Catch-22

I'd check all the usual suspects; 1.Scope ring screws locking down the scope 2. Rings to base/rail screws 3. Rail to action screws 4. Action to chassis screws, front and rear 5. If using a moddy or muzzle brake, check how well it's locked down. Or try without it on. if none of the above resolves the issue, check rifle with a different scope and set of rings to rule this out. Failing that, try some factory ammo to check there's nothing wrong with the home loads. If all else fails, get it checked by a rifle smith.

TBH, I wouldn't have thought RS62 to be well suited to the lighter bullets anyway. It's a slow-ish burning powder which, in my experience of other similar slow burning powders, is best suited to the heavier bullets. The slow burners need more dwell time in the barrel to generate sufficient pressure and thus velocity to push the bullet out. The heavier the bullet (more mass to force out the barrel) the greater pressure required to do so. So a light bullet will exit before peak pressures have been reached, reducing the effectiveness and purpose of the slow burners. On the flip side, a faster burning powder like RS50/RS52 or N140 might be too fast to push the heavies along. In my own tests of 140g bullets and N140 in my 6.5x47 velocity was down but pressure was high. Really I needed a slower burning powder. Useful test none the less, lets you know where you stand visavie your components. I am surprised in only reaching 2900fps with 46g, that's about 10gns more RS62 compared to N140 to push the 123g Scenar at similar speeds from same barrel length (albeit a 6.5x47, not 6.5 Creedmoor). If you're keen on the 123g, try RS50 or RS52.

I came across this method of keeping track of one's shots and it seems very simple and completely logical to me. I'm definitely going to give it a try but I'd be keen to know if anyone else has used it? https://www.autotrickler.com/blog/how-to-improve-your-score-through-strategy

No I don't have plenty of experience of stalking with .223 but I know a few people who have and all preferred the switch to a 6mm or above. They reflect what I said, a larger bore diameter, with the ability to drive faster, gave greater flexibility and reduced chance of a wounded deer. one good reasource is Nathan Foster. He's shot litterally tens of thousands of game (goats, pigs, deer etc) and is very knowledgeable on the subject. Not much in the way of .223 resource as he too feels it's a bit unforgiving unless neck shooting, but there's plenty within the wider .224" knowledge base. Simply follow the link, select Knowledge base, Cartridge Research, check .224" and pick from the list of cartridges. https://www.ballisticstudies.com/Knowledgebase.html

I think the main issue with Gamekings in general are that they have quite a stout jacket. In some calibres, they can pinhole like a FMJ. To be safe, I'd avoid the meat saver shot (behind foreleg into the lungs) and ideally either neck shoot or alternatively drive it directly into the shoulder/foreleg to help aid expansion & grounding of the animal. However, leg shots may not be the best option if the animal is largeish (90kg+). If not driven fast, you may get shallow penetration. Personally, and no offence meant, but I think the .224" calibre (in its .222/.223rem for) to be a bit lightweight for deer. The light bullets & small wound channels leaves no margin for error. Anyhoo - it's legal, so aim straight & good luck!

Ordered mine today, can't wait for it to arrive. Superb comms by Lubo too - top bloke!