Barrel fouling and accuracy part IX

Tom68

New member
Okay, so the part IX was a bit facetitious, but it has been discussed a bit here in the past few years. I've been reading these posts for quite a while, yet I remain amazed by the wide variance I've seen regarding the topic. Some say they see accuracy fall off in as little as 40 rounds, while others claim to be 200+ rounds without cleaning the bore and seeing no degradation in accuracy. Can the curve really be so flat?

I'm guessing that it is indeed a flat normal curve. Just like some fit folks can run 2 miles without stopping while other similarly fit folks can run marathons without walking, rifle barrels also have a large standard deviation when it comes to barrel fouling and accuracy. All rifles and barrels are different, and thorough testing of my own rifle is the only way to fully ascertain what I'm working with, and regrettably, I've yet to perform such a test.

In all of my load development I have worked with a round robin method, shooting groups in a way that spreads the fouling amongst the several test loads which do not favor the first loads over later ones. The problem is, I have never fully determined how far to go without negatively impacting all of the test loads. So I've decided to test my rifle before further development procedures.

I intend to fire multiple 5-shot groups with one consistent load and determine how many rounds begin to affect accuracy. Beginning with a clean barrel, I expect to see the first one, or two groups spread out, as the initial fouling occurs; subsequent groups should shrink as we get into "the zone", and remain rather uniform, at least as well as my shooting from a rest will allow... And as fouling becomes a factor, group sizes should increase in a measurable way, given a large enough sample size. My intent is to determine the maximum allowable number of rounds between cleanings in order to set an optimum number of test loads to evaluate between bore cleanings.

So, what does the community think? I'm just trying to maximize my range time in testing load data. How does our group go about determining how many rounds is too much in comparing various data sets?
 
I'd be interested in the results but I don't think they are applicable to any other rifle/load. My rifles foul differently and that depends on barrel and the speed of the bullet, caliber, powder etc. if you determine accuracy falls off at 50 or 500 rounds, it would be an interesting data point but not particularly useful imo.
Additionally you'd have to take into account environmental conditions, wind, temperature and your ability as a marksman. Personally I have days where I shoot everything well and others I just can't get the potential out of myself. So you'd have to have a large group to average and it would have to be over multiple days. I'm sure there are statisticians that can give more scientific numbers.
 
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I'd be interested in the results but I don't think they are applicable to any other rifle/load.

I'd suspect the same thing but I'd be interested in your results anyway.

What caliber and rifle are you going to be shooting? (Not .22LR I hope.)
 
I'm a bench rest shooter, never let my barrel get to hot or my barrel get to fouled, 30 rounds max. Before cleaning. Never liked the idea of leaving the barrel fouled until your groups open up. Some people don't like to clean their rifle until something happens, simple as that. I clean but make sure to remove any cleaner or kroil oil before shooting, never needed foul shots from a dry barrel.
 
The particular rifle is a Savage model 10 heavy barrel with an HS Precision stock chambered in .308 Win. I'm not a benchrester, but for load development I am shooting off the bench with a Caldwell rest and a rear bag, trying as much as possible to eliminate the shooter from the equation and focusing on the rifle and loads being tested.

On a normal day for load testing I may shoot 10 groups of five each, working in 0.5 grain increments for one particular powder. I'm wondering if 50 shots between cleanings is affecting my groups and giving me bigger spreads than the simple observation that "more shots statistically produce larger groups".

As stated before, for load testing I normally do a round robin method, which essentially spreads barrel fouling across the entire set of loads, rather than letting the first group benefit from a cleaner barrel while later groups may suffer from more fouled barrel. All other factors (wind, temp, shooter temperament) generally remain constant in a single outing.

What I stated in my OP was an intent to try to find something close to a magic number of shots between cleanings in order to make my load development outings more meaningful. In these threads I have read of folks who can go hundreds of rounds without experiencing a degradation in accuracy, so I figured I'd try something to figure out where that number is for this particular rifle.

What I was originally looking for was some discussion on how some of you may have gone about ensuring that your load development experiences may have benefitted from a greater understanding of your rifle's tendencies as it relates to fouling in order to avoid wasting time and components. I don't necessarily like swabbing a barrel at the range, but if it's necessary in ordered to test 10 different loads of five each in a single outing, I'd like to hear of other's experiences.
 
The fouling/accuracy relationship varies significantly IMO based mainly on barrel quality and finish (or wear) inside the bore. This is the one factor where I believe barrel break-in (basically barrel wear) makes some difference. I've bought several new (Savage and other) rifles over the last 10-15 years and while I won't say they got any more accurate once "broken-in", they do seem to maintain accuracy for more shots and accumulate less metal fouling after they have a few hundred rounds through them. I believe due to smoothing (wear) of the small tooling marks that exist in factory barrels that are not hand lapped or otherwise final finished before shipment.
 
What I was originally looking for was some discussion on how some of you may have gone about ensuring that your load development experiences may have benefitted from a greater understanding of your rifle's tendencies as it relates to fouling in order to avoid wasting time and components. I don't necessarily like swabbing a barrel at the range, but if it's necessary in ordered to test 10 different loads of five each in a single outing, I'd like to hear of other's experiences.

What you will get from cleaning a barrel before shooting is your CCB or "clean cold bore" shot. With a decent factory rifle, the CCB shot can be 1.5 to 2 inches out of normal fouled bore group.

If your rifle "walks" the groups into a repeatable tight group as fouling grows, your rifle will shoot better with a fouled bore. If you rifle has just one shot out of group from CCB, then simply knowing where your CCB will fall is important for first shot repeatability.

As far as knowing this for load development, it is why you should do your load work up on a fouled bore and once you find a good load, then do the CCB work to find out how your rifle performs with that load with CCB.

Jimro
 
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