Gamo Shadow Teardown and Tune

After tuning the trigger, I decided to tune the action of my Shadow. This was my first magnum springer and I abused it by using both light pellets and adding various combustibles to the chamber. It is now 12 years old and shooting surprisingly strong and consistent. Hard to believe that with the way the spring came out this morning:

Spring had been broken for years
Spring had been broken for years

Don’t spray ether in your compression chamber! I knew better, but it was so much fun at the time. It’s kind of cool seeing and hearing a pellet exit the muzzle at 1600+ fps. The piston seal didn’t have any gouges or burns in spite of all this. The broken end was tangled with the end of the remaining spring and held in place with the tophat.

I’ve gone ahead and ordered a new aftermarket piston seal and spring. I wanted to be able to shoot in the meantime, so I decided to try a spare Chinese B3 spring. The tophat and guide were a much tighter fit than they were with the stock spring. There was a tad more wiggle room between this spring and the piston, but not so much that a bit of heavy grease couldn’t fix.

Getting things ready for installation
Getting things ready for installation

I decided to add a bit more preload to the spring as well as mass to the piston by adding two hardened washers between the tophat and the plastic spacer inside the piston. I lubed everything lightly with Supertech lithium moly grease and reassembled.

How did the tune go? Prior to the tune, it would shoot RWS Superdomes at 836 fps with lots of twang. Now it shoots them at 818 fps with a solid thud, very gas ram like. Cocking is smooth as butter and the shot cycle is to die for. In spite of the weaker, shorter spring, the Shadow only lost a half foot pound of energy. What it gained in smoothness is hard to put a number on.

It’ll be interesting to see how the more efficient seal and powerful spring I ordered will compare to this current tune job. One thing I have learned through all this is that I favor springs over gas rams. With a proper tune, a spring can match the smoothness of a ram. Apparently a stock spring will long outlast a ram as well.

Check out the before and after:

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Gamo Shadow 1000 Trigger Job

A few years back, I decided to jump on the gas ram bandwagon, purchasing a Umarex Fuel, and leaving my Gamo Shadow 1000 to rot in the gun cabinet. Over time, my Fuel has gotten weak. The breech seal and piston seal are good, so it’s looking like the gas ram is losing its magic sauce. Ordering parts through Umarex isn’t my favorite thing to do, so I decided to pull the Shadow out and dust it off.

Much to my surprise, it shoots extremely fast and consistent in spite of the years of abuse it has endured. Lighter pellets shoot in the 920 range and heavy pellets shoot in the 710 range. The Shadow is so light compared to my Fuel, making it better for carrying around in the woods. On the downside, it is very twangy and the trigger pull is really bad. If I can fix that trigger, I’ll give it a good tune and turn it into my go to magnum springer.

The Shadow comes with a short trigger adjustment screw. I rummaged around my spare parts and came across a longer screw with matching threads:

Stock screw on left. The longer screw should give me more adjustment.
Stock screw on left. The longer screw should give me more adjustment.

Note the pin riding in the slot above the trigger blade. As you squeeze the trigger, that pin engages a lever between the trigger and the sear. If I can bring up the diameter of that pin a tad, I should be able to get rid of virtually all the creep. I used a bit of copper wire bent around the pin to do just that:

Note the copper ring. This eliminates the creep in the trigger.
Note the copper ring. This eliminates the creep in the trigger.

Time to put it all together, adjust the screw, and make sure everything works safely. I recommend taking it outside for testing. I begin by making sure the sear catches. A pellet is then loaded while holding the barrel open to prevent dry firing. The trigger is squeezed with the safety on to make sure it is working order. I then proceed to slap the stock hard several times to make sure it will not accidentally discharge. When you get it all right, you end up with a trigger like this:

The safety works, there is zero creep, and a light squeeze of the trigger fires the gun. I’m very pleased with these results. One thing will make this a perfect single stage trigger: eliminate over travel. I’ll save that one for a later time.

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Daisy 880 Power Valve Mods

Now that I’ve made the pump as efficient as possible, it is time that I turn my attention to the valve. I am going to attempt to add volume in parts of the valve and take away volume in others. In this way, I’ll hopefully add power without adding to the number of pumps.

First, I’m going to modify the metal abutment washer. Here’s what it looks like stock:

Stock metal abutment washer
Stock metal abutment washer

Let’s go ahead and take a peek at the stock daisy 880 valve so these mods will make sense:

Stock Daisy 880 valve internals
Stock Daisy 880 valve internals

As you can tell from the above picture, the top part of the valve holds the greatest volume of air. Keeping this in mind, I ground down only the top of the metal abutment washer. In this way, I am maximizing the valve volume where it will most efficiently flow. Here’s what it looks like when complete:

Modified metal abutment washer
Modified metal abutment washer

I was careful not to remove too much from the pin area. Keep in mind that pin is the only thing holding the washer in place. If it fails while pumping, it’ll shoot forward – potentially hazardous to one’s health!

Next, I’m going to take a needle file and remove some material from the top of the valve body. I went ahead and removed the exhaust valve from the body. Here’s what it looks like prior to modification:

Notice the size of the rectangular port
Notice the size of the rectangular port

I took a needle file and coming from the abutment washer side of things filed the port nearest the valve seat. I filed it at a downward angle, improving the flow as well as adding a bit more volume:

The port is enlarged and angled toward the valve seat
The port is enlarged and angled toward the valve seat

For now, I’m going to leave the transfer port at the stock diameter and see where these mods have gotten me. Here’s another view of the modified valve from a different perspective:

Made a bit more room, adding volume and flow
Made a bit more room, adding volume and flow

I didn’t get a picture of the next thing I did, but it is easy to describe. Once the seal is placed on the abutment washer, I used waxed dental floss to build up the area between the seal and where I ground it down. In the future, I plan to 3d print a piece to take up this dead space.

I then put everything together and took her outside to chrony the results. Using 10.5 grain Crosman domes, I got an average of 661 fps with 10 pumps. I’m now producing 10.2 fpe with 10 pumps, and have as much energy at 25 yards as the stock Daisy 880 made at the muzzle!

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