I am going to say, go for the 24" barrel, or better yet, the 29" barrel! I have some data with Swedish ball . The military rifles even though the barrels are two inches longer, they have to be looser than the 22" M700 barrel. The round really picks up speed in the 29" barrel.
Just because the Cavalry had a 17" barrel does not mean that it was a great choice in 1894, and, they got rid of it. The later Cavalry models had 24" barrels. Go with the 24"
M700 22" Barrel
140 gr Hornday Spire Point 43.0 grs AA4350 R-P new brass CCI-200 OAL 2.990"
2 Feb 2008 T = 52 °F
Ave Vel = 2512
Std Dev = 27
ES = 72
High = 2547
Low = 2475
N = 5
143 gr Swedish Ball 1986 headstamp
2 Feb 2008 T = 54 °F
Ave Vel = 2470
Std Dev = 18
ES = 48
High = 2491
Low = 2443
N = 5
M38 Calvary Carbine 24" barrel
143.5 gr FMJBT Swedish 1986 ball. OAL 3.065" 47.4 grs powder average
20-Mar-94 T ≈ 78 °F
Ave Vel = 2477
Std Dev = 23
ES = 57
Low = 2449
High = 2506
N = 4
M38 Infantry Carbine 24" barrel
143 gr 1986 Swedish Ball
28-Oct-94 T ≈ 60 °F
Ave Vel = 2427
Std Dev = 22
ES = 62
Low = 2395
High = 2457
N = 10
M1896 Infantry Rifle 29' barrel
143 gr FMJ 1986 Swedish Ball
17-Aug-06 T = 85 °F
Ave Vel = 2610
Std Dev = 14.38
ES = 45.59
High = 2633
Low = 2587
N = 8