Open Sights Aiming Question

[No1_49er]

Maybe the OP has found a satisfactory answer to his question(s)??
https://www.milsurps.com/threads/lee-en ... ost-561571

[MG5150]

These sights are calibrated for military MkVII ammunition, firing a 174 grain flat based (and open based) full metal jacket projectile over cordite at 2440fps. As far as I know, no one has ever succeeded in replicating the ballistics of that round using modern powders and projectiles. Modern ammo won't match the elevation settings marked on the sights. There are, however, plenty of accurate loads for the .303, and several reasonable factory loads (eg PPU).
Rather than get caught up in the sights at this point, I'd suggest you get some .303 hunting ammo, either your own handloads, or PPU 150gr or 180gr, and try a few different types to see what suits your rifle. Set the rifle up on a nice firm front rest and fire some 5 shot groups at 50m or so, WITH THE SIGHTS ALL THE WAY TO THE REAR (like in the picture above). Pick the best group, and then zero your rifle to that ammo.
Don't file the rear sight down. If you get it wrong, replacements are expensive. Do the adjustments on the foresight only, as per Blade's post above.
Once you've zeroed at 50m, set some targets up at other ranges (maybe 100m and 150m) and see where the shots land. I doubt you'll see much difference in elevation from 50m to 150m.

As I plan to shoot deer at 50m-150m I'm best to just leave the sights as is?

I'll likly go with the PPU 150g but I guess buying a pack of 180g and seeing which it prefers makes sense.

You mentioned seeing how it goes at 50m to find the best ammo, then zeroing - I'm not understanding whether I am zeroing it for a specific distance or just leaving it at the current settings as 200m if further than I think I'd use it for and definitly won't be hunting deer at 400+

[bladeracer]

Put some groups on paper first so you actually know where it's zeroed.
Four to five inches high at 40m puts it somewhere between 300m and 400m is my guess, which will be something like 400mm to 500mm high at 200m, depending on the ammo you use.

If you're not going to reload, try some ammo and see if it it'll group. If it's accurate then you can determine where it's shooting and whether you want to adjust the sight.

If you have good eyesight you can shoot groups at 100m. I find 50m is about the furthest I can see a small aiming mark (not a 44 gallon drum) reliably with open sights, so I do initial load testing at 50m.

As I plan to shoot deer at 50m-150m I'm best to just leave the sights as is?

I'll likly go with the PPU 150g but I guess buying a pack of 180g and seeing which it prefers makes sense.

You mentioned seeing how it goes at 50m to find the best ammo, then zeroing - I'm not understanding whether I am zeroing it for a specific distance or just leaving it at the current settings as 200m if further than I think I'd use it for and definitly won't be hunting deer at 400+