Wow, at only 500 fps I would have expected a busted spring for sure. I've been there before with a CFX, had one that liked to eat springs every couple thousand pellets. Fixed that by installing a Theoben gas ram. I'll answer your questions first, then make more comments :-).
1. Yes and yes.
2. Not typical but not unheard of, either.
3. Your assumption is correct.
4. Small needle files, a Dremel tool with grinding and polishing points, and various grades of wet/dry sandpaper, both freehand and with a custom made pilot for the compression chamber.
Like I said, I've been there, twice. First, when the factory spring broke after less than 2000 pellets. Second time was post tune with a Maccarri spring, the second one partially collapsed after less than 1500 pellets. Then, to add insult to injury, it developed a sealing problem with the rotary breech oring. It took awhile, but I finally got it sorted out, and came up with a couple of techniques that are specific to the CFX. And as previously mentioned, I replaced the spring with a gas ram, well before PA was offering the Air Venturi units.
Most of the basics of tuning a springer have been covered very well elsewhere, but there is one item specific to the CFX that needs a little extra attention, and that's the rotary breech. When I honed my compression chamber, I mostly followed standard practice, but I took it to 400 grit instead of the more typical 320. Once that was done, I made up a special paper holder that was just slightly longer than the rotary, and polished just the end of the chamber where the rotary rides to 1500 grit. That was the finest I could find locally, I'd have gone 2000 if I could have found it. My theory was that an oring seal works best and lasts longest with the finest polish you can get, while the piston seal needs a little "tooth" to work best, just like the rings in a car engine. Don't know if I was right, but I do know that that rifle ended up incredibly consistent right at 15 fpe, and was a dream to shoot. I gave that rifle to my little bro a couple of years ago, who then sold it to a friend. I'm hoping I can talk that friend into trading it back to me for a Diana 48 I got recently. Need I say more about my opinion of that CFX ;-)?
If you're going to tune it yourself, order the parts from Maccarri. I'd recommend a spring and piston seal, and here's another place I'm going to fly counter to common practice. DON'T order the E 3650 or Tarantula that most recommend. The 3650 is too long and skinny IMO, and likely to kink. The Tarantula is just too heavy, it might net a little more power but it makes the gun harsh, again IMO. However, if you do decide to use the Tarantula, get the Tesla seal. It's a little bigger and stiffer, and might help tame the Tarantula a bit. Otherwise, I'd suggest the Ultra XLD and the standard Apex piston seal. That combo, with a good deburr and lube, should net you a very smooth, comfortable shooter that will still put the right pellet down range in the 850-900 fps range. BTW, the Ultra XLD spring fits the factory guide almost like it was made for it. If you have the ability to make a new guide, great, but if not, that spring and the stock guide works great. Worst case, you might need to shrink wrap the guide. And while you're at it, get a set of JM's "Old school buttons" and button the piston. That's about the only thing I didn't do to my CFX, and if I get it back, it will be the first thing I do. Later.
Dave
