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!