Just got this guitar today, it wasn't even setup. I had to re-string it with .12-60 gauge strings. I re-strung it and waited a couple hours. The neck is bowed back just a bit. Anyway the problem is the 6th, 5th, and 4th strings are buzzing when I fret anything towards the body of the guitar. I just finished adjusting the intonation to perfection, but it is still buzzing. Earlier it was buzzing really bad. I am looking for any possible solutions to fix this. Thanks.
You're gonna have to tighten the truss rod. The guitar probably was set up for much thinner strings, and the strings are going too far of a distance to get to the frets with the way the neck is right now. So yeah, tighten the truss rod, and I'm confident you'll be good to go
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Let the neck settle for a day. Then adjust it if is still bowed. You may have you repeat this a few times after making a big change in string gauge.
Yah, I did make a huge change in string gauge. I am pretty sure it came with .10's or .9's and I put on 12-56. I even had to file down the saddles and the nut. I just gave the truss rod a slight turn to tighten it. I am going to let it sit for an hour or two. Or even all night, and see how it is tomorrow.

I do not get, how is possible, that with much BIGGER TENSION strings you get a back bowed neck and fret buzz until you downtune a lot from normal tuning? That is not logical, the neck should be bowed, because of a big tension of the strings. You should be probably able to have a bit lower action because of that high tension.

If you downtune, the truss rod setup should do the job. Relief should be about 0,1 - 0,3 mm between the 1st and cca. 17th fret. Let us know, what was the problem.
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