Since 80% of service rifle is the marksmanship factor I'm willing to settle for any load that can yield sub moa groups.
You can get away with a lot for the 200, 300 line loads and still clean the target.
However, you are going to want your best for the 600 yard line. The 223 isn't an easy cartridge to shoot at Mid Range or Long Range to begin with, so sloppy ammo won't make you happy at the 600 yard line.
Unless you know your exact charge, you don't want to pre load the ammo anyway.
If the gun is happy then load away, but if the gun wants to have a little more or a little less based on the weather changes, you will be better off waiting. It is very common to need to change the charge for the temp changes during the swing from winter to summer. A load that works well at 600 yards in 50 to 75F weather, may tip over in 100F weather for example.
Eventually, you have to plan ahead to travel to matches large enough to earn your "hard leg points". That is where you will have no choice but to load well ahead of out of state matches. Just load them long and seat them when you know you will use them.
If you have any info, could you share how much of a difference, if any, cold weld makes to the accuracy of a round
Like I said before, it is a very lengthy discussion.
The short version is that this can and does happen. When this happens, your SD/ES goes to hell in a handbasket. Your 600 yard ammo will not hold the 10 ring and many times won't even hold an 8 ring. When your 600 ammo SD/ES goes out of control it is game over for your chances at points.
To finish at the top of an EIC match, your goal for 600 yard ammo is to hold inside the X ring for 20 shot strings from a rest. You need the margin when shooting from sling and for the wind calls. If some of the bullets stick in the necks, it is the equivalent of having your seating forces go from like 60 lbs to like 260 lbs. It will typically be a statistical fraction of the batch, not all of them.
Generating the bullet adhesion issue in the labs is one thing. The statistical failures of hobbyist match ammo is another. This problem is difficult to predict in terms of time or effect. The best advice is "don't go there".
This problem can be brought on by chemical reactions between the bullet and the necks, and that can be made better or worse by over-cleaning to bare nascent metal. Folks have tried to mitigate this in many ways including dry-lube coatings on their bullets or added to their prep process. Others experiment with adding preservatives in their tumble media to "treat" their brass. It can be a lengthy topic.
You can go down a very deep rabbit hole, but I am trying to do you a favor that will bypass all of that R&D by either keeping the ammo freshly loaded or seating it long and finishing it at the match. YMMV
