Baher 23mm heavy rifle was unveiled by way of an Iranian military day parade in April of 2015.
Baher-23 is a new gun adopted by the Iranian military for the very-heavy-sniper-rifle role. It fires a large 23mm projectile, a cartridge much more closely associated to some small-caliber cannon compared to rifle, at ranges out to 5 kms. The weapon is actually primarily intended for beating helicopters, light armored automobiles, and enemy staff hidden behind fortified walls though absolutely nothing excludes it from engaging personnel straight – of course along with truly devastating outcomes.
The weapon is really a complete sniping process, requiring an operating crew of 2 to 3 personnel and with a weight some 62 kgs. It has been featured on the special heavy-duty, flexible tripod assembly made to absorb some of the naturally violent recoil organic to a weapon of the caliber. The gun is given more conventional components as well such as an optics arranged fitted over the recipient, a pistol grasp, and shoulder stock. The extended length clip or barrel is capped with a large, slotted braking system.
http://www.tasnimnews.com/fa/news/1394/08/10/903858/ایران-با-باهر-صاحب-نیرومندترین-تک-تیرانداز-جهان-شد-عکس
Just looking at caliber, then there is the Barret XM109.
The Barrett XM109 is a prototype anti-materiel rifle and grenade launcher, chambered in 25 × 59 mm, developed by Barrett Firearms Manufacturing. It was designed as a modification of the Barrett M107 and was capable of defeating light armor and equipment out to 2 km (1.2 mi). Weight 33.2 lb (15.1 kg)
Barrett XM109 - Wikipedia, the free encyclopedia
But really, one has to compare the rounds.
RT-20 (Croatia) uses 20×110mm Hispano
Vidhwansak (India) is available in 12.7×108mm (.50 Russian), 14.5×114mm and 20x82mm
Denel NTW-20 (South Africa) is available in 20x83.5mm and 20×110mm
Truvelo SR-20 (South Africa) is available in 14.5×114mm, 20x82mm and 20x110mm
So lets look at 20x110 at Tony Williams excellent site
ANTI-TANK AND HEAVY MACHINE GUN CARTRIDGES UP TO 19 MM CALIBRE
weight = 122-130 gram (HE round, not AP)
muzzle velocity 830 to 880 m/s
20x82 is less powerfull
weight = 115 (HE round, not AP)
muzzle velocity 710 m/s
I'm assuming Iran has used the 23mm round that is common in Russian weapons (ZU-23-2 aaa, aircraft cannon)
Aircraft cannon use 23x115, which weighs 175 grams and has a muzzle velocity of 740 m/s
AAA cannon use 23x152B, which weighs 185 grams and has a muzzle velocity of 900-970 m/s
See
21-29 MM CALIBRE CARTRIDGES
So, it really depends on which 23mm round is used to determine if it is better/worse or lighter/heavier than e.g. 20mm rounds. 23x115 is heavier than both 20x82 and 20x110 but the latter is significantly faster and may have better penetration for a lower weight. 23x152B outperformes both 20mm in projectile weight and muzzle velocity.
Note though that this is HE rounds!
For anti-material you might use a apfsds round (subcaliber munition), which I assume would be lighter. Perhaps muzzle velocity is the most critical variable here then.
More on sniping ammunition here
Cartridges for Long
More on anti-tank rifle ammunition hre
An Introduction to Anti
TRANSITIONAL ANTI-TANK RIFLE: THE CARL GUSTAV M/42