Short question. Yesterday, we tested a new .30Nosler rifle at the range, at 100m, 200m and 300m. Approx. 15 bullets were run trought the barrel at this time. First groups were excellent, 1/2 MOA at 300m. But after 15 rounds this ended. Groups were over 3MOA at 300m...... Load was a 168grs Ballistic Tip @ ~3200fps.
30 bullets, to much for this round without extra cleaning?

I suspect your breaking in the barrel and in such a manner as not prescribed by many. After a couple of hundred rounds thru the bore it will probably be fine. Most any gun will shoot better after a couple of hundred rounds. Some like yours shoot good right out of the box others not which is usually a clue it will be a shooter when broke in....Its a crap shoot anyway you cut it, fortunately it usually works out fine.

Also sounds like the bore was not lapped smooth the factory.

quote:

30 bullets, to much for this round without extra cleaning?

I have a 243 that after 30 plus it goes to crap.

Shoots like a lazer before that and after cleaning. I just make sure I clean it at around 30 shots