GP-100 44 special problem

Purchased a new GP100 in 44 special. Shot Winchester cowboy load and it shot about 14 inches high. Adjusted the sight and got the point of impact to drop.
No malfunction with the Winchester loads, I than attempted to shoot factory Federal lead hollow points and the cylinder was binding up and would not rotate. I again used the factory Winchester with no problem. Has anyone had any similar problems.

Welcome to the Forum.
W/o inspecting it,, I'd offer a little advice. First, clean under the ejector star carefully. Sometimes just a little crud under there allows a slightly raised star. And different brass or ammo can have slightly different dimensions. Combine the two, and you may have your problem.
Next, look at the brass & bullet closely & see if the Federal is seating as deeply in the chambers. Sometimes the bullet profile of different ammo can prevent ammo from seating, as can the slightly different length of brass. A set of calipers can come in handy in checking the length of brass. Measure the thickness of the case rim, and the OAL of the cases too.

Just a few ideas.

Check under the extractor star. Clean with a brush and solvent. My 44 GP did the same thing. WW cowboy ammo is dirty. Bob!!

Thanks. I cleaned it good still doing the same thing. Will send back to factory.