Installing an Improved Sear Lever in the BHP
This tutorial covers the proper installation of the Cylinder & Slide Improved Sear Lever (Part # CS1950) for the Browning Hi-Power.

When it comes to Hi-Power work other than someone attempting to do a trigger job this is one of the most botched jobs that comes into the shop for corrective work.
While it is a pretty straight forward modification, you do need the proper equipment to get it right when you drill the new pivot pin hole for the sear lever. Ideally a milling machine is the preferred setup. A high quality drill press with indexing table could also be used. Trying to drill the hole by hand with a power drill or just in a vise with a drill press is going to lead to disaster.
So why would we be interested in installing an Improved Sear Lever? For the simple reason it gives us the ability to achieve a safe, reliable, lighter trigger pull below 5 pounds in conjunction with a trigger job on a Mark III Hi-Power. Without a trigger job it will typically reduce the factory trigger pull by about 2 to 2½ pounds.
What makes a Hi-Power a Mark III? Those pistols with the firing pin block system are Mark III’s and the Improved Sear Lever is specifically made for them. The Improved Sear Lever can be installed in a Mark II slide but requires altering in addition to removing the paddle and the slide needs to have additional machining done to allow the Improved Sear Lever to function properly.
Originally the Improved Sear Lever came into being with the Browning GP Hi-Power. The GP was Browning’s offering of a target grade Hi-Power. And compared to the standard Hi-Power the GP had some interesting features. To achieve a target weight trigger pull in a factory production pistol Browning modified several parts. Besides the Hammer and Sear they also modified the Sear Lever by moving the pivot point to give it more leverage.
But first before we get into installing an Improved Sear Lever a couple of things to note.
#1) The disclaimer. While I have personally installed well over a hundred Improved Sear Levers using this method and seen this method used to install many more, I have no control over how an individual may interpret these instructions, apply them or the type or quality of equipment being used. I have reviewed these instructions several times to ensure that they are accurate to the best of my knowledge and I believe properly detailed. So bottom line, don’t blame me if you screw up.
#2) A couple of caveat’s. If you install the Improved Sear Lever without a trigger job don’t be surprised if with the reduction in trigger pull weight you start to feel creep in your trigger pull. If you are doing a trigger job in conjunction with installing an Improved Sear Lever, you want to do the trigger job first before installing the Improved Sear Lever. In rare instances due to frame and slide dimensions being off you can end up with a pistol where you may not be able to get the trigger pull above 3 pounds without taking the Improved Sear Lever back out. I have probably had at least 20% of the MKIII trigger jobs that I’ve done where I didn’t use an Improved Sear Lever. I’m not going to go in-depth with the why’s and what-fore’s on this. It would be something that would be covered if I were to do a tutorial on trigger jobs for the Hi-Power.

Above are an Improved Sear Lever on top and a factory Sear Lever on bottom. Note the different locations of the pivot holes.

Here are some of the tools I will be using. The slide is completely disassembled except for the sights. Technically you could leave the extractor and firing pin assembly in but you are going to have chips everywhere inside the slide and the last thing you want is a failure because you couldn’t get them all cleaned out.
The tools are going to consist of:
- A small block of wood short enough to fit between the front and rear sight and about 1/2″ thick. This