I posted this a year ago on the main page, but thought this new forum would be a great place to archive this.

Roald Van Antwerpen had a sharp eye in spotting this rifle for me at the 2010 AR Airgun Show. I've been looking for a .177 cal Sharp UDII to complement the .20 cal UDII I've had for years. Chances of finding these rifles today are a long-shot. And, my trip to AZ to help Greg D in his shop for a week posed a scheduling conflict with the AR show. So I was shocked to receive Roald's call, "You'll never guess what I have in my hands." Thanks again, Roald.

The previous owner said the rifle wouldn't hold a charge, and indeed it wouldn't. Having another Sharp to compare it with was so helpful in identifying the problem. So after replacing the valve o-ring with another -- of the proper size -- it no longer leaks. In this shootable condition, it shot about 650 fps with 10.7 gr Kodiaks, using .45 gram of CO2 per shot.

I then torn the rifle down and installed a new, high flow delrin valve stem, along with a larger volume, poly transfer port. A bulk fill adapter I made earlier for my 20 cal Sharp replaced the standard 12 gram, two-cart charging system, yielding a new capacity of 52 grams of CO2. A Tasco AG2-7x32 scope matches the optics on my 20 cal Sharp.

Last Summer I made two anodized LDCs for my 20 Cal, one of 1" OD and the other of 1 1/8" OD. The larger one lives on the 20 Cal, which left the 1" wanting for a home, which it has now found. The smaller capacity of the 1" LDC is a perfect balance for the smaller caliber. The only sound you hear is the hammer strike on the valve stem.

All these mods are easily reversible, so I can return this rifle to stock condition in the future.

Before and after Pictures



I'm very pleased with the initial, 10% improvement in performance. I'm especially happy that the mods have not cost too much in shot count... only .71 gram per shot, now. This means I can still get more than 100 shots per fill. I might make a higher capacity valve body in the future in a search for 15-16fpe (as with the 20 Cal), but this will use a good deal more CO2 per shot. So I'm happy with a full 12fpe for now.



Aside from the accuracy, what I like most about these Sharp rifles is their performance to weight ratio. With all accessories installed, it barely touches 3000 grams (6.5 pounds), making it a very handy rifle to carry in the woods. No need for sling swivels for these little jewels.

And finally, my 20 Cal Sharp (below) now has a stablemate!

is the very thin trigger blade. On both of my UDIIs, I have added broader trigger shoes. I made one of them in aluminum on my lathe. The second is a resin casting of the first. Can you tell which is which?




Posts almost always edited to correct typos/spelling

Here is a picture of the standard valve on a UDII. I assume this is the same for most if not all the CO2 guns.




Posts almost always edited to correct typos/spelling

The GR-75 valve is slightly different in so much as it also has a 'gas charged' plunger which prevents pellets being fed from the magazine if the gun is not charged with gas. This stops any pellets being fed into the barrel unless the gun is capable of discharging them.
I have a GR-75 valve in pieces here that I need to make a new valve stem for, when I can find the spare time to get busy with my lathe.