I really really doubt you need a small base die. Take a fired case and compare it to a sized case from your die setup. If the bump is only .0015-.002 totally possible you’ll experience hard bolt when commanding battery. Try increasing bump in increments of 1/1000” until brass no longer binds when closing bolt. Check this with just case, no seated projectile. This is the most likely cure but there are other considerations to check. Trim length vs your chamber. Also what is the O.D. of a fired neck vs a sized case (neck)? Alpha runs about .0135” neck wall thickness so there shouldn’t be an issue.
I find the Alpha LRP to be extremely consistent brass. Can’t compare to Lapua in 6.5cm, but I use blue box exclusively for my 6Dasher and it’s moa and SD/ES are all the proof I need. Only real assessment I did before loading was weighed some cases and checked col and neck od. All very uniform tolerances out of the box. I found that the Alpha case capacity in H2O is on average about 2gr less than the brass I was using- Hornady. Caution, start low and Work up. I quickly found my 6.5cm node w just 39.3gr H4350. Ran my first seating test and will reshoot just on either side of .041”OTL to verify. 140 eldm- x3 @ 100yds .138”moa So far so good. Hoping to tighten up after 2nd firing. Ps Alpha primer pockets were tight, more than usual seating force required. (Fed210)