At what point did you:
Adjust powder charge to maintain velocity
or
Notice velocity decrease
Many of use consider a barrel done for competition once it starts losing velocity/needs monitoring for powder increase. Which is a distinction most don’t make when talking barrel life.
Barrels have two points:
Where velocity starts to get finicky
Where accuracy starts to get finicky
Both have their uses as far as barrel life. Sometimes they coincide with another and other times not. I’ve had barrels slow down and remain accurate and other barrels totally burn out and lose accuracy and velocity at the same time.
I don't have enough experience with it to tell you for sure. I have two more barrels to shoot through, but my wife just got a 6 dasher. We'll see if I continue to shoot 243ai or switch to a Dasher. There are things I like about both.
The first barrel was my foray into long range shooting. I shot 105 AMAX for around 700 rounds and then developed a load with 115 DTACs. I started shooting matches and finished burning up that barrel in less than a season. When I developed the load at 700 rounds I jumped the bullets .040". That load shot lights out until the barrel gave up. I didn't have a magnetospeed at that time, but I didn't notice a change in dope until after 2000 rounds through the barrel. The barrel was cleaned every 200 rounds with gunslik foaming cleaner and JB borepaste in the throat. It would no longer hold vertical at distance at 2600 rounds.
The second barrel I tried a whole bunch of stupid shit with. I still cleaned and JBed the throat every 200 rounds, but I also shot 2 TMS bullets every 200 rounds after I cleaned the barrel, and then cleaned again to clean out the garbage from the TMS bullets. On the first barrel I did not measure the throat or check velocity. On the second barrel I measured the throat every time the velocity dropped and after every cleaning I shot dots for 15 rounds and then shot 10 over the magnetospeed. At 800 rounds I lost 40 fps and the throat had shot forward quite a ways (would have to look at my notes). The load with the second barrel was only .010" off the lands. I chased the lands and added powder and the thing shot for another 800. At 1600 I had lost about 40 fps again and the throat had grown a ton. I stopped shooting TMS bullets at that point. I chased the lands and added powder and that load shot and chronoed the same until around 2500 rounds. At that point everything went to hell. I had chronoed at 2400 rds, but I didn't rechrono when the accuracy went to shit at 2500 rounds. I just called it dead.
I'm just under 200 rounds into the third barrel and ready to get into serious load development. I'm going to try jumping .040"+ and see if the load will hold longer on this barrel. I also switched from a Savage action to a TL3 and started loctiting the barrel nuts, so I can switch barrels easily and maintain the same headspace. I'm going pull the barrel and clean the throat on this barrel with CLR and use a borescope instead of using abrasives and see how it goes. I honestly think the way you clean and the distance to the lands when you develop the load has some bearing on how long the load holds. I'm only 2 barrels in, so until I have 8-10 barrels burned out with the same caliber, reamer, load, and cleaning routine I don't think we can draw a lot of solid conclusions.
I just cleaned the wife's dasher at 220 rds and the throat has not moved a measurable amount using the Wheeler method to find the lands. She's running 32.0 gr Varget under a 105 at 2880, so not pushing it hard. Even then, there isn't a lot more wind to hold than my 243 AI and it was stupid easy to find a load that shot under 1/2 moa. If the barrel life is a lot longer, and there is less fussing with chasing the lands, etc., I may have my next barrel chambered in 6 Dasher. The only real drawback I can see is that a 115 DTAC going 3050 hits targets noticeably harder and is easier to spot misses with than the 105 at 2880. I even notice the 115 at 3050 is easier to spot misses with than the 105 at 3150 out of my 243AI when I switch back and forth.
The big 6mm cartridges definitely have drawbacks, but so do the little ones. I was simply stating that there are ways to extend the barrel life beyond the 1200-1800 rounds that has become the expectation for 6 Creed running 4350 while still getting the same velocities. It would be nice if barrels were free, and then I would just shoot them in matches from 200 rounds to 1200 rounds and switch and use the barrel with over 1200 rounds on it to practice. Until then I'm going to use 223 to train and save the barrel burners for matches and hunting.
It will be an interesting experiment to run the 243ai with H1000 next to the wife's 6 dasher for several barrels and compare them. It will be a while before there's been enough shooting for a real comparison as we only shoot around 3000 rounds/year through our match guns.