I've tried two subsonic loads in my sportster, the cci cb short shot horrible. 3 to 4 inch groups at 20 yards. Very quiet, a little pop, 727 fps, but couldn't hit anything beyond 10 yards... The other subsonic I tried was remingtons "high velocity" 1095 fps. They were a wee bit louder than the cb's but were 1 holers at 20 yards. I've gone out and shot them three times and all three times were ragged holes. The last time was shooting apples, walnuts, acorns, etc. Extremely accurate, I couldn't, and still can't, believe how good they shot.
But, like I mentioned, they're a little bit louder than the cb's, but still not the crack of a LR.
Hope this helps!
Oh, if you ask sportsmans they can probably order you a sportster 22lr, should be around $103-$110 I would guess. Then you can send it away, spend $63 for the 17hmr varmint barrel, and have the 22 for quiet work, small game, and cheap plinking, and have the 17hmr for crows and stuff, all for around $170 + shipping to nef.
later,
scruffy