I rarely let my rifles go more than 20 or 30 shots without cleaning the barrel. On the odd occasion when I have fired more shots without cleaning, I have never detected any deterioration in accuracy. And, of course at the range you will hear folks talk of never, or rarely, cleaning their centrefire rifles.
That led me to wonder just how many shots you could fire before a loss of accuracy could be measured. Tasco Sales Australia supplied the Fiocchi ammunition I used and I made many a trip to my local SSAA range to test just what happened to accuracy when the barrel was not cleaned.
I used my Weatherby Vanguard HSP in .223 Rem for the testing with the Fiocchi factory ammo. I fired both the 55-grain polymer tipped EPN rounds and the 55-grain soft-points. Both shoot sub-MOA in my rifle but it is the soft-points that perform a smidge more accurately and are what the rifle is zeroed for. At 100 yards, the 55-grain EPN polymer tips shoot about 20mm to the left of the soft-points. All groups were shot on the 100-yard line.
I started with a well-cleaned barrel. I fired three-shot groups and measured the group size as well as the group centre. Typically, the first shot from a clean barrel would shoot a bit high and left. The group size is the smallest circle that can be drawn to include the centre-points of all three holes in the group. I took the centre of that circle as the point of impact (POI) of the group. It is a long story, but to do that precisely turned out to be a challenging mathematical problem and led me to develop a computer program for assessing the data.
I plotted each group’s size and the POI variation versus the number of rounds fired without cleaning the barrel. The POI variation is how far each group centre is from the average group centre over the first 30 rounds. That is based on the presumption that the POI might wander as barrel fouling increases out past the 30 rounds fired mark and is arbitrary really.
Initially, you can see that the average group size (the red line) was consistent. Likewise, the POI variation average (again, a red line). Evidence of a loss of accuracy (group size and POI variation) would be an obvious sustained trend away from those initial values. I continued to visit the SSAA range, firing around 20-30 groups on each occasion. I was careful to avoid letting the barrel become too hot at these sessions because sometimes a hot barrel can influence accuracy. Once I thought the barrel was feeling too warm, I would retire the rifle to the rack and shoot another rifle. The weather did not cooperate much either. There was no rain but some blustery winds to contend with. How that affected results is hard to say, but not that much I feel.
I shot soft-points and polymer tips separately, as well as both together in one combined sequence. The end result was quite interesting. Apart from the slight inherent accuracy difference, the graphs of results demonstrated the same story for all the ammo I tested. From a hunting perspective, you can see that the claim of barrel fouling not affecting accuracy is largely true.
However, there was a slight but noticeable drift off in accuracy (group size and POI) out past about 150 shots, for my rifle and ammo. On the numbers, it does not appear much but from the graphs you can see an increasing number of fliers pulling the POI about. That sort of slight drift should be of concern to a varminter while not being of much consequence to a hunter of larger game out to reasonable ranges.
I did not take the testing of a non-cleaned barrel out past 350 rounds as I was starting to feel guilty about that and beginning to worry about how much cleaning was ahead of me. The cleaning surprised me though. With about twice the effort I would expend on cleaning a rifle after 30 rounds, I was seeing clean patches on my 300-plus round fouled barrels. So that was another interesting learning outcome from the whole exercise.
It seems that, for hunters at least, the particular range myth about barrel cleaning is right. You can fire a lot of rounds without worrying about significant loss of accuracy due to barrel fouling. However, I will not be changing my habits and will continue to clean my barrel every 20 or 30 shots regardless. It is one of those routines, like polishing your shoes, that is just a worthwhile thing to do, I reckon.