I have a Shepherd 3x18x40 With P-1 Reticle on my .300 WinMag. I really like it. It definitely holds its zero.
Texas Dave: If it will really not hold a zero, send it back to them. I cannot see why they would not repair or replace it, damned if I would eat 600 bucks if the thing never worked.
The optics are OK. Will they compare to a Thousand-Dollar-or-more Swarovski with a 30mm tube? No.
I have looked thru it side-by-side with my buddy's comparable Leupold, and neither of us can see much difference. Could be because the Shepherds are made by Light Optical, in Japan. They manufacture the Nikon scope line, and grind most or all of the lenses for Leupold.
Optical quality seems fine to me, I have heard many folks say it sucks, but I just don't see it. I do not, however claim to be the world biggest scope afficianado...
The biggest plus for it is the ranging circles... they really work. Longest Groundhog kill with it: 475yds. First (and only, so far) deer I killed with it was 808yds. Performed as advertised, baby!
Biggest minus is, you are limited to a narrow window as far a ballistic coefficient and velocity. A .30 cal, 200gr Partition @ 2900fps matches up almost exactly. Pretty much dead nuts out to 1000 yds.
The load I use to shoot groundhogs (and that unlucky deer) is a 180 Nosler Ballistic Tip @ 3000fps. This load shoots somewhat flatter than the P-1 reticle. The 1000 yd circle is actually good for 1103 yds.(when zeroed @ 100)
I have done the math, and put a value on the top, middle, and bottom of each circle, to give me more aiming points, and take max advantage of the bullet drop compensation feature.
So, (with this particular load) I have aiming points at:
100, 222, 333, 443, 500, 556, 602, 619, 661, 696, 735, 765, 793, 853, 876, 898, 965, 983, 1005, 1085, 1103, and 1120 yards... after that, I have about 22 minutes of additional elevation I could click in... which would get me out to about 1400 yards.
If I can figure out how to upload a pic, I will post a picture of my cheat sheet.
But the 180 and 200 grain Partitions will line right up (give or take a couple yards either way) on even hundreds of yards, out to 1000.
For your Weatherby Mag, you would need their flatter reticle, designed for the Big Wbys, and STWs, etc.
Definitely chrono your stuff, and do some figuring before you buy one.
Hope this helps.
marc