Is there an in univeres explanation for transformers suddenly using guns instead of transformed parts of their bodies?

In the first 2 films the transformers transformed parts of their bodies into guns (for example bumblebee and ironhide are seen in closeups doing that. Also the cubeinfected items do that). In the films 3-4 all of a sudden they use hand HELD guns and swords (in 4 we see them running out of ammunition for the first time even) instead of transforming parts of their bodies like in the films 1 and 2.

So my question here is: IS there any in universe explanation for this (aside from the script writers suddenly finding hand held guns and swords cooler after 2 films not using them)