Makita AF503 Brad Nailer won't fire nail

The nose tip is most likely stuck in the ready to fire position from too much force being applied when nailing. These guns are small and sensitive to forces being applied. Try bumping it to see if the nose tip is retracting and compressing with each bump. Unplug and unload the gun before trying to pull the tip of the nose to retract if it is stuck. Check for foreign objects obstructing the trigger and safety mechanism

Your nailer uses 18 guage straight nails, from 5/8" to 2" long. As long as you meet these requirements it doesn't matter if they are basic bright, galvanized or staniless nails. If you Google or Bing search "18 guage stainless steel nails" you will find several mail order places that carry the nails you need. Not very many places carry stainless steel nails in stock because of their cost. Unless you live in an area where their use is predominant you will have to order them.

This isn't actually answering your question, but I couldn't figure out how to just post a question.
I have Bostitch BT200. For probably 15 years. Haven't used it much. Mostly used nails abou 1 1/4 inches. But recent project needed 5/8 inch. It will fire 1 fine. But won't fire another unless I pull the magazine open and push it in. Then it will fire 1 only. Have to open and close magazine every time to fire 1 single nail. It fires longer brads fine. What can I do?

Nailers that use strips of nails (one nail directly behind the other) will sometimes drive two nails at once and is caused by damage to the driver. The nails are so close together that the driver will hit the first and part of the second nail head. Coil nailers, as your an451, use nails seperated by welded wire making it very difficult the the driver to hit the second nail. Usually when a coil nailer shoots two nails, it is acutally the trigger valve that acutates twice (two very rapid fires). Two very rapid fires is caused by faulty trigger valve. I have seen a roofing coil nailer fire one nail and a second nail drops out of the gun. Caused by weak / malfunction of nail feeder or wire used to weld nails together is too thick.

I would try different brads for it, dont use anything generic, sometimes the glue that bonds the brads will jam up gun

sometimes the parts jam up. make sure your properly oiling your air gun.

Go to this LINK and find the part/diagram that can help you.

Please thumbs or post back,thanks

The dent in the wood is not caused by the air. It's caused by the set that drives the brad. Are you oiling it consistenly? Are the brads the right manufacturer for your porter cable brad nailer? From the information you give it appears that the brads are not advancing correctly or that the air pressure is not sufficient to dislodge the brad from the brad strip on the first strike - it takes an additional strike to break it free. The standard for adding oil is to add ten drops of air tool oil for every hour of operation. That seems like a lot, but the correct amount of oil is a sure way to prevent most air tool problems.

is that a model AF505? if it is, your problem may be the gauge. make sure you use 18 gauge nails, he 16 gauge are too big and will jam in the gun.

A good-quality starter set, including both a compressor and a small nail gun, can be bought for around 200 US dollars (USD). More sophisticated models can reach 1000 USD or more. Optional features such as a hard-shell case, safety trigger, and depth adjustment can drive the price even higher. For one-time jobs, a nail gun can also be rented at hardware stores and home repair centers.