Adjust depth on Porter Cable finish nailer?

I borrowed a friend's Porter Cable 2-1/2 inch, 15ga. finish nailer to install a window. It doesn't sink the nails far enough, even when I have the max air pressure set.
My friend says you can't do anything about that, but don't Porter Cable nailers usually have a depth adjustment? If so, where would it be and what does it look like? I haven't used one of these before, so any help would be appreciated.
If it doesn't have a depth adjustment, what else can I try? Could it not be sinking them because it hasn't been oiled in a while? Anything else I should check?
Thanks!

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Check for a small dial under the trigger or there about. Turn the dial to adjust. Test on scrap material.
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-- Oren
"I didn’t say it was your fault, I said I was blaming you."

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If you'll tell us the model number, we'll have a better chance of helping.

Steve wrote:
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The air pressure the OP is running would be nice to know as well, along with the materials being nailed.

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It's a Model FN250A, and even when I bump up the air pressure to 100-120, it still doesn't penetrate all the way through the pine window jamb into a 2x6.

DK wrote:
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You could try spraying the clip of nails with silicone before putting them in the magazine. Might leave some residue on the lumber though.

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Here's a link to a page with photos. The adjustment for the depth is specifically pointed out.     http://www.newwoodworker.com/reviews/pcfnnailer.html I have the FN250B, so there shouldn't be much difference.
Possible reasons for your issue: * If you don't hold the gun against the surface firmly, the recoil will cause it to kick back, leaving the nail partly driven. This gets worse with higher pressure and harder wood. Practice on some scrap pieces to improve your technique. * The depth adjustment mechanism isn't seated properly. If it's "jumped the track" up or down from its proper position, the depth won't be right. The wheel just moves the safety shoe up and down, so check for that. * You ARE using 16-gauge nails, aren't you? That's the only size that will work right. * Open the front and check for jams. Debris might be stuck in there.
Other things you can't do much about: * It's actually broken. To the repair shop it goes. * The internal rubber seals are worn out, letting the air leak past instead of pushing the nail. You're supposed to add 6 drops of oil each day it's used, but if it sits too long, the rubber might dry out anyway. * There's metal between the sill and the 2x6, or you're hitting a nail or screw.
What kind of wood are you nailing? Is it really hard? I've used mine successfully on mesquite, which is pretty darn hard. On the other hand, I've seen nails just bounce off of knots. That's why you're supposed to wear eye protection.
Good luck. Let us know what you figure out.

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Most nailers have a small wheel adjustment. Make sure you put a drop of oil into the intake before use (use the recommended oil), check for proper air pressure, and run a few test shots.