Peter makes a good point about the ultimate "robustness" of such arrangements on the L1A1. Probably not "soldier-proof" enough for some folk who are sometimes more than a little casual about equipment that others paid for.
The mounting system on the H&K rifles is quite robust, if a little bulky, and designed into the system, pretty much from the beginning. It holds zero after multiple mounts and dismounts and prodigious quantities of rounds downrange. You are advised to maintain the rubber boot on the rear of the scope to avoid engraving an extra "eyebrow" during shooting. I copped it once whilst hunting pigs in the Channel Country in Queensland. The action was rather chaotic on one occasion: the porkers were running towards me, very close and fast. I dropped my head height to use the iron sights THROUGH the scope mount. Only ever did that once! More fond? memories of "the good old days".
I never found a mount for the SiG AMT in Oz, probably couldn't have afforded one, anyway.
A friend had a couple of the late-pattern AR-10 rifles with the specially slotted carrying handle and the correct optics. They were quite nice to shoot and the mounts held zero very well.
Another thing I discovered was that the SKS was absolutely brutal on scopes. "Cheap" entry-level Tascos and "Brand-X" jobs would pop their reticules after a distressingly small number of ball rounds. Quality scope brands, (worth three or four times the price of the rifle), held up well, as one would hope.
Another variation on the theme was a bunch of small "reflex" sights I saw on L1A1 dust covers, back in the 1980's. I didn't grab one at the time. Anyone remember them?