I know of other people with Tikka's that had headspace issues. Not quite the same issue as your's but speaks for their fit and finish. They are not all bad, you got the 1:10000. I would buy one.
My first set of 300 WSM dies were Hornady. After several tries and working with Hornady on the phone, I sent them back to Midway. Check the case length (not head space) after sizing.
I usually FL size my new brass then trim it. But that's just me.
Before you call or send the rifle back, you have to fire factory rounds. I've sent a rifle back and the first thing the company told me was which brand of ammunition did to use. Do not say reloads or hand loads, they'll dismiss you as not knowing what you are doing. When in actuality your hand loads will in fact be more accurate. Go with a quality brand. I used Black Hills Gold Match grade 30-06 rounds (the rifle I sent back was a not a Tikka 30-06) and they still said there was nothing wrong with my rifle. After convincing them there was a 30 degree temperature difference between their range and mine, they replaced the stock. Again, not the same problem as what you are having.
Hope I helped
HaYen
