My floor is done now I'm working on the trim. I purchased a 15 gauge nailer to attach the first and last pieces of floor closest to the wall which worked really slick. I'm installing window trim and i'm not sure the 15 gauge nailer is the right tool i'm thinking the nailer will split the window casing if i nail into it. What size do you guys use? 23 gauge pin nailer? 18 gauge brad nailer? I'm also concerned about the nail head size when filling.

23 ga. is great when you can get away with it, like thin or delicate trim. or maybe shooting pins at the frame corners( wood to wood ). I would think window trim would take the 18 ga. . Different 18 ga nailers leave different size holes. I love my cheapo Harbor Freight nailer, for baseboards. 20 bucks, it's been going for a couple years ( for 20 bucks I have a backup in the truck ), . It leaves a lot smaller hole than my 18 ga Bostitch. Run some tape over the tip, so it doesn't dent the wood.

Your 15 gauge pneumatic finish nailer should work fine for casing out windows. If you're using MDF trim, finish nailers tend to mushroom the holes a little, so watch for that. Pine works much better. That gauge should not split the trim unless you nail too close to the mitered cuts. What I do is use a brad nailer with skinny but long brads to nail the thin side of the casing to the jamb. Then I use the thicker 15 gauge to nail the other thick side of the casing on the wall side. I find this works better but you do not have to do it this way. Just don't nail too close to the ends or edges of the trim and you should be fine.

guys thanks for the response, i'm shooting into 1/2 red oak ranch casing. Gary i like your idea i'll use my 15 gauge bostich for the thick part and get a smaller one for the thin side. Have you tried using headless nails for this or just your 18 gauge?

IMO 23 gauge is not sufficient for the "thin side",( I would use 18).
I'm not sure if Gary was referring to using the 16 ga on oak. It obviously will leave a larger hole, but will have good holding power, and the hole can be hidden.

k thanks for the tip i'll swing by harbor freight on the way home tomorrow.

i bought a 18 gauge nailer that accepts 3/8th to 2 inch brads. I also purchased 1 inch brads but these seem to long. I'm gong to use 2 inch on the thick side of the casing. What do you guys think for the thin side of the casing should i drop down to a 1/2 inch brad?

A good rule of thumb is the fastener should be a minimum of twice the thickness of the wood that your nailing through. Except of coarse if your going through something like drywall first before you hit wood. then obviously you would add the drywall thickness.

So in answer to your question...if the thin part of the casing is 1/4", then 1/2" fasteners would be fine. Assuming that you are anchoring directly into the wood portion of the frame, under the casing.

thanks for the lesson, the brads will be going into the casing.