I have a duo fast SureShot 764 nail gun that won't depressurize after a shot is fired and the driver stays stuck out?

You may need to rebuilt or send it off to be rebuilt.
Here is a link to rebuild kit.
Copy and paste

https://www.rebuild-kits.com/rebuild-duo-fast-lfn-764/



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check this but scan for virus too
Mastercraft sureshot stapler manual

also email the ompany for one:
http://www.canadiantire.ca/en/pdp/mastercraft-sure-shot-heavy-duty-staple-nail-gun-0577916p.html

you would have to get ahold of duo-fast directly here is there site Duo Fast Request Info fill out the form to request a manual for your type of nailer

If the trigger is set to single fire, you will need to place the gun against the work then pull trigger as you have done. Try setting the trigger to bump fire and try again. If hear a thump inside the gun, remove the head and check that the head valve in not stuck from lack of lubrication. Easy test, remove the nails, remove trigger pin, remove trigger and manually push trigger firing valve. If the gun fires then suspect faulty trigger or safety arm not lifting enought to activate the trigger valve. Good luck

As a safety precaution, nailers have incorporated a safety foot that will prevent the gun from firing unless you push down hard. Some guns also have a system where the gun will not fire at all if there are no nails in the gun. To dry fire this type of gun you must pull back the pusher or open the side door. If nails do not feed properly, check for wrong nails, bent rails or weak pusher spring. If all is good with rails and pusher, suspect that the driver/piston is not at top of cylinder and lower part of driver blade is preventing nails from advancing. Remove airline and push the driver to top and retest. If driver is slipping down the cylinder under its own weight, replace oring. Good luck

First, check that you are using the proper nails. The FP602 needs Full Round Head nails with plastic collation. If you are using Clipped Head nails with the paper tape collation the angle of the nails not let the driver catch the next nail and drive it into your work.
If you have the correct nails, check the magazine to make sure the nails are feeding all the way up to the driver. If there is anything blocking the way or if the spring on the feeder isn't taught enough to pull the clip all the way up the driver won't be able to catch the next nail and drive it in.

Here are a few tests for you to try. You will need a piece of rubber or coiled up old hose.
First open side door and remove nails. Tilt gun head down then up again to check if piston is loose in the cylinder. The piston should stay in top position. If piston drops to bottom of cylinder remove head and replace piston oring or apply some layers of teflon tape under oring to expand oring slightly untill piston stays at top but still can be pushed down cylinder (look at the lower bumper to make sure that it is not cracked or missing pieces, if it is breaking up the pieces can lodge within the air path to the feeded piston). If driver piston now stays at top, connect air to gun and with side door open contact gun to rubber firing gun noticing the feeder movement. With very rapid firing of the gun, the feeder should move back and fourth just as fast as the driver moves. If the feeder seems to move slower than the driver moves then check/replace spring in feeder piston chamber. If spring seems strong enough in your opinion then problem is restriction in the air supply to feeder, if air path is clear then replace orings to feed piston. You will need to remove the two 6m allen screws at front of gun and split gun apart to check restriction at the oring sealing these two parts. Sometimes debris traped at oring (white oring) will restrict air to feeder. Good luck.

Your nailer is a very heavy duty nailer with very powerful blow. Works best with full size nails, not 2 inch range that are used in fencing, they are not spaced correctly for your gun (like hitting number 6 nail with sledge hammer). Open side door and remove the nails, leave the door open and dry fire gun against piece of rubber or old coiled air hose. The driver should return all the way up between shots and the feeder should move back then forward just as fast as the driver moves. If the feeder seems to move in slower motion then pull feed piston and replace orings and remove debris from feed cylinder. If the driver seems to stick out further than normal then lower bumper could be breaking up causing debris to enter feeder. Make sure that the driver is not bent and has a squared bottom, if rounded, remove and grind square. Finally adjust the depth control up or down slightly and bump fire for test, do not place gun on the work then fire. good luck

Open your gun remove the nail close your gun.

In our shop we have a lot of broken drivers to fit various nailers to use as driver punch.
So that the driver punch does not also get stuck, you must grind the side of steel to allow for wedged nail. Sometimes you must hit the punch very hard. It could crack the head, so if very stuck, remove head and cylinder parts and place body of gun against piece of wood. Not all guns can be saved. Also, hitting driver steel can eject pieces of metal, wear proper protective gear and secure area. After you free the driver, check surface of point for deformation. Good luck