Musket Lock Maintenance: Disassembly

Steve Blancard                                                                 

Ordnance Sergeant

3rd Regiment, ANV


Ok, be honest – have you every disassembled your musket’s lock for maintenance?  Been a long time…maybe never?  I suspect that most reenactors have never done it.  All good soldiers know how to clean their musket after a weekend of battle.  But after the bore is clean, dry and oiled and the outside is wiped down with an oily rag, the soldier’s best friend is often stood in a closet until the next event.  That’s all well and good.  But for a musket that is used routinely in the field, the lock should be removed and completely disassembled for cleaning, inspection and lubrication once a year.  This is because fouling, dirt and rust will accumulate inside the lock.  These contaminants mix with any lubrication that was there and turn to a grinding paste.  This can lead to excessive wear and an unsafe lock.  

While our muskets are modern reproductions, the basic lock design is over 250 years old.  These locks have proven to be rugged and dependable; however like all things mechanical, they need some maintenance from time to time.  In this article, we will go through the step by step disassembly of a Springfield Model 1863 lock.  While you may have another model, the basic design is the same and you should have no problem following along with your lock in hand.  We will also use the standard musket tools available to soldiers back in the day, and available from sutlers today.  Here is a musket lock with all the internal parts labeled, note the names and location of all the parts.

First off, the lock must be removed from the stock.  Some locks are a tight fit and need to be carefully coaxed out. 

Step #1 – Place the hammer in the half-cock position.  This does two things; it ensures the hammer nose will clear the cone as the lock is removed and prevents damage to the stock as the lock comes out.  More on this shortly. 

Step#2 – With a properly fitting musket wrench (screwdriver blade) unscrew both lock retaining screws on the left side about 2 turns, being sure to leave the screw threads partially engaged in the lock.  Now take a non-marring hammer or block of wood and gently tap on the screws alternately to push the lock part way out of the stock.  This will break the lock loose from a tight stock.  Remove the lock screws completely and remove the lock from the stock. 

With the lock in your hand, pull back the hammer slightly, press up on the sear and lower the hammer to the rest position.  Now look at the lock in the photo below.  Notice that at the bottom of the lock, the end of the mainspring attached to the stirrup hangs down below the bottom edge of the lock plate.  If you had tried to remove the lock with the hammer all the way down, that protruding piece would have dug into the stock as you removed the lock causing damage to the wood.   This is why it is so important to put the hammer at half cock before removing the lock.  Not all locks will dig into the wood, but originals and some reproductions will.

Step #3 – Put the hammer on full cock.  This compresses the mainspring.

Step #4 – Carefully install the mainspring vice on the spring as shown.  Don’t try to compress the spring any further, just install the vice and tighten the thumb screw until its snug.   A modern C-clamp can be used as a substitute for the original style tool, but it may not be as secure.

Step #6 – press up on the sear to release and lower the hammer to the rest position.  The mainspring vice will hold the spring compressed and the hammer and tumbler will now move freely.  Disengage the end of the spring from the stirrup.  There is an alignment pin in the spring near the “U” shaped bend that goes in a hole in the lock plate.  Now gently wiggle the spring and vice together back and forth, loosening the alignment pin. Carefully pull the spring off the lock plate as you wiggle it.  The spring will pull free.  Set the spring and vice aside, keeping the vice on the spring.

Step #7 – Using your musket tool screwdriver, loosen the sear spring screw about 1.5 turns only. 

 With the screw slightly loose, the sear spring which has a tab on the back that engages a slot in the lock plate, can now be pulled away from the slot and pulled up out of the way.

Now completely unscrew the sear spring screw and remove with the sear spring.

Step #8 – Unscrew the sear screw and remove the sear.

Step #9 – Unscrew and remove the last screw that holds the bridle in place. The bridle has an alignment pin on the back that goes into a hole in the lock plate. 

The bridle should just lift off, but if it has been a long time since it was removed, it may need a little gentle coaxing.

All that remains now is the tumbler.  The tumbler has a round-to-square shank that goes through a hole in the lock plate.  The hammer is a slight press fit on the square shank.

Step #9 – It’s time to remove the hammer.  First the hammer screw needs to be removed.

Step #10 – Place the lock between 2 pieces of solid wood, allowing the tumbler to hang down between them.  You will be tapping the tumbler out of the hammer (not pulling the hammer off the tumbler).  So the tumbler needs to be free to be driven out the bottom.  Your Tumbler and Wire punch will be used or other suitable sized punch.  On an original US army Tumbler and Wire punch, the larger of the two punches is the one to use here.  The diameter of the punch should be slightly smaller than the threads in the hole.  It is imperative that the punch used fit easily down inside the threaded hole without touching the threads.  It will seat in the bottom of the hole.  Now with your lock plate on the wooden blocks, straddling the tumbler and your punch in place, firmly tap the punch. 

