Mobile Augmented Reality (AR) technology is enabling new applications for different domains including architecture, education or medical work. As AR interfaces project digital data, information and models into the real world, it allows for new forms of collaborative work. However, despite the wide availability of AR applications, very little is known about how AR interfaces mediate and shape collaborative practices. This paper presents a study which examines how a mobile AR (M-AR) interface for inspecting and discovering AR models of varying complexity impacts co-located group practices. We contribute new insights into how current mobile AR interfaces impact co-located collaboration. Our results show that M-AR interfaces induce high mental load and frustration, cause a high number of context switches between devices and group discussion, and overall leads to a reduction in group interaction. We present design recommendations for future work focusing on collaborative AR interfaces.