Gentlemen,

I have an old English-made Mauser fitted with a Williams peep-sight. I don't shoot the rifle that often, but when at the shooting range a week ago, I discovered that the rifle's zero had shifted. This all with the same load I've been using for ages.

All the screws were still tight, so my only assumption is that the peep-sight is somehow shifting its zero. I assume its made from aluminium, and whether this will have any influence over the matter I don't know.

Has anyone else had any experience with the Williams peep-sight in the past? Either positive or negative?

It may not be the sight. Rifles shift zero for other reasons, too.

There are 2 Williams peeps, one has clicks and the other doesn't. The non-click 5D has clamp-screw adjustments that can be accidentally moved by a bump against a hard object but the more precise Foolproof with the clicks is more likely to stay in adjustment.

IF SET & LOCKED PROPERLY AFTER SIGHT-IN!

The Williams Foolproof design is IMO far, far superior to any other peep sight I've ever seen for field shooting. Its locking set screws on the adjustment staffs are, literally, foolproof once they're set and locked in. OTOH the Lymans and Redfields, when used in the field, have a regrettable tendency toward unintended RE-adjustment by curious uninformed fingers or sliding in and out of the soft case or saddle scabbard.

The alloy Williams is no more likely to shift dimensions or positions from temperature than the steel Lyman or Redfield. But the non-click Williams 5D version is not one I'd choose for my primary sight; the more precise Foolproof is far, far superior and IMO is absolutely
THE best for rough use if you don't mind alloy.
Regards, Joe