Where can I find a driver blade guide and driver blade seal for a Hilti RN312 framing nail gun?

A nailer will misfire if the next nail cannot advance to proper position. Make sure that the nails move freely in the rails. If the nails move freely then most likely the piston driver is not moving back up all the way to top of cylinder. This can happen if the piston oring is too loose or too tight. The piston oring should hold the piston in place without dropping down the cylinder. Also not so tight that there is too much friction. If the piston seems correct then check for debris in the head causing restriction of the discharge air. Remove the head valve to make sure all parts are ok. If headvalve and discharge port seems ok then air must be leaking past the nose of the gun. Under the bumper is a metal washer that helps to prevent too much air from leaking down the nose. You can make a good seal out of a piece of innertube to create more pressure for pushing the piston up. Cut a circle of rubber to fit under the bumper and on top of the metal washer, the bumper will hold it in place. Cut a slit or hole so that the piston driver will just fit snuggly. You should have solved the problem. Good luck with your repair.

If gun firing but nails not being driven could be one of two basic problems:
1. Nail jammed in magazine not allowing nails to move up.
Empty magazine, does follower move to top of magazine. Push gun against work piece, does fan motor start? Yes - jam in magazine or lock out bar not operating. (this would allow nail un to fire when out of nails)
2. Piston/driver not returning fully after firing, hence driver blade on top of next nail instead of behind it. This could again be caused by a jammed nail or just a nail head. Another case of not returning is the combustion chamber not making a good seal, check O rings on framer (they are steel rings on bradders) it may just need a good clean it is surprising how dirty they can get and if not cleaned a build up of dirt could break a seal. If not been cleaned for a long time worth checking piston rings, worst case scenario dirt builds up around the rings and stick fully in requiring new piston if the rings will not come out.
Nail guns work on the principle that an explosion pushes the piston driver forcing a nail into the work piece, after the explosion a vacuum is created and it is this that 'sucks' the piston/driver back up the cylinder.

Easy test, Remove the nails and remove the trigger retainer pin and trigger to expose the trigger valve (tva6 valve). With air connected and nails removed, quickly depress the trigger firing pin all the way in. Gun should fire (if gun fires, adjust safety foot to make better contact with tva6), if no joy air is leaking past orings in the head valve or head gasket vent hole and/or trigger valve. Remove head and check gasket around vent hold (small hole in the head gasket). If the gasket good remove head valve and examine surface where orings make contact for fine scratches. If scratched or worn, orings are not sealing. To check if orings are leaking, apply lots of white grease to orings in the head valve, replace the head and test fire. If the gun fires, sand contact areas with fine sandpaper and or use oversize orings or wind teflon tape under the external orings. The metal ring or washer that you are wondering about is sometimes used to space up the bumper to control depth of nail. Other nailers use a metal fitting under the bumper to help guide the driver and to seal the lower chamber helping to prevent too much air leaking past the driver. If too much air leaks past the driver, guide, the piston may not return to top. Good luck

Special order only and they are expensive. We used to sell the Spotnails MNS5 which was the same tool as the Hilti. All we have left are some 8 penny nails. We have inquired about more as Spotnails does not produce them anymore and the cost wasn't worth it. You will be better off to buy a newer gun that shoots a more common nail.

Miss fire usually occurs when piston/driver is bent, piston oring worn, lower bumper cracked or missing pieces or upper bumper is cracked. Easy to check. Remove head and pull piston. If bent try to adjust, but be careful, blade breaks easily. Piston should fit snugly in cylinder, if loose, replace piston oring. If oring/plastic ring ok examine lower bumper for cracks and replace as needed. If lower bumper ok, pull out headvalve and examine upper bumper for cracks. If upper bumper ok, pull cylinder and look for loose check band around cylinder. Check band is black rubber and should be placed around cylinder fitting snuggly covering series of holes. Replace parts as needed and lube with silicone paste sold at Lowes in the plumbing department (or white grease). Good luck

The feed pawl is moved by a piston that extends from a cylinder on the lower side of the guide body. There are a couple seals inside the cylinder that if damaged will not hold enough air to activate the piston and advance the next nail. The two seals are Senco part number LB0828 & LB0845. Better yet get a Senco YK0369 repair kit and replace all of your o-rings, you'll have a like new gun for around $60.

Driver not returning is usually caused by bent driver, worn lower bumper, loose piston oring and/or loose or broken check seal. Remove nails from magazine and push driver to top position; lightly tap nose of gun against rubber mat or soft wood. Driver should remain at top. If driver slides down, replace piston oring. If driver stays up remove head and pull out cylinder. Examine driver for bend, check lower bumper for missing pieces and look for check seal inplace around outside of cylinder. The check seal covers a row of holes in cylinder and could be oring or rubber band. It should fit snuggly around cylinder. Replace parts as needed. If all parts look good, examine upper bumper for cracks or missing pieces. It is located in the headvalve and is usually made of vinyl. When installing piston, check that it does not fit too tightly in cylinder. You should be able to push it down cylinder rather easily and stay in positon without dropping under its own weight. Lube all orings with silicone paste (sold at lowes in the plumbing or swimming pool departments). Good holidays

Causes of piston not retracting are as follows. Cracked /worn bumper, if cracked air will leak between piston and bumper. Try test, remove nails and dry fire gun against rubber or soft wood; depress trigger push gun against wood/rubber and hold in this position. Piston should stay down and no air should leak past nose. Worn piston oring, piston should not slide down cylinder under its own weight. Loose or missing check seal, remove cylinder and look for black rubber band around series of holes. Band should be in place and fit snuggly. Good luck

Many causes for this problem. Some things to check. Push the driver up by hand to see if it moves easily /hard. If hard, check for bent driver or dry cylinder. If it moves easily, check piston oring too worn and /or air could be leaking down past the bumper area. Most guns have very close fitting bumper or a seal below bumper. If too much air leaks down past bumper driver will not return fully. Check seal could be loose or broken. Remove cylinder and look for check seal covering a row of holes on outer/mid to lower part of cylinder. could be a band or oring and should fit rather tight. If ok only other parts to check are the headvalve and piston stop. Piston stop should not have cracks or missing pieces (piston stop slows/stops piston when it returns to top). Head valve should be well lubed. Good luck

The company below sells a full line of nails for your gun. The rn312 uses 17 degree nails and can be ordered from www.spotnails.com. Good luck with your nailing projects.