With 53 gr. of RL-15 I don't see the need for dacron filler which is typically used to hold a much smaller powder charge back against the primer to avoid a situation known as detonation. But if it works for you there's no harm so carry on.
Dacron keeps base obturation minimized and maintains bore condition; it works like a gas check. Doubly so with a gas checked bullet, pressures close to max at jacketed bullet velocity. It may not be needed in a conventional manner, but a 35 cal, 250 gr. caster begins to foul towards the muzzle when leaned on. Dacron can be a fix for this.
If you can fire rounds all afternoon on a hot summer day with groups around an inch without resting the gun, and it requires a little less 15 and a touch of dacron, you do it!
I have three guns that are "dialed in" with just a bullet and a max load for jacketed bullets except they use cast bullets. They are exceptions. The rest need coddled somewhat to do the impossible.....
