What makes a good bolt action to me is good iron sights, good ADS (Though all bolts are very similar in stat here with no actual outliers within the tree) and good fire rate (as close to if not more than 60 RPM preferred). From there damage over 27 ((10+3.5)x2) is preferred if possible. These are my personal choices:
USSR:
IMO, the first 3 bolts iron sights are just poor, this leaves the M44, M91/30, and M1895.
The M44 has best iron sights of these 3
The M91/30 is jack of all trades, master of none.
The M1895 has higher damage and better ROF, while having serviceable sights. It is also a lever action technically, but the sound is awesome IMO. Along with its ability to pass the 27 damage threshold at CQB ranges, it is the clear winner, though its lack of a bayonet does mean the purchase of an axe for charge functionality.
USA/UKC:
USA/UKC actually have a few great options, while the starting rifle’s irons are garbage, you do quickly get a very solid rifle in the USMC Springfield.
The Ross Mk III has a great ROF but no bayonet and the irons can be quite nice especially at long ranges. Have had plenty of fun with this rifle. I personally hate the SMLE MkIII’s sights and constantly use the right sight post subconsciously. The Enfield is better in this regard and its added internal magazine capacity is great … but if you run cqb, having to break the reload animation can also be a negative in certain situations. Due to my aggressive playstyle I do tend to run into CQB a lot more with bolts and rely on strafing heavily to gain chain kills. I find the Enfield’s longer reload actually hurts me more than helps me in heat of the moment, as well as it being BR III. As such, my go to tends to be the USMC Springfield.
Germany/Italy:
Germany/Italy has, IMO the strongest starter rifle with best iron sight style and respectable fire rate. While the Kriegsmodell is horrid, the standard K98 is quite nice. The Carcano Mod 38 (7.35mm) is however a very good and is a worthy addition. You then get a series of just really poor iron sights and ROF weapons. The Vz 24, the Pre-war, The Mannlicher, MAS-36, and M1891 are just skips imo. The Pre-War and Mannlicher I found great on paper, but the iron sights I just don’t like. Though, I have had fun with the M1891, the Mod 38 is objectively a better Carcano rifle. The VG.2 however is a great bolt being a magazine fed with solid irons and ROF, though it does lack a bayonet. It also being in BR III does let it fall as the Enfield does. My normal pick is the Carcano Mod 38 due to its compact design, iron sights that are tolerable, and great ROF.
Japan:
Japan is a tough one, as there isn’t a “Great Bolt Action”, IMO. The Type 38 rifles have poor iron sights, as does the Type I and 99 (Late). The only one with decent iron sights is the Type 99 (early), but it lacks ROF. Early on, I would go with the Type 38 Rifle (non carbine), but I tend to rock the Type 99 Early due to the iron sights being more clear to me and the better damage.
To be clear, this is my opinion and your play style and preferences may result in different preferred weapons.