Hi, Johnny!
I am not talking best action here but talking the action which might be suitable for your barre practice. I always keep my guitar's action very low. And I was interested in how much we can lower the action. I've read very interesting site which was wrote by Japanese classical guitar teacher. He always sets up his new students nuts and saddles. Especially he lowers ladies saddle and nuts as low as making buzz. All of his female students new guitars have buzz. I thought that might be fantastic idea. New students, new guitars and buzz. This guitar (see the photo below) is Martin Backpacker. This one is my latest guitar and I like it very much. I bought this one a couple of months ago. I bought three pieces of nuts (see the photo below) for this guitar. They are the left three pieces. And I've sand one of them. You can see how much I've sanded bottom. It is more than 5 mm. And the (Martin's) original one (the left one) is almost the same as spare ones. I've sanded bottom, and nut slots are intact. Sanding bottom and sides are far easier than handle nut slots, because we can see it. I only use sand papers for set up nut and saddle for this guitar. I have already set up many guitars before but I have never lowered as much as making buzz before. But this time my mission was to make buzz.
I've got successfully buzz this time. But guitar's neck bends by string tension. After I strung all of them, the buzz disappear. This is important point too. Even if we've got buzz, it may disappear afterwards. We can get spare nuts and saddles in the internet very easily. The width is most important dimension of nut. If your ukulele is 37mm nut. Look for 37mm nuts. If you have spare ones and your original one intact, you can test actions as much as you want by yourself. And you can decide the best action, which includes as low as making buzz, for your barre practice by yourself. All of my guitar's nuts are not glued.
In usual, nuts are easy to remove by hand. But the nut in this Martin Backpacker was glued very tight. The photo shows wood tips on the bottom of the nut. I have never seen this wood tips before. I actually could not remove this nut and I brought it to repair shop. He tried it with wood piece and hammer first but he could not. Then he used pliers first to loosen the nut and used wood piece and hammer.
The way to check the nut height is as follows. We need to understand the figures below. The top figure is cape on 2nd fret and I pushed 5th fret. You can easily imagine that 3rd fret wire is contacted (I wrote "almost contact" in the figure though). Same thing happens on the bottom figure. The first fret wire can be contacted. My guitars have
contacts on they are all ok and no buzz. Zero fret may help your under standing (green arrow in the figure). This is actually same as nut itself.
We are not talking best set up. We just talking better set up for barre practice. My Martin Backpacker's 12th action is shown below. It is as low as the 1st string of Electric guitar (circle red right). It should be the 6th string of Acoustic guitar (circle right). It has no buzz.
