Home Forums Hunting & Shooting Custom Rifles & Wildcats Throat erosion - .243 vs. .243 Ackley Improved

Aren't Ball powders all or mostly double base powders? And I believe they are so wouldn't they be harder on a throat than a single base stick powder?

I only know what I've read - generally - so this time decided to see for myself. The quotes below are some of what I've read. I've only shown those portions of the threads relevant to questions in this one, but lest I be accused of taking them out of context links to the original threads are included so those interested can go back and check for themselves.

All quotes are from Mule Deer and extracted from threads on the .243.

http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/1529522/1
"The .243 tends to erode throats faster than other rounds its size, probably because of the geometry of the case. The sloping shoulder and short neck tend to send hot powder gas right into the bore just ahead of the case."
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"6mm Remington barrels do tend to last longer than .243's, probably because of the longer neck and steeper shoulder.

The same problems that occur with the standard .243 are MUCH reduced with the .243 AI."
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"Montana Man,

Yeah, powder can affect barrel life. I generally run the cleanest burning powder I can, which cuts down on both powder and jacket fouling. Both have some effect on accurate barrel life.

Single-base powders have a lower burning temp than double-base. This supposedly does help in the long run, but the big factor is not frying the barrel with too many fast repeat shots."
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https://www.24hourcampfire.com/ubbth...e/Re_Mule_Deer_others_re_243#Post3677696

"The .243 is generally considered a throat burner. This is not just due to the bore/capacity ratio, but the fact that (as Ramblin' Razorback suggested) the rather sloping throat and tends to direct gas toward the throat just in front of the short neck. Thus it's partly a problem of gemoetry."
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"If the neck were quite long on all cartridges that would be true, but the gas is directed some by the shoulders before it gets into the neck--and if the neck is very short (as it is in the .243) then some the gas coming off the shoulder blasts right into the sides of the throat just in front of the case mouth.

Take a look at a .243 case, or a drawing of one, and you'll see what I mean. With other commercial rounds based on the .308 case (all of larger bore diameter than the .243) the neck is longer."
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I remember some other discussions about the properties of the .243 and how AI'ing mitigates or reduces them but hopefully the above will suffice to help explain some of my reasons for wanting to AI the barrel in the first place and perhaps to add some credence to the results of my little "experiment".

As a .243 the barrel saw rounds loaded with 100 grain, 85, 80 and 75 grain bullets using IMR4831 (call it 50% of those loads), about 45% H4350 and the rest a tad of IMR4350 and some RE-15.

As a .243 AI it has seen 100, 107, 87 and 85 grain bullets fueled about 90% by H4350 with some RE-15 and maybe 30 rounds using Hunter.

So the powder mixture was a bit different but I don't think there is a lot of chemical difference between IMR4831, IMR4350 or H4350 which accounted for the vast majority of rounds fired in both chambers.

Rate of fire was exactly equal - mostly 3 round strings in the space of 2 minutes or so. Several 4 and 5 round strings spaced out over 4 to 5 minutes.

This wasn't by design, that's the rate of fire I use for all my rifles. Bench testing gets 4 or 5 round strings, after that I'll get off the bench, load three in the mag and practice from kneeling or offhand, firing about as fast as I can work the bolt, breathe, steady down, aim and squeeze off a well aimed round.

Those three rounds get the barrel warm but not hot to the touch, even in summer. After three shots the rifle is set aside to cool while I shoot my other rifles.

Whether as a .243 or .243 AI, the barrel was never shot to the point where I could not comfortably lay my hand on it.