(BTW this is my first question, sorry if this is bad.)

So basically, in my world there is a race of octopus-like aliens who use handheld firearms, now the question is how would they design them. Now humans have effectively figured out a basic design pattern, the barrel, then the stock after the barrel and the firing mechanism under the barrel. Now my question is would this change when they are made by cephalopods.

The species:

* Are cephalopod like with 12 tentacles
* 6 of them are tough but less opposable and 6 more opposable
* They do not have a skeleton.
* They move around on 6 of their tentacles by "crawling" around (However they only require about 4.) They hold onto things with 1-3 of the other 6.
* They are about 100-150 cm in height and 80-120 cm in width on average. The mass is about 30-55 kg on average.

About the firearms, the requirements are:

* They have to be operated by only a single user.
* They are single shot muskets (Barrel loaded.)
* Have a trigger system.
* Earthlike conditions on land are presumed.