What is more accurate a barrel that is CLEAN or DIRTY?

This is a debate for the ages. Some swear by cleaning their rifle constantly while others wouldn't think of ever cleaning their rifle for fear they might lose the accuracy they cherish. So which is it? What is more accurate, a barrel that is dirty or clean?

This last time out to the range my objective was to test a series of ten loads I developed to determine which would shoot the best groups. Having thoroughly cleaned my barrel after the last outing I knew I was starting out with a squeaky clean barrel. My concern was that having a clean barrel to start with would produce better groups with the first few loads and then they would gradually get worse as the barrel fouled.  I resolved to do a good cleaning between each 3 shot group to eliminate any inconsistency. WHAT A ROOKIE MISTAKE and it showed.  My groups weren't impressive and once again I came away very disgusted that I wasn't getting the sub moa accuracy I expected.  At first I blamed it one using a my bipod on a less than perfect shooting bench rather than sand bags and resolved to buy my own set of bags immediately.

What I learned:
After sharing my dilemma with Ryan from "The Road to Precision" series on youtube I learned a valuable lesson that I'd like to share. If you have watched Ryan's series you know that he is extremely scientific in his approach and even encroaches on being a little OCD at times so I trust that before he says anything it has been tried and tested to the extreme. What he shared was surprising and gives me hope that my groups will be better the next time around.


Here is what Ryan had to say about FOULING FOR ACCURACY: 

Your first shot through a clean barrel is always a fouling shot and should never be counted in the group. That said, it it also wise to track where that shot tends to land, because first shot placement will always be off a little from the main group. If you are hunting with the rifle and don't have time to foul the barrel before that big moose shows up, you are going to want to know where that first shot will place from a clean barrel. 

when I first started into shooting, I was religeous about cleaning every 10-20 shots. Then I read an article about cleaning frequency VS. precision. Simple put, only custom rifles in the extreme Bench rest competitions need to be cleaned between groups, everyone else WILL BENEFIT from a dirty barrel. 

So I put the theory to the test. I shot alot of groups and didn't clean at all for 200 rounds. I should have documented my results, because it showed what most others are finding. 

From round 1 until about 20, the groups were on the larger side. As I passed the 20 mark the groups started to shrink. I found the best groups happened between 50 and 75ish rounds. as I worked my way to 100 and beyond, the groups started to open up again. 

Becasue of this, I never clean until I have at least 100 rounds down the tube. And I try to make sure I have at least 10 rounds through the barrel before I go to a competition, because a standard competition uses about 65 rounds total, and I want to see good precision on the 900 meter line. 

There are also some really good articles out there on the net, written by Gale Mcmillan. Its really hard to argue with someone who has changed the firearms industry. 

The one I specifically like, he bashes the barrel break-in routine. Calls it a big waste of time and bullets. Also has proof that a fellow gun smith started it as a rumor to help increase barrel sales. The rumor stuck and now everyone belives it as LAW. Funny stuff coming from a master rifle builder.

Here's a video from the Best of the West Series on the Same Topic

Interview with John Krieger, custom barrel maker and legend. Talks about cleaning & break in at 4:00 into video.