a couple of locally sourced parts is nothing to sneeze at. It also makes this a good option for small game hunting out to 25 yards.

One problem with cutting down the cocking lever was not having a latch to secure it in position. I looked through my parts bin, but I didn’t have any latches that would work. I did find a neodymium magnet and decided to give that a shot. Again, JB Water Weld came to the rescue. I used it to attach the magnet to the underlever grip and blend it in:

Underlever grip with magnetic latch
Underlever grip with magnetic catch

This magnetic catch works so well, I can’t believe that airgun manufacturers don’t use this. The next phase of modifications involved making the rifle look better and to mount some sights.

I sanded down the action and barrel and coated it with cheap flat black paint. A clear coat was then sprayed on. The bed liner was left on the stock and a flat white paint was added. I then shot it randomly with flat black to give it a winter camo look. That was also covered in clear coat. The result came out quite nice:

To securely mount optical sights to the airgun, I ordered a dovetail to picatinny rail. This rail attaches to the dovetail groove in the action and secures with 3 screws. On the top is another screw to lock the rail in place.

I don’t have a scope yet for this airgun, so I decided to mount a much neglected red dot sight:

BSA 5 MOA red dot mounted
BSA 5 MOA red dot mounted

Note the finish on the action. Sure doesn’t look like the cheap paint that it is! Of course, looking pretty doesn’t matter. In the end, being able to hit your target is all that matters. I brought my newly finished airgun to my 10 yard range to test it out:

My humble 10 yard range
My humble 10 yard range

I used a rolled up sweat shirt in place of a sandbag. 5 shots later, I have the satisfaction of knowing the job has been well done:

5 shot group with my tuned B3-3
5 shot group with my tuned B3-3

Shooting with a 5 MOA red dot, the groups really can’t get better than that. 5 MOA works out to .5236″ at 10 yards. This rifle really needs a scope to bring out its true potential, especially if small game is going to be hunted out to 25 yards.

In the mean time, the red dot is great for plinking. My plan is add a 4×32 AO scope. I’m hoping to have groupings as small or smaller at 25 yards with optics.

I’ve got the ballistics figured out for my 5 to 25 yard workload I plan to use the airgun for:

External ballistic calculations
External ballistic calculations

Squirrel season is coming up on May 28th! I can’t wait to put this airgun through its paces!

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How to tune airgun triggers

In this post, I’m going to show you how I tune my airgun triggers. Trigger tuning can be dangerous if it is not done carefully, so I discourage anyone from doing such an activity without proper tools and knowledge. Trigger tuning will most likely void your warranty. Today, I am going to perform a tune on my Umarex Fuel trigger. It is a decent trigger, but there is a bit of a gritty feel to it.

The first thing I do is remove the action from the stock. I place it on a surface where I’m not going to lose any components. Taking pictures along the way can help you figure out how to put everything back together.

Stock removed from action
Stock removed from action

Take careful note of where springs are located. Many times springs are under tension, so when you remove the pins, things can fly. I recommend placing your hand around the trigger assembly to prevent things from getting lost. Start with the lowest pin and work your way up. As components are removed, place them and their pins in order to keep track of where they go and how they are oriented. When you have finished disassembly, take another picture, it may help you later.

Components laid out in proper orientation for easy reassembly
Components laid out in proper orientation for easy reassembly

Now that your components are laid out, note the mating surfaces. Also note any surfaces which my have a spring sliding along them. These are the surfaces that will need to be smoothed out and polished. Here’s the surfaces I smoothed and polished in my Umarex Fuel:

Surfaces to be detailed are highlighted in red
Surfaces to be detailed are highlighted in red, be sure to click the picture for greater detail

Keep in mind, all I am trying to accomplish is to remove any machine or casting marks, and then polish to a near mirror finish. I want my airgun to be safe and reliable, so I take care not to remove too much material, or change any angles. Here’s what I mean by marks:

Note how rough this surface is. This leads to a rough trigger pull.
Note how rough this surface is. This leads to a rough trigger pull.

I use a couple of sharpening stones to take out the really rough stuff, starting with a medium stone, and finishing with a fine stone. Take your time, taking care to only smooth the surface and not grind it down or change its shape.

Use a sharpening stone to smooth out rough surfaces
Use a sharpening stone to smooth out rough surfaces

Notice that I did nothing to the safety. Next, use a Dremel with a polishing kit to bring the surface to a mirror-like finish.

