the gas ports are the same, the bulgarians use a different gas block on their 104/CR rifles. unfortunately the barrel is turned down to thin to mount a front sight, might be possible if you knurled the barrel but a new barrel is the best option.You would do well to arrange a complete barrel trade or weapon trade with someone with the full length barreled 107, since the gas ports are in different locations. There are actually many differences between an Arsenal SLR-107 and a Russian AK-103 also by the way, if that matters to you, they just generally look similar. There are likely many folks here that would like to have a 107 CR, they are very desirable for some and trade should be easy to find.
k-var was the only ones who stocked them and i believe they were takeoffs. you can get a barrel and all the small parts from them though.I can't find a 103 barrel assembly anywhere online. Anyone know who has them in stock. If not ill just trade it