I can remove the air supply and look down the barrel and see the plunger partly engaged and interfering with the next nail. It comes with instructions, all needed o-rings and lubricant. One of the smallest nailers in the industry that is best suited for clamping actions or light fastening is PORTER-CABLE PIN138 23-Gauge 1-3/8 Inches Pin Nailer. I recently had a similar problem with my Porter Cable roofing gun. Porter-Cable 18-Gauge Pneumatic Brad Nailer Kit Hardwood Floor Nail Gun Air Tool 5 out of 5 stars (49) 49 product ratings - Porter-Cable 18-Gauge Pneumatic Brad Nailer Kit Hardwood Floor Nail Gun Air Tool It sounds like an o-ring. The gaskets failed on my Porter Cable pneumatic 18 gauge nail gun. Welcome to Just Answer. And I have to say it was pretty easy to do. The plunger which strikes the nail does not retract all that way and interferes with the next nail. I went on EBAY and found a complete Porter Cable o-ring overhaul kit for about $15.00. Porter-Cable BN200SB instruction manual and user guide 18 Gauge Pneumatic Brad Nailer BN200SB204460873 PORTER-CABLE PIN138 23-Gauge 1-3/8-Inch Pin Nailer. Sorry to hear about your problem. C. Porter Cable Pin Nailer Review 1. Unlike the large nailiing guns PIN138 resolves the problem of splitting while fastening materials. Hey guys, My framing nail gun is about 12 years old.