A Dremel and polishing kit is used to perfect each surface
A Dremel and polishing kit is used to perfect each surface

Be sure you clean any trace of polishing compound from the components. All mating surfaces need to be lightly greased during reassembly. I used silicone grease. This time, start from the bottom up, finishing with the trigger. Refer to your photos to ensure proper placement of parts. Before placing the action in the stock, it is a good idea to inspect for rust and give a good cleaning.

If everything was done correctly, your trigger should be smoother and lighter. Now you have a good excuse to spend more time shooting, as it might take you a few shots to get used to the way your tuned trigger breaks.

For a little more discussion on the topic, check out my YouTube video on the subject:

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Adventures in shimming

7% gain in speed and a 14% increase in energy for under $2.

In my last post, I gained 25 fps with 7.9 grain pellets in my Umarex Fuel by simply replacing the breech seal. I left off with the idea that a shim under the seal might boost my speed a bit more. Today, I’ll share my shimming results.

I started by measuring the original shim:

Thickness of factory shim
Thickness of factory shim

To make my own shim, I started with a 9.5 mm ID washer. I centered it on a bolt and held it in place with a nut. The bolt was then chucked into a drill, and I held the washer up to a bench grinder to wear away the edge down to 14 mm.

From a washer to a shim
From a washer to a shim

The shim was then removed and the burr cleaned up with the grinder. The next step was to carefully reduce the thickness of the washer from 55 thousandths down to 20 thousandths. I used 220 grit sandpaper for this. I simply rubbed the shim in a circular fashion against the paper, occasionally rotating to keep the removal uniform. I checked often for thickness, until I reached my goal:

Final thickness of homemade shim
Final thickness of homemade shim

Now for the final result. With 7.9 grain pellets, I now get a maximum of 960 fps. The 10.5 grain pellets topped out at 805 fps. This means I had an overall increase of 60 fps with 7.9 grain pellets and 55 fps with 10.5 grains. Roughly a 7% gain in speed and a 14% increase in energy for under $2. Based on my experience, I would highly recommend checking the seal protrusion on your spring piston airguns.

Shimming can lead to an additional problem – more pronounced barrel droop. Barrel droop occurs when your barrel points at a slight downward angle from the action. If you are using iron sights attached to the barrel, there will be no problems. If you are using a scope mounted to the action, you will probably be shooting a bit lower, and on some airguns, can even run out of adjustment on your scope. In a future post, I’ll share how I work around this problem.

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Squeezing more out of my Umarex Fuel

When was the last time you checked your breech seal? Breech seals get worn out over time and sometimes don’t even come installed in an optimal fashion. If you shoot a spring piston airgun, you will find this information to be very useful.

My Umarex Fuel seemed to shoot rather slow for a new airgun, 900 fps with regular pellets (7.9 gr.) and 750 with heavy pellets (10.5 gr.). Not much better than ten year old Gamo Shadow. I could just barely feel any protrusion of the breech seal, so I decided to try a new seal.

I found a replacement o-ring (14mm OD x 9mm ID) at a hardware store. Here’s the thickness of the old o-ring:

Old breech seal
Old breech seal

Let’s take a look at the new one:

New breech seal
New breech seal

The new seal is .18mm thicker, enough to feel a difference when it is installed. I decided to chronograph my airgun to see if this made any difference. Regular pellets now shoot 925 fps, and the heavies shoot at 800 fps. Not a bad increase.

I’m convinced that this airgun can do even better. I took my caliper and measured the seal protrusion:

Seal protrusion
Seal protrusion

Only 5 thousandths of an inch, it should be at least 15 thousandths for optimum power. The next step will be to construct a shim to bring this up a bit more. That will have to wait for another time, but I’ll take you all along when I get the time to tackle this project.

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DIY Swinging Pellet Target

Well, this isn’t a homemade airgun, but it is a homemade target that cost under $5 to build and is a blast to shoot:

DIY Swinging Target
DIY Swinging Target

The frame is made from 3/16″ steel rod. It stands 10″ tall and is 8.5″ wide. The corners were made by heating the rod to red hot and bending. The swinging targets are made from the same size rod, washers, and 1″ steel squares cut from an old lawnmower blade. The thick steel of the lawnmower blade should withstand many shots from .22 and smaller airguns.

Detail of the swingers
Detail of the swingers

Looking at the picture above, you can see how the swingers are put together. I didn’t bother cleaning up the welding other than wire brushing.

I finished it with a couple of coats of black paint. The targets get a shot of red paint to make them stand out. The 1″ square targets are perfect for keeping me in shape for small game hunting.

Here’s a video of the target in action:

 

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