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finicky barrel

16 Oct 2023
@ 05:47 am (GMT)

Oliver Rau

it is the rifle, this story started with.
a Winchester Xtreme weather 300 Win mag.
it was finicky quite from the start. a one time 3-shot group of half moa at 330y wih hornady factory ammo, but that was it. From there on groups from 1-2 moa. i thought i have had it and sought to find it again. read all of Nathan's work, started reloading, even bedded the rifle with much sweat. after many, many rounds i found a quarter moa load (sometines). at that point i only knew the barrel was a fast fouler, 3 foulers and i was good to go? further testing revealed that peak accuracy was pretty short 2-3 shots, then groups opened up again and POI wandered as well, around 3moa. no good for hunting.

so i did the scotch brite treatment (maroon) after a thorough clean, still some of the copper remained mostly at the muzzle. this seems to be what Nathan describes as plasma deposits, pretty stubborn. the patch took care of it.

but accuracy and POI change still is not satisfactory. first of 3 is always an outlier deep left. next 2 about 0.7moa apart and center still changing. repeated 3 times, no cleaning between.
inspecting the barrel after 8 shots revealed astonishing little copper fouling. a liitle in parts of some grooves and some edges between lands and grooves seem to have rough spots still where copper accumulates. but altogether pretty little compared to before, even stripping of with a cleaner which has proven not to be aggressive against copper/brass.

so now i am wondering do i need more fouling for the barrel to settle in? i mean my trg takes 30 shots after thorough cleaning, but that is a 308 and no magnum.
OR do i have to repeat the job?
any answer is highly appreciated as this rifle seems to be the last of its kind (here in europe). kind regards Olli


16 Oct 2023
@ 06:38 am (GMT)

Nathan Foster

Re: finicky barrel
Hi Olli. It sounds as though the book instructions worked. A note to others - these methods are also shown in trouble shooting video

Leave it at that for now. It sounds as though it is not producing a high level of copper fouling, leaving at least a small window for load investigation. One factor I have learned through ongoing R&D on this subject, is that the key word is resistance. I believe what we are looking for is consistent resistance so that the bullet does not experience significant harmonic changes as the bullet traverses the bore. If resistance continually increases, the harmonics continue to change. If there is very little resistance, we can run into problems relating to the coefficient of friction (as related in the books). What I have found, is that the sweet spot (grit size of bore finish) is a relatively small window so once we get into the ball park so to speak, it can pay to avoid any further major changes.

Harmonics is of course an issue with any light barrel, especially if running a potent cartridge. The Extreme has the additional problem of having a fluted barrel - so much so that it may eventually swell within the fluted section.

For this next phase, I suggest that you remain focused on harmonics but rather than focusing on altering the rate of fouling, look toward load development. You may have to back off loads a bit. For example, you might want to try experimenting with a soft heavy high BC projectile travelling at about 2650fps. I know this sounds very slow but it may help offset any stress within the bore while the low pressures may also help the barrel last a little longer (minimize swelling).

This is about as far as I will advise on a public forum without having the rifle in hand (not having all the facts) to inspect for myself.


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