This is a key point for loading match ammo in my mind. I only shoot Swiss powder at this time in match ammo. I shoot other powders for other applications. Accuracy and lack of fouling with Swiss is the reason. I have found that basically no compression and a mild primer can produce a good accurate load with the most manageable fouling. As an example, yesterday was out local BPCR silhouette day. Weather was a mild fall day and we shot under the sky with our barrels in the sun. It got into the low 70's F with light winds blowing harder by match end.
Silhouette target distance in meters - for yards add about 10%
Chickens 200 m (219-y)
Pigs 300 m
Turkeys 385 m
Rams 500 m
I shot the whole 40 shot match starting with pigs without wiping. With sighters, this match was a total of 58 shots, all using a few breaths on the blow tube between each shot. Accuracy never varies. After 14 or 15 shots at one stage the rifle sits for maybe an hour and then up to the line again. With a few breaths to start off, you are good to shoot the next stage with accuracy.
Due to my own error I missed one target each on Pigs, then Turkeys and Rams for a score (9-9-9) 27 going into the offhand stage Chickens. Accuracy is so good you and your spotter can move the group around on the target.
At the end of the match I checked the barrel for hard fouling by putting 5-6 long easy breaths into the barrel with the blow tube and then wiping with a dry cotton patch. The barrel sounds squeaky when do this.
For me, this level of performance does not happen with a compressed load and for sure not with Graf, KIK, Schuetzen nor the current ( last 15-20 years) GOEX and though I am hopeful, has not come together with Olde Eynsford. However, with my remaining FFg OE, I hope to give it a better look.
Compression, or lack of it, powder choice and primer choice are the three big deals as far as I am concerned.
So, rather than compress the powder with the wad, I place the wad about 1/8" into the mouth of the case and seat the bullet pushing the wad down to the top of the powder charge.
Load density; If that case is 98% full under the bullet, 100%, or 102%, it maters not. Just find the accuracy spot.
I very much agree; "Finding the right compression makes a big diffrence in fouling and accuracy." and I would add powder choice too.