I've been experimenting with different loads of Unique for my 9mms, more specifically for my Kahr PM 9. The barrel is only about 2.75 inches, give or take a bit.

Factory Speer Lawman 115 gr yields 1,065 fps +- a bit in this Kahr. With 115 gr Berry RNRP plated I'm only getting 875+- fps using 4.2 gn Unique. OAL 1.035. This load does cycle reliably with less recoil than the factory round.

One resource, not the powder company, lists a max load of 6.1 gr Unique for 115 gr FMJ http://www.bing.com/search?q=m...19aa776425&FORM=QBLH.

Alliant's website lists a load of 6.3 gr Unique for jacketed. www.alliantpowder.com/reloader...derid=3&cartridge=23 Generally, I use lead loads for plated bullets and work up a bit if necessary and prudent.

With my load of 4.2 gr it seemed to fill up the case to the point where any more and I'd be compressing the powder. Does anyone have any experience with loading 9mm with Unique >4.2 gr and short barrel pistols?

I was able to get a pound of Bullseye recently, a slightly faster burning powder. Since it is a bit faster burning, I was speculating it might be better for short barreled pistols? Opinions?
I don't see how you can get 6.0+gr powder in a 9mm Luger case without compressing the powder.

Compressing Unique is not a problem.
Hornady JHP and 7.0gn Unique gave me 1275fps in my BHP. This is a max load in that pistol.
Nosler 115gn JHP and 6.1gn of Unique gave me 1260fps--max load.
Have loaded up to 6.0gn of Unique with a Penn 115gn L-SWC. My 9x19 1911 really likes the 6.0gn load.
Sierra 115gn JHP and 6.4gn of Unique gave 1312fps and slightly over 2" groups at 25 yards.
Start at the lowest starting load you can find and work up.
All pistol powders burn all they are going to within the first inch, so powder is not an issue with short or long barrels--it's all which powder your gun prefers. No matter the barrel length, the powder that produces the highest velocity at one barrel length will produce the highest velocity at any barrel length.
The accuracy of low pressure loads are almost always best with fast powders. As pressure go up, the most accurate powder move down the burn rate chart.

I use Unique because it works in just about everything but it is dirty. I prefer 700X because it burns so much cleaner. You might be happier with the Bullseye.

Seams the newer unique is a lot cleaner than the stuff from 15-20 years ago. I just finished up my old stash and now into this newer lot of 24 lbs. As long as you keep it on the upper end of pressure it seams to burn much cleaner for me. I shot 500 rounds through my 45 the other day and did not notice much difference than my W231 loads in cleanliness or accuracy.