This may data help - data based on 1060 5-round groups at 100 yards with my 12 FV .223 with an Oryx chassis and a 26-inch barrel that is marked as a 9 twist.

I listed powders, weight, and bullets for 69 through 77 grain bullets.
I find that this rifle shoots 73 and 77 grain bullets really well, even thought Sierra and Hornady print on their boxes that they should only be shot in barrels with twists of 8 or faster.
Perhaps my barrel is closer to an 8.5 twist than a 9 twist.
Your barrel will probably have different bullet and powder preferences, but this may give you some ideas.

Sierra 12 FV .223 Oryx Chassis 9 twist & 26-inch barrel
# Rnds Powder Bullet Wgt Avg Best Vel
2 IMR4166 Nosler CC #17101 69 0.403 0.403 2953
13 IMR4166 Nosler CC #53065 69 0.310 0.358 2584
7 N540 Nosler CC #53065 69 0.283 0.314 2682
18 Varget Nosler CC #53065 69 0.258 0.227 2633
15 N140 RMR HPBT 69 0.296 0.303 2649
8 N540 RMR HPBT 69 0.322 0.290 2649
8 Varget RMR HPBT 69 0.286 0.258 2634
93 IMR4166 Sierra SMK # 1380 69 0.292 0.287 2590
32 N140 Sierra SMK # 1380 69 0.289 0.295 2654
34 N540 Sierra SMK # 1380 69 0.246 0.215 2680
24 Varget Sierra SMK # 1380 69 0.233 0.205 2672
6 H4895 Sierra TMK #7169 69 0.312 0.333 3042
96 IMR4166 Sierra TMK #7169 69 0.287 0.288 2586
39 N140 Sierra TMK #7169 69 0.288 0.299 2643
8 Varget Sierra TMK #7169 69 0.251 0.261 2617
11 H4895 Berger VLD #22418 70 0.286 0.254 3034
3 IMR4166 Berger VLD #22418 70 0.291 0.291 2581
6 H4895 Nosler RDF #53066 (2nds) 70 0.298 0.388 3036
8 N140 Nosler RDF #53066 (2nds) 70 0.280 0.267 2634
4 Varget Berger VTB # 22420 73 0.251 0.251 2606
8 H4895 Hornady ELD-M # 22774 73 0.264 0.251 2606
7 N140 Hornady ELD-M # 22774 73 0.273 0.262 2619
16 N540 Hornady ELD-M # 22774 73 0.238 0.230 2648
8 Varget Hornady ELD-M # 22774 73 0.216 0.214 2605
3 Varget Berger VLD # 22421 75 0.341 0.341 2605
4 N140 Hornady ELD-M # 22791 75 0.375 0.353 2604
17 N140 Berger OTM #22101 77 0.282 0.279 2598
4 N540 Berger OTM #22101 77 0.275 0.275 2620
8 Varget Berger OTM #22101 77 0.271 0.295 2584
12 H4895 Nosler CC #53064 77 0.280 0.274 2999
9 IMR4166 Nosler CC #53064 77 0.227 0.216 2760
4 N540 Nosler CC #53064 77 0.274 0.274 2629
12 H4895 Sierra SMK # 9377 77 0.237 0.195 2993
93 IMR4166 Sierra SMK # 9377 77 0.293 0.344 2546
83 N140 Sierra SMK # 9377 77 0.289 0.223 2599
22 N540 Sierra SMK # 9377 77 0.240 0.226 2613
16 Varget Sierra SMK # 9377 77 0.270 0.262 2578
205 IMR4166 Sierra TMK #7177 77 0.279 0.207 2539
61 N140 Sierra TMK #7177 77 0.282 0.229 2592
4 N540 Sierra TMK #7177 77 0.283 0.283 2613