FN finish nailer FN250b firing issue

[Rmizikar]

The nailer fires a nail about 85% of the time. Sometimes when the trigger is pulled nothing happens. There is no tension on the trigger. After I replace the nose of the and fire it several times , it will fire another nail. Any idea what is causing this?

[xr7-390]

i know this simple but check that the nails are sliding in proper groove for the nails because if not that will cause what your saying , i know i did it myself the nail heads did not sit in the top slide