The .243 Ackley is a great round. I certainly have enjoyed mine. It does however take a back seat to my other rifles and only because of it's limitations of effective use and that it's a puropse built rifle. I have taken a few Muley bucks with it. Neither required a second shot and both went down quickly.
What is the intended use for your rifle? What twist is the barrel???
Mine has the standard 9 1/4" twist bbl so I'm limited to 100g Bullets. I may choose to rebarrel my Rem 700 VLS .243 with a 1-8" twist barrel with the intent of using 115g Bergers, as well as chambering it to the .243 AI as well.
My .243 AI was also my first Ackley cartridge. I learned alot about fireforming and load work up as a result. It's one of the easier Ackleys to start with. Some things I learned and had trouble with (this is unique to my rifle, I bought it used and it was chambered already.) were:
1. necks splitting with Fireforming. I used Virgin Brass to fireform to the Ackly Chamber and lost 10% of my first round of cases. I decided that I would form my cases out of Military .308 Cases and use Lake City Match. I Bought a neck turner and necked the cases down in stages using .260 Rem dies and then to .243 Win, Then I turned the necks to fit the throat. Loaded and Fireformed.
2. since I was using military cases, I was able to reduce the powder charge and achieve the same result. The brass is much stronger and I haven't lost one yet.
3. Medium burn rate powders work best like 4895, H414, or 4350 or even RL 19. I'vehad best accuracy with H414. H4895 Worked best with 95g Nosler Balistic tips.
4. Shots on big game were kept to 350 yds or less. I wouldn't hesitate to use it on Elk with in 100yds, If it was the ony rifle I owned. fortunately I own others. Coyotes are aq diffrent story. This thing is deadly out to 500yds so far.
5. Ackley become addicting and I've enjoyed all three.
I can only speak highly of the .243 AI. If you have any questions or if I can help, let me know.
It's a standard Remington SPS takeoff, so I dont think its twisted especially well. Probably will just shoot the 95 gr BT and some SMKs. My brother as a youngster took 2 elk with a standard 243; one at 195 yds and one at 250. As far as I'm concerned I'll use this rifle to shoot steel and coyotes with, and my sister may hunt with it. But I have no concerns about its lethality on game, especially when fed TSX.
It'll have a 9 1/4" twist as well. It's going to be a good deer round for sure. You'll be able to get 3100-3200fps with the Barnes TSX, but the heaviest bullet they make is 85g. I still think that it is light for elk, but for deer it would be great.
I saw a 5 point bull elk take 4 hits all of them good solid vital hits from a .300 RUM using 180g TTSX before it went down. I have like wise seen elk go down with .243s. I just try to give the elk the benfit of the doubt and use a bigger rifle if I can. Remember this is my opinion, you can do what you want...
It seems your rig will be similar to mine. Targets and coyotes beware. have fun with it and good shooting.