Apex Gunsmithing
27Feb/16

Detail Strip Guide: Lionheart LH9/Daewoo DP-51 & Variants

A while back I wrote a very basic text only guide for detail stripping the Lionheart LH9, a variant of the Daewoo DP-51 and its family of unique "triple action" pistols, but I never had the opportunity to make a proper guide with photos to match.  Today the LH9 gets a real guide as part of my ongoing series of detail strip posts to get caught back up!

The LH9 series of pistols is a premium version of the cult classic DP-51, which is itself a commercial variant of the South Korean service pistol, the K5.  Originally designed in the early to mid 80's as part of Korea's push for a domestically produced service pistol, the K5 was trialed to death over several years before final adoption in 1989/1990.  The history of Korean small arms and Daewoo/S&T Motiv is fascinating to read up on, I highly recommend the relevant chapters of Black Rifle which highlight US involvement in Korean small arms production during and after the Vietnam War.

On the homefront, the DP-51 was the victim of nebulous commercialization in the US, with numerous importers picking up batches of pistols including compact models and the relatively new .40S&W chambering christened the DH-40.  Between the model confusion, attempts to re-brand the pistols, and the sheer number of importers trying to pitch the gun as a new wonder-nine during the rise of the Clinton ban era, it's amazing that the DP-51 remains a cult hit and saw reintroduction in the US at all.  In 2011, the upstart Lionheart Industries turned the DP-51 into a premium hammer fired, alloy frame pistol with numerous features the US market demands in modern pistols.  The LH9 series maintains almost complete parts compatibility with the DP-51, and Lionheart provides a retail channel for parts to maintain both their LH9 and the original guns.

A plain black LH9N - "N" for Novaks sights.

A plain black LH9N - "N" for Novaks sights.

Field Strip

Field stripping the LH9 is as simple as it gets:

  1. Retract the slide partially, line up the slide lock cutout in the slide with the pivot of the slide stop then push the slide stop out right to left.
  2. Pull the slide forward and off the frame.
  3. Remove the recoil spring and guide rod.
  4. Lift out the barrel.
Basic field stripping

Basic field stripping

Slide Disassembly

  1. Drive out the firing pin retainer roll pin.  Direction doesn't really matter here but I like to be consistent and go left to right.  You can start this pin with an AR-15 3/32" bolt catch roll pin punch, and it shouldn't be overly tight.  This is the larger perpendicular pin in the middle of the slide serrations.
  2. Remove the firing pin and spring.  Pressing the firing pin block plunger in will free up the firing pin.  The spring may try to hide in the firing pin channel, so fish that out.

    The firing pin and block plunger.

    The firing pin and block plunger.

  3. Remove the firing pin block and spring.  These fall right out, and you may notice the spring is surprisingly light so not to add weight to the trigger pull.
  4. Drive out the extractor roll pin.  WARNING: this particular pin is very snug and quite small, the perfect combination for bent punches.  I would recommend a starter roll pin punch and a drive punch combination.  Again direction shouldn't matter for a roll pin, but bottom to top is the rule of thumb for vertical pins.  Best policy is to leave the extractor and its stubborn pin alone unless you absolutely need to remove it.

    This stubborn pin is not to be trifled with.  Caution!

    This stubborn pin is not to be trifled with. Caution!

  5. Remove the extractor and spring.

Slide Reassembly

There isn't much to this, just reverse order and drive the roll pins back in!  You'll need to push the firing pin in against its spring to drive the retainer pin in.

Frame Disassembly

  1. Remove the grip panels.  Note the rubber grommets on the grip screws.
  2. Remove the hammer spring.  Let the hammer fully down, then press on the spring cup on the bottom of the frame and push the pin out.  The spring tension isn't crazy here so you can do it by hand just fine!

    Conventional setup and may be compatible with some springs.

    Conventional setup and may be compatible with some springs.

  3. De-tension and remove the trigger bar spring.  Push the upper portion that lifts the trigger bar down and it will come out of its seat, then rotate the spring slightly and lift the bottom leg out of its hole in the frame.

    Trigger bar spring reminiscent of Berettas.

    Trigger bar spring reminiscent of Berettas.

  4. Remove the trigger bar.  Disengage the rear leg of the trigger spring from the peg of the trigger bar that it rests on, then lift the trigger bar out from the front and angle it out.

    Trigger bar levers out and lifts off.

    Trigger bar levers out and lifts off.

  5. (Optional) Remove the trigger and trigger spring.  These can be left in and not interfere with anything, but if you want to remove them just push out the headed trigger pin right to left.
  6. Disassemble the thumb safety.  Drive the tiny 1/16" roll pin part way from the top down and ensure it doesn't gouge the frame!  Carefully lift the front portion of the left hand lever up, making sure you don't let the spring and detent plunger take off.  The right hand lever will fall right out.
    This tiny roll pin connects the left side lever.

    This tiny roll pin connects the left side lever.

    Make sure this pin doesn't gouge your frame!

    Make sure this pin doesn't gouge your frame!

    Lift the front off of the tongue and groove, mind the spring!

    Lift the front off of the tongue and groove, mind the spring!

  7. Remove the hammer, strut and firing pin block lever.  The hammer pin is now exposed, and has a large head on the left side so push it out right to left.  The hammer strut can also be removed by pulling it straight out the top.

    Hammer, firing pin block lever and hammer strut.

    Hammer, firing pin block lever and hammer strut (should face backwards)

  8. Remove the sear and sear spring.  The small sear pin can be pushed out either direction, the sear and its spring will fall out.  Make note of the direction the sear spring sits and the notch in the sear for the bent leg of the spring.

    The single action sear and drop safety, note the spring and notch.

    The single action sear and drop safety, note the spring and notch.

  9. (Optional) Remove the magazine catch.  Pull the loop of the spring out of its hole in the frame and rotate the spring out, then pull it straight up to remove it.  The mag catch will fall out afterwards.  Note that you'll probably scratch the interior of the magwell with a hook trying to fish this spring out.

    Hook this spring and wrestle it out of its hole, scratching inevitable.

    Hook this spring and wrestle it out of its hole, scratching inevitable.

  10. (Optional) Remove the ejector.  It's retained by two small roll pins and generally there's no reason to remove it.

Frame Reassembly

Working backwards, beginning with the sear:

  1. Install the sear and spring.  Start by getting the sear in place and using the sear pin to keep the sear in place.  Squish the spring into its slot in the frame and finish pushing through the sear pin.

    Note the straight leg on bottom and the legs face the back of the frame.

    Note the straight leg on bottom and the legs face the back of the frame.

  2. Install the hammer components.  Drop the hammer strut in, ensuring the correct orientation with the top bent toward the rear.  Install the hammer with the firing pin lever on the right side of the hammer, then push the pin in.  Usually you'll have to shove the sear out of the way or the hammer will install in the cocked position, so let it back down if needed.
  3. Reassemble the thumb safety.  Drive the tiny roll pin out all the way before reassembly.  Angle the left side lever with spring and plunger down and drop it on the peg from the right side lever, then drive in the tiny pin from the top.
  4. (Optional) Install the trigger and spring.  If you removed the trigger and trigger spring, drop them back in and push the pin through.
  5. Install the trigger bar.  Drop in the bar and hook the peg into the trigger part way, then snag the trigger spring and seat it on the trigger bar peg to tension the trigger.  Keep the trigger fully forward to help position the trigger bar peg and make wrestling the spring much easier.
  6. Reinstall the trigger bar spring.  Hook the L shaped leg into the hole in the frame, rotate the spring into place and press the curved leg down under the trigger bar to seat it.
  7. Install the hammer spring and cup.  This was easy coming out, not so easy going back in.  Turn the frame upside down and cock the hammer, then insert the hammer spring and cup as a unit to make sure the strut aligns correctly with both of them.  Once everything is lined up, let the hammer down and press the spring up down.  If you've got everything aligned correctly (strut to hammer, strut through spring, spring seated in spring cup) then the spring tension will be reasonable and you can push the pin through.  If it's extremely heavy or the hammer can't operate normally, the hammer strut is likely misaligned.
  8. Put the grips back on and reassemble!
  9. Function check.  Check double and single action trigger function, triple action/DA+ function, trigger reset, safety function and slide lock on empty magazine.

Note: I don't recommend messing with the hammer assembly.  It consists of the physical hammer, the single action sear cog and the spring which powers it and is retained as a group by a bushing.  The spring is rather stout, so only mess with any of that if you absolutely have to due to sear damage.

 

Final Thoughts and Triple Action (DA+)

I wrote a short summary of how the triple action/DA+ mechanism works for my text guide, so for those curious I'll quote it here as well with some edits for clarity:

The hammer is composed of three major parts, plus a spring and plunger.  The hammer itself has no sear hooks like a 1911 or CZ does, instead there is a slice cut in the center of the hammer and a small cog inserted into it which has a single, centrally located sear surface.  The cog and hammer are held together by a bushing that rides on the hammer pin, so both parts rotate as a unit when the hammer is cocked manually.  The sear on the central cog catches on the actual spring loaded single action sear, and pulling the trigger pulls this spring loaded sear forward and drops the hammer.  The hammer body is what physically strikes the firing pin to fire the gun.

What happens when you push the hammer forward is that the hammer itself rotates but the cog in the middle doesn't.  It stays fixed in place, engaged to the sear, and the spring loaded plunger going over center provides the snap forward and back detent action.  When the trigger is pulled slightly the feet on the hammer are pulled forward by the trigger bar, causing the hammer body to once more go over center and flip rearward to cocked position.  The whole time, the actual sear system remains stationary.

There are built in safety mechanisms that work passively to prevent any sort of accidental discharge.  The same trigger bar motion that trips the sear also activates the firing pin block lever and deactivates the plunger, so the firing pin will always remain blocked without a full trigger pull.  On the sear itself there is a sizable shelf which acts as a drop safety, preventing any jar-off situations from allowing the hammer to fall fully in a similar manner to the half-cock or safety notch of a 1911.  If the trigger is not pulled fully the sear is not moved out of the way meaning the "feet" of the hammer will catch the shelf long before the hammer contacts the firing pin.

I've always liked the DP-51 design and the LH9 does an excellent job of bringing this cult classic back with most of the upgrades to turn it from an 80s wonder-nine into a modern duty pistol.  The Daewoo design is clever and offers several methods of carry due to its unique action including traditional hammer down double action with or without the thumb safety engaged, condition one "cocked and locked" carry with manual safety engaged, and the triple action/DA+ method with or without manual safety engaged.  The triple action mechanism can also be considered a decocker in a manner of speaking.

Thanks to Lionheart Industries for loaning the LH9N pistol pictured here to make this guide possible!

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