Only shoots out one nail for every 4 or 5 trigger pulls

if you mean it only shoots air when you pull trigger and not a nail , disconect from air supply and open side of nail mag. (two screws on side) look for forign object in front towards head end , sometimes the paper that nails are wrapped in gets stuck in there , also there is a small spring metal clip at front of mag is this broken off and is unusually short ?

Most nailers have a two position setting on the trigger to allow for single fire or bump fire. If set on bump fire, the gun will work better when you bump fire the gun instead of placing the gun on the work then depress trigger. Bump fire works best when safety spring has good tension. Easy test. Make sure that the safety spring is in place (with air hose removed, contact foot should spring back quickly when pushed against work). With air connected, hold trigger and quickly bounce the gun against the work. If the gun does not fire when you bump, the trigger is most likely set to single fire. With trigger set to single fire, you must place the gun against the work, then depress trigger. If the gun shoots two nails while set to single fire, most likely worn trigger or worn out trigger valve. These parts are not expensive and are easy to replace. Good luck

Best practice is to bump fire the gun to prevent double fire. Do not place the gun on the work and pull the trigger. This takes practice while using at an angle. Works better if the nose piece has rather sharp points to help nose to stay in postion while you bump. With trigger depressed, practice without nails bumping/hitting wood at different angles untill you can bump hit at the spot that you need the fastener. If the gun double fires while bump-firing, most likely all the safety/trip parts are worn/loose. Not expensive to replace. Good luck.

Worn trigger and or worn firing valve. Remove the trigger and look for wear on contact surfaces (worn pin that holds trigger, worn inner lever inside trigger, worn or loose firing pin in valve ). Easy test for worn trigger. Remove the nails, remove trigger, fire the gun against wood with finger to test for proper action. If it works better without trigger, consider replacing trigger with new (I would also order the oring repair kit that includes the firing valve )

Try the other order, where you depress the gun first, and then pull the trigger.

Happened to me awhile back...just load few nails..it tends to shoot to many when you load it full. break a section in half load it and it should shoot just fine.

piston is probably jammed

This happens sometimes try holding it up against a board with the trigger depressed and then inset the battery.

The goal is to try to force the firing sequence to get the piston back to the right position with corded units this is simply done by attaching the air hose with the trigger pulled this causes air to rush into the gun chamber pushing the piston back and firing a nail out.

The cause of this is a misfire or jammed nail that stopped the piston in the wrong location so air will not build in the chamber correctly.

Hope that helps

the 601 had a design flaw, in the nose, where the nails hit as the are being pushed forward, the peice was made out of a peice of metal that was too soft, it wore down and that is where you get the double nail problem.

Senco offered a trade in, this was years ago, for a limited time and gave us credit towards new guns, which we gladly did

I hope this doesn't offend you. What I'm suggesting is that you may not be using your nail gun correctly. Some people keep the trigger pulled and bounce the gun onto the wood. This technique works okay, but placement accuracy of the nail suffers. The other technique is to place the gun on the wood and pull the trigger USING TWO HANDS! This is the technique suggested by the manufacturer. The problem with this technique is that if you apply insufficient pressure to the gun (USING ONE HAND) the safety is not engage so you don't shoot a nail. What usually happens - I just witnessed this a couple of weeks ago - is that not enough pressure is applied while pulling the trigger so you push harder and end up bumping the gun which shoots a nail - because you have the trigger pulled, but the nail shot was a surprise so it causes another bump (and is more apt to bounce because you're using just one hand). Because it is a machine and can operate faster than your reflexes - it shoots another nail. This happens before you can lift it off of the wood, or remove your finger from the trigger. That's the reason I keep the trigger pulled and bounce it. I know that after the bounce I've set a nail, and can remove my finger from the trigger. When I need to accurately set a nail I always use two hands, press hard and pull the trigger, and release quickly. Only pull the trigger when you know you're about to set a nail, and are poised above the workpiece.

new safeties on nailers have to push set safety than pull trigger no more just hold trigger and bump shoot nails