If the problem is just the distraction
If you think this isn't going to go away then you should raise it with your line manager as a difficulty you are finding with your workplace environment. Any junior employee should get some help and support with this kind of difficulty. It would be the same if the distraction comes from company-critical activities or building work in the street outside, although the options to deal with it are different. Your line manager could move you out of the crossfire or at least give you advice how to work through or around distractions.
You should accept that it's possible nothing will change. Your employer is not obliged to give you a workplace that is free of distractions, and you are not required to remain un-distracted no matter what goes on around you. It's not up to you whether nerf guns are fired about the place, it's up to whoever manages the team. But there's no reason your line manager shouldn't take into consideration that it's a problem for you. One option, therefore, is to accept that this activity is distracting, accept that once it starts you will get no work done until it stops, and join in! Check with your line manager that it's OK to timesheet it as "internal communications meeting" ;-)
Managers make a decision on a compromise that suits their goals, depending on the preferences of various members of the team. They are obliged (by common sense if not by law) to take into account the effects of their decision. Some managers will duck this responsibility -- dealing with bad managers is a whole separate issue from dealing with annoying colleagues. So, if you find your line manager totally unsympathetic and unwilling to engage in the issue then you have a new question on your hands.
You say in a comment:
It just gives us the perception for being a team of clowns.
You shouldn't worry about this, it's not really your concern unless you think the rest of the company will judge you primarily by this one aspect of the behaviour of the team you belong to. If your team truly is perceived as clowns by the rest of your company then it's unlikely that of your team, only you have noticed this. But just in case, you could think about cautiously reporting some of the comments you've heard from others. If your team is not generally perceived as clowns, but you perceive them that way, then think about who is more likely to be right (and who has the right to decide what's an acceptable level of clowning around) -- one junior employee or the whole rest of the company. So, they're clowns. When you build a team from scratch, you can decide that you want it to be a team of non-clowns. This is not that team.
If the problem is senior colleagues are shooting at you
Unless there's something peculiar in your contract or your job description, you are entitled not to be targeted yourself if you don't want to be, so do not feel that you must tolerate stuff being thrown/fired at you. If they're shooting you and you want them to stop that aspect of it, then you can ask them (calmly and politely) to stop. Most people are not such jerks as to continue after that, so in most places that will be the end of it. If you don't want to address them directly then go through your line manager. If you ask them and they don't stop, again go to your line manager. Remember that you're not trying to stop them shooting each other, your goal is for them to stop shooting you.
Now, it's possible that the team will dislike you for "not joining in" or "not having a sense of humour". This is called bullying. Most people who engage in bullying aren't terrible people, they just haven't really thought through the effects of them imposing their idea of "cool" or "fun" behaviour on people who do not enjoy that behaviour at all. Perhaps they need help seeing that launching stuff at people might make that person feel uncomfortable or threatened. They will generally say that they are not bullies, rather that there is something wrong with you for not enjoying what they do to you. They probably truly believe that, because although everyone knows that the thing called "bullying" is wrong, they aren't necessarily capable of realising when they're doing it. That is all part of the bullying.
If you're bullied there may not be much point telling your line manager or HR in so many words that you're being bullied. You're better off sticking to reporting specific actions and incidents. However, when an organisation supports bullying your line manager will favour the bullies, will say that you need to take a little hazing to fit in, that everyone else puts up with it, etc. It is incredibly difficult to uproot this culture, and one junior member will not manage it alone. Expect to move on one way or another, perhaps an internal transfer to a less aggressive group if the company has several teams. It's possible, but unlikely, that you have simply stumbled into a nest of intolerable jerks. For example, if your company sets its standards by those of professional sports teams, and you don't see yourself buying into that "jock" culture, then you might just have to look elsewhere.
