I’ve done a lot of modifications to my Daisy 880 and tracked what worked vs. what didn’t. The most effective modification is to improve the efficiency of the pumping mechanism. This is super easy and cheap to do, you’ll need a few easy to source things – epoxy putty, dental floss, and teflon tape!
Let’s begin by looking at the pump head:
You’ll notice the depression in the head as well as how the center portion of the head rises above the rest. Both of these things produce headspace, lowering compression. Since this airgun is marketed toward younger shooters, this design is understandable. We, however, are not going to pump this rifle 50x, we just want to squeeze a reasonable amount of extra power out of it.
I turned this piston into a true flathead by using some epoxy putty. The entire end of the piston was covered, and enough to slightly overhang the edges. Once it was cured, I sanded it flat and smooth with fine sandpaper. Here’s the end result:
We just have one more thing to do to the piston. Remove the original o-ring. Apply a couple tight wraps of teflon tape across the o-ring groove. Install a new o-ring and set the piston aside for now.
When the piston is at the full open position, you may notice that there is a lot of space between the o-ring and the bottom of the air intake slot. This represents wasted space that could be put toward pumping. To fix this,we are going to move the pump tube forward a couple hairs.
You’ll notice a depression in the main frame of the 880 that limits the forward motion of the pump tube:
I used a flat needle file to remove a bit of material, allowing the pump tube to be installed forward of its original position:
I was careful to remove the resulting burr to prevent the pump o-ring from chafing during installation. The next thing I did was remove the pump tube o-ring from the outer valve body and give it the teflon tape treatment before replacing with a fresh o-ring. The pump tube was then reinstalled, but not completely bottomed out. I left enough gap to make up for the amount of material removed from the frame.
This is where the waxed dental floss comes in. I wrapped it tightly around the space between the valve body and compression tube:
When the valve is reinstalled into the frame, you should find the valve retention pin doesn’t slip right in like it did before. I lightly tapped the back of the valve with a hammer until the pin snapped in place. This modification takes out slop, leading to better accuracy as well as power.
One final thing – replace the original trigger spring with a heavier wire spring. This will help prevent valve lock and ensure we are dumping air as fast as possible.
So what is the final result? Out of the box, the Daisy 880 shot 10.5 grain pellets at 597 fps on 10 pumps. We are now up to 640 fps. This gave us a gain of 1.24 ft-lbs. We are nearly to 10 fpe with 10 pumps, a very respectable number indeed. At this point, I don’t recommend pumping beyond 15x, even with the upgraded spring, 20 pumps resulted in a hiss and weak shot, indicating that we are approaching valve lock.