It may take a few solid taps to dislodge the tumbler.  On original muskets there is a very slight taper to the square end of the tumbler.  This allows the hammer to fit snugly and the tumbler to be removed with little effort.  Italian repro muskets are not made to the same exacting standards and may not have the taper.  However, with a few sharp taps, the hammer and tumbler should separate.


The lock is now completely disassembled and ready for cleaning and inspection.  It wasn’t that hard now was it? 

Musket Lock Maintenance: Cleaning and Inspection

Now that your lock is broken down, it’s time to give it a good cleaning.  If it has been a few seasons or longer, there is likely to be a build-up of dirt, powder fouling and/or rust on some of the parts.  If there is any grease left on the tumbler, it has probably mixed with the dirt to form an abrasive compound that needs to be removed.  Clean all the parts in some hot soapy water and dry thoroughly.  If rust is still present, clean it off with some 0000 steel wool or if it is real bad, some 400 grits wet/dry sandpaper.  Once all your parts are clean and dry it time to give them a close inspection.  Inspect all the parts closely for wear, cracks or other damage.  Look especially close at the nose of the sear (the part that engages the half and full cock notches on the tumbler).  Both parts should be hardened, but generally the sear is a little softer than the tumbler. The sear tip should have a crisp, flat edge that engages the tumbler.  If it looks worn, rounded or damaged, replace the sear.  Below are two photos that show the interaction of the sear and tumbler at both the half and full cock positions (bridle removed for clarity).


Look closely at the half and full cock notches on the tumbler.  They should be sharp and crisp as well.   The full cock notch is flat which allows the sear to be pulled off it when the trigger is pulled.  Sharp, crisp edges on the sear ensure that it will not slip off full cock accidently.  The same goes for the full cock notch on the tumbler.  In the half cock position, the sear nose fits in the half cock notch.  The lip of the notch keeps the sear from disengaging if the trigger is pulled.  If that lip is chipped or broken, the musket is not safe to use and the tumbler must be replaced.  The fitting and condition of these two pieces are critical to the safety of the musket. 

The mainsprings on most Italian made muskets are made from cast steel, not forged steel as the originals were.  Casting is a more efficient (read cheaper) way to produce large flat springs.  However, cast springs are more prone to breakage than a forged spring.  Look for small cracks around the “U” bend of the spring.  Sear springs are made of sheet spring steel and are usually pretty reliable.  But it’s a good idea to keep a spare main and sear spring in your kit, just in case. 

How was the fit of the hammer onto the square shank of the tumbler?  If it was snug with no slop, that’s good.  If the hammer was loose on the tumbler, then there is a problem.  If this is the case, the best thing to do is order a new tumbler and hammer together, and replace them as a pair.  In a pinch, there are ways to tighten up this slop, but this is beyond the scope of this article.

Another thing to look at is the clearance between the tumbler and the bridle.  Insert the tumbler into the lock plate, then attach the bridle with the bridle screw, sear and sear screw, no need for the sear spring at this point. 

A note on sear screws - on original Springfield sear screws the threads end at an exact location on the screw shank.  There is a very good reason for this.  As the screw is tightened, the end of the threads stop the screw from turning in beyond a predetermined point.  Without this precise thread end point, the screw can be over tightened, pulling the bridle down against the sear, pinching it between the bridle and lock plate.  Unfortunately, most Italian manufacturers are casual in the threading of this screw, which results in too much thread, allowing the screw to go in too far, pinching the sear.  I have seen many reproduction musket locks with the sear screw either over tightened or intentionally left loose, neither of which is desirable or safe.  Later on, I’ll discuss how to resolve this problem.

With the above note in mind, gently tighten the sear screw until the screw head just snugs up against the bridle – then stop.  With the 2 screws snug, verify that the tumbler and sear rotate freely with no binding.  If it binds, there is a problem that needs to be fixed.  Usually, these parts are properly matched at the factory, but not always.  One of our members had a musket with a tumbler that did not have proper clearance and it caused the musket’s hammer to freeze up when firing.  I ended up having to remove about .020” from the underside of the bridle in order for it to have proper clearance.  It has been working fine ever since.

All your lock parts should now be in good condition, clean, free of rust and ready to go back together.

Musket Lock Maintenance – Part 3: Lubrication and Assembly       

With all your parts cleaned and inspected, it’s time to lubricate and assemble the lock.  In days of old they may have used whale oil or axle grease.  Today, the best choice is white lithium grease.  You can pick up a tube of it at a NAPA auto parts store for under $3.00.  

Step #1 - Apply a little grease around the tumbler hole in the lock plate and the round part of the tumbler’s shaft.  Insert tumbler into lock plate.

Step #2 – Take a small block of wood and drill a 3/8’ hole in it.  Holding the tumbler in the lock plate, turn the lock facing up and place it on the block.  Allow the small nub on the tumbler to set in the hole you drilled.  You now have the lock on a solid surface with tumbler supported, ready to install the hammer. 

Step # 3 – Install the hammer.  Note that there are four possible positions that the hammer can be installed on the tumbler.  Refer to the previous photos to ensure you mount it in the correct position.  The hammer should press part way onto the square shaft. 

At this point it’s a good idea to have a friend hold the lock plate in place while you tap the hammer down on the tumbler.  Use a wooden dowel or block of wood and tap it down firmly onto the tumbler. 

The hammer should go down almost flush with the top of the threaded hole.  There needs to be a little clearance between the back side of the hammer and lock plate, so the hammer/tumbler set rotates freely on the lock plate.  Now install the hammer screw.  The screw should not be used to pull the hammer down further onto the tumbler. It is simply there to keep the hammer from coming off the tumbler.  Attempting to pull the hammer down with the screw could cause the screw to break off.  Not a good thing.

Step #4 – Put a little lithium grease on the exposed side of the tumbler. 

Step # 5 – Install the bridle in place over the tumbler.  Be sure the alignment pin goes in the correct hole in the lock plate.  Install the bridle screw.  Again, check to make sure the tumbler/hammer rotate smoothly.

Step #6 – Installing the sear screw.  Earlier I discussed the precise end point of the threads on original Springfield sear screws, and how the Italian made screws are not so exacting.  With the Italian made screws, it is very easy to over tighten the sear screw causing the sear to bind, and the lock to be unsafe because the sear may not properly engage the half or full cock notches.  The good news is that there is an easy way to resolve this.  We will turn to modern technology and use a drop of liquid chemical thread locker.  The most common and readily available product is “Loctite”.  It comes in several different versions, but you want the medium strength “Threadlocker Blue 242”.  This can be found at almost any auto parts store or places like Walmart where they sell glue.  If your lock has a screw that stops without pulling down the bridle, disregard this.  But otherwise, I recommend the Loctite.

Be sure the sear screw threads are clean and completely free of oil or grease, the same goes for its threaded hole too.  Use a little alcohol or lacquer thinner and Q-tips to clean the hole and threads.  This is important for the Loctite to work properly.  Now put a small drop of Loctite in the sear screw threaded hole in the lock plate.  Then put a little lithium grease on the smooth shank of the sear screw (don’t get any on the threads) and sides of the sear around the sear’s hole.  Slip the sear into place under the bridle, insert the sear screw and tighten it just until the head of the screw is against the bridle, no further.  Again, make sure the tumbler rotates freely.  If all is well, wipe off any excess Loctite and set the lock aside for about 30 minutes to allow the Loctite to set.  Now your sear screw will be set in place.  If you used the #242 blue threadlocker, the screw can still be removed with a screwdriver. 

Step #7 – Install the sear spring and screw.  This is pretty much just the reverse of how you removed it.  Insert the screw into the loop on the spring and with the spring up out of the way, thread the screw into the lock plate.  Stop about 1.5 turns before it is tight. 

Press the spring down into place against the top of the sear, slightly compressing the spring as it bears against it.  Ensure the little tab on back of the spring slips into its slot, then while holding the spring in place, finish tightening the screw.


Step #8 – Install the mainspring.  You do still have it held in a compressed state by the spring vise – right?  Look closely at the lock plate where the spring goes. Are there any wear marks from the spring moving up and down?  Smear a little lithium grease on the lock plate over the wear marks.  Lower the hammer to the rest position.  This will put the stirrup at its lowest position, making it easy to hook the end of the main spring onto it. 

With the spring hooked to the stirrup, position the mainspring alignment pin into the alignment hole in the lock plate and press the main spring firmly onto the lock plate.  Next, bring the hammer back to full cock.  This will allow the tumbler and stirrup to take the load of the mainspring off the spring vise.  Now unscrew the spring vise and remove it.

The lock is now completely assembled.  Test it out by cycling the lock though all its positions.  Make sure it holds on half cock when the sear is pressed and that it holds on full cock and only releases when the sear is pressed. 

If you have followed this guidance and serviced your lock, you’ve probably found that it’s not as hard as it sounds.  With a few tools and a little attention to detail, it takes less than an hour to complete the entire lock service.  You’ll have the peace of mind not only knowing that it’s clean and properly lubricated, but how the lock actually works.  As mentioned earlier, the basic lock design is over 250 years old.  I can’t help but marvel and admire the ingenuity and craftsmanship of arms manufacturers from before the American Revolution. 

Hopefully this has given you the insight and confidence to provide your musket with the service it deserves.