243 Accuracy Issues - Impact of carbon buildup

[264WinMag]

I would say no, carbon will not do that within 15 shots.

I think you guys witnessed some symptoms and associated the fix with cleaning without a complete documentation of events.
Anyways, if you guys did shoot at 3300ft/s you would have put enormous strain in the action, my first thought would be bedding, not barrel.

Taking into consideration the high speed it can be a factor. The rifle was recently bedded with stainless steel pilars and packed.

What we did notice that the rifle grouped very well with the 41.2 load and after a few shots did not group with the same load. After cleaning it grouped again.


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[Dale SH]

Get a second opinion on the condition of the barrel.

[Dale SH]

3300 fps from your barrel length using 44.2 grains S355 would put your chamber pressure at around 76000 psi.
Please do not let your friend do anymore QL calculations for you.

[A-R]

back to the original question. Can barrel fowling happen so quickly to affect accuracy?

Yes.

But we are talking about fouling (dirt accumulation) not fowling (wingshooting). Laat die Boertjie jou nou Inghils leer!

I have seen this happen with fewer shots in a rough bore. Basically the jacket material and carbon fouling accumulates around the sharp edges of the pit marks and affect the bullets. Your chemical cleaning removed the fouling and restored the accuracy.

Since the particular rifle was built a few decades ago, it is quite possible that it has been shot a lot and maybe even neglected a little. This could explain the rough bore.

You could try to use a (soft) abrasive cleaner like JB Bore Paste or even Mr Muscle (formerly Brillo) and skip the chemical solvents. This method will remove any fouling that obstructs the bore, but not any that sits inside the cavities (pit marks). Over time the cavities will fill with fouling and the barrel will get smoother. Some target shooters swear by this method. It is important to not over-do the abrasive cleaning, as you don't want to convert your 243 Win to a 260 Rem.

May be worth a try and postpone the inevitable barrel replacement for a few hundred shots?

P.S. Your friend's QL skills are dangerous!

[Messor]

If he used a dual solvent, which removed both copper and carbon, I would agree with you AR.

But carbon alone, dunno.

Maybe they should have kept on shooting and see what happened.
Not with that silly hot load of course, just a normal load.
Copper accumulate in a barrel, often covering small imperfections, I have read on overseas forums where some barrels shoots better after 30 or 40 shots.

[264WinMag]

Thank you for all the input.

From the advice provided, I am getting a vague idea that the load was a bit hot ;). Thank you for the warning it is noted and will be remedied.

AR - I have issoo bore paste which I have used in my 264 which worked great. We clean the bore with this and see where we end up.


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