New strings are hard to play

Changing brands typically does not change how hard it is to fret the strings. Is it just harder to press or is it that your fingers are sliding or something?

And, are you sure all of the strings are the same size as the originals? Some special sets have different sizes than other sets.

Is this the first time you've changed the strings in the 5 months you've had the guitar? If so could just be you don't know what new strings feel like yet

I find them harder to fret.

I'm not absolutely certain they're the same size as the old ones, but the store I got them at is the same store that sold me the guitar, so I would hope they'd be able to tell.

Even after 5 months you may notice some change but should not notice enough of a change to get your frustrated with the guitar.

I would take it back to them and have them check it out because if they went with a larger size string they could have thrown off the entire setup.

Actually, I've found the last few days that the more I play the easier it gets (to a certain extent, after about 3 or 4 hours my fingers start to hurt a bit).

So I guess I'm just gonna keep at it.

Thanks for the suggestions though.

Typically things sound better and seem easier to me after I change strings -- clearer tone, etc. I think Nils is right, you probably got a heavier gauge string this time around. I play with lights (.012 for the high e string to .053 for the low E). That seems to be a very popular gauge for acoustic.

on acoustics, lights are usually 11s, med lights are 12s and mediums are 13. they usually come set up with lights or medium lights.

0.12 strings on acoustic can be tough for the fingers.
Soon after that I bought my dreadnought I changed to 0.11 strings to make it easier for my lefthand fingers. Then I checked the action on the 12 fret and had it corrected to 6/64" (2,4 mm). This made it much easier to play!
Now, after a year of playing, my fingers are ready for 0.12 strings.

Get someone experienced player to do the job for you.He will know what is right for a beginner.

What do you mean you changed the action?

The action refers to the distance from the strings to the frets. If you go with ligheter strings that distance is increased, and just the opposite for heavier strings.

It could be the composition of the strings. Martin (like most companies) makes several different alloys - a 90/10 bronze will feel a little different from a 92/8 phosphor bronze.