I'll agree with fox here, from a newly deep cleaned barrel my first group in most my rifles is usually 3/4 to 1 moa (in a different location) , the next group is 1/2 moa, then they pretty much all touch after 10 shots have fouled the barrel(100 yards) a couple months ago i shot a 5 shot 2.85" group at 600 yards with my 243 that hadnt been cleaned in over 250 rounds... my best 600 yard group to date

but i think you may be able to duplicate if you cleaned your barrel every single shot, and always kept it consistant.

Obviously there are exceptions to every rule, but for most cases a fouled factory barrel will shoot better than a clean one (usually)