I know for a fact that both of the scopes that Art named can lose their zero. My brother's Leupold on his Ruger .270 went "off" on a deer hunt 4 years ago. He "rolls his own" ammo and had his setup tuned just how he wanted it. Somehow, between the time he checked zero at camp the day before and the time the buck followed a doe across in front of him about 10:30 the next morning (the rifle had spent the intervening time cased and laying on the back seat of his Bronco) the point of impact was about 12 m.o.a. high and left and of where he thought he was aiming. He never had another chance at a buck during that hunt after rezeroing back at camp. Accessible iron sights could have salvaged that hunt for him.
The Simmons I HAD on my synthetic stocked Savage 110 .270 started acting up late last summer, it absolutely would not hold a zero from one range session to the next (kept in a hard case only transported on a couple of 12 mile roundtrips) then the top crosshair broke when I shot it again. The recoil from hot handloads (they really are only what factory loads USED TO BE but no longer are) in that rifle just shook it apart. I don't have iron sights on my Savage at all so if this had happened on a hunt I would have been s.o.l. Yes, Simmons scopes have lifetime garauntees, but that wouldn't helped if the reticle had broke in the field rather than at the range. This happened about 4 weeks before season opened. I sent the scope back to Simmons, and they told me it would be about 2 weeks, I worried about delays so I went out and bought a different scope. They repaired it at no cost (besides $7.00 s&h) and did get it back in 2 weeks but I no longer have faith in it and it now lays in one of my junk drawers, maybe I'll put it on my new Rem. .22 I got for Christmas, but I won't ever put it back on my Savage.
p.s. I have been thinkin hard about fitting sights on my Savage and getting quick detach mounts for my scope. With a good scope in good mounts problems really are rare, but a backup plan never hurts.
[This message has been edited by bergie (edited December 28, 1999).]