Jobs are very "professional" but we all know that behind a manager/ HR representant/ CEO/ etc, there's a human being which (to a certain extent) will be influenced by his human side when doing his job/ taking a job related decision.

Given the above, I wanted TRPs thoughts on asking a raise. The thing is that I don't wanna fail.

Context: been 4 months at a company; I worked my way around the social groups here and found out that I'm 16% underpaid compared to the lowest paid employee here. On the other side of the spectrum, a guy that's been here for ~ 3 years is paid double what I'm earning. -> hence, I can ask for a raise.

Initial discussions (1 month ago) resulted in HR telling me that I must prove that I'm working at the same level with the rest, have the same responsibility as the rest and do just as well as them and in this case they will "adjust me to the next payment bracket".

It's been 1 month and I got some shit done around here and I'm feeling confident I'll get even more done (am in line with the others).

I wanna take another shot at asking for a 15% raise. The thing is that asking for a raise is like asking your mom for money when you're young: do it wrongly and be a brat and you won't get a dime; do it correctly and you may even get more than you expected!

Some very important info: I can only talk to HR on the phone (the HR department is in a town 600 km away) and if I convince them that I'm good, they'll talk to the local manager to see what opinion he has about me and if he approves of the raise. I'd say I'm neutral with the guy: we did a few lunches together, had some work-related and non-work-related chat and he didn't seem neither delighted nor disgusted by me. He's pretty busy so I can't really call him for a cup of Joe daily.

So what are your thoughts on this TRP?

Edit:

more info on the matter:

-I'm ~15% paid less than the smallest salary here;

-I'm ~30% paid less than most people here;

-I'm ~100% paid less than the highest paid people here;

-I wasn't aware of this info when I got hired. It is a move upwards but I still feel like the biggest loser here.

-When I discussed with HR 1 month ago, they suggested that I spend at least 2 more weeks to get a feel of things before resuming this discussion.

Edit2:

Thank you to everyone who took their time to answer here and talk to me; I tried to reply to each and every one of your comments since you replied to my post. The vast majority decided on one of two things:

1). state clearly that this is not fair and shit has to change now (and branch swing if it doesn't soon enough);

2). start searching for a better offer and then confront them with it to leverage a raise or straight up branch swing to a better place.

Given these two, I'm starting to think about the swing. With this opportunity I want to ask: what do you guys think about America? Is it worth it to come there for a job? Generally speaking are salaries good (I'm not a heavy spender; presuming that I just eat and go out just 2-3 times a week in which I buy 2-3 beers, how much of my salary would I be left with? What's the average salary all around and let's work with that?) , are there enough jobs to go around?

If this is too OT, I will make a new post about the matter. Thanks once again.