"Loads" of good info. Thanks. Some background, years ago when I started shooting prairie dogs one of my buddies talked me in to the 243AI. Speed was definitely a consideration as it's always fun to see a prairie dog jump, but also I was told that the 40° shoulder directed the combustion more to the center of the bore resulting in longer throat life. Later I decided that speed wasn't as important to me as throat life and cost of powder. Also, much of the load data for the standard 243 stop with maximum loads resulting in under 3000 fps, so to be honest I haven't done much testing with the extra 7% volume of the AI cartridge, and I don't have much information about how higher velocities affect accuracy. So I'm definitely not taking full advantage of the cartridges abilities. Because of age and the passing away of some of my shooting Buddies I'm pretty much relegated to targets these days.
Gotcha, makes sense, I am not opposed to having the capability of a 243AI but loading it down if you are not trying to get the most potential out of speed.
I use a 6x284 and have for over 30 years, it never gained much popularity
I latched on to it myself for ELR shooting when nothing else would compare but a 50 BMG
And I was NOT about to use a 50 for fun shooting mass amounts fo ammo haha
So I have stuck with a 6x284 and have never been let down by that choice.
You are correct in the Ackley 40 deg shoulder helping things, the 6x284 has a 30 deg which is good enough, and if it were steeper may impede quick chambering and cause feeding problems
A 6x284 case with 115's is VERY long so a bullet may hit the top of the chamber when trying to feed before it straightens itself out, so I stick with a 30 deg shoulder for it.
My last barrel shot accurately for 1900 rounds so yes they are a barrel burner but not as bad as most people make it out to be if you are conservative in how hot you shoot it.
-------
How many guys have several barrels chambered up for a 6ppc or 6 BR?
Do the same with a 6x284 and quit complaining of barrel life haha as if a guy expects one barrel to last a lifetime or something,
-------
When years ago the 243 AI gained a lot of popularity and newer powders were coming out offering much more choices than we used to have
I was seeing guys with a 243AI getting something like 3300 fps with a Sierra 107 (Rl 25 comes to mind)
Which is only 100 fps behind a 6x284
I ALMOST, decided to try a 243 AI just because it uses less powder to get almost the same velocity
Meaning (a more efficient cartridge) But I was already tooled up for 6x284 so never switched.
I like the 243 AI and what it is capable of, it has a lot of potential with the right barrel and twist rate
And yeah Prairie dogs at a mile is what really showed me the capability of a fast 6mm
When 3 guys with 6x284's are knocking them over at that distance, it speaks volumes of the cartridges capability.
-----------
As far as higher velocities affecting accuracy, I have not seen any correlation
as mentioned I have driven bullets to the point of failure while still retaining accuracy
I only load down enough to stay within a safe margin for temp conditions
For myself, 3200 fps is fast enough, nice flat trajectory however I use 3400 fps as a safe target number for developing my accuracy loads (if the bullet can handle it) Seems to be a node right around 3385 fps
a good enough node that the seating depth window opens up to be fairly forgiving
I can seat from 3.470 to 3.500 (CBTO Length)
