Good morning RD Skidmore. I'll not beat about the bush............. I have been an Armourer since I started my apprenticeship in January 1963. When I say 'Armourer' I don't mean an enthusiastic amateur or one who has tinkered with a few No4's and the like, but I mean a REAL Armourer who's been there,and done that - you know the spiel......... I am also a graduate engineer so from that, you can take it that when I tell you something about a No4 rifle, having spent my formative years, on the bench, fixing literally - and I mean it - hundreds and hundreds, probably thousands of them, day in and day out AND range testing, accuracy testing and zeroing huge piles of them, you and the rest of this forum can take it that when I tell you about sights and zeroing, then it's the real McCoy.
Now come closer and listen as I don't want everyone to hear........... The issue tool to adjust the foresight, regardless of whether it has got a reverse headed keeper screw or not, is a complete waste of rations. Say that after me slowly..... 'A COMPLETE WASTE OF RATIONS' Good.
It was taught during your apprenticeship, together with the variations per turn by rote. But once you got out into the real world, it was left back in the workshop cupboard along with the other theoretical crap, while you learned from the more experienced Armourers, who had served from Monte Cassino to Korea how things were REALLY done.
There IS a place for the forked/reverse headed screwdriver and foresight cramp. You could give it to someone you don't like as a fishing weight or you could slip it into your range bag so that you will look like a bit of a wally (you know the saying, all the gear and no idea) if anyone peeks in.
Real Armourers as opposed to the all the gear and no idea queens just know that on a No4 rifle it's 'FORESIGHT INTO THE ERROR' So if your shots are sneaking over to the left at, say 100 yards, just a slight tweak of the foresight blade to the left with a brass drift and small hammer through the foresight protector will do the job. Oh yes, I almost forgot. A real Armourer will just KNOW from years and years of experience exactly hyow much to move the foresight over too.
There, that wasn't toooooo difficult was it. Now just a little decorum from now on and you'll be welcome. But, it's not wise to tell the most senior Armourer in the Army that what he's written about sights and zeroing and what you've read is drivel.
Thunderbox and that Peter Laidlerbloke, you can both now rest assured that you're dead right