This 4 photos are in PB report.
These photos are as same as Photos of Type5 Anti Tank Gun in original report by Japanese Army.
So I think that these 4 photos Guns are Type5 Anti Tank Gun(Nato Gun).
Type5 Anti tank gun's Gunbarrel and Breach block and cradle are same as Type 5 tank gun.

Type5 Tank Gun Model2 for Tito/Type4 Tank.

Type5 Tank gun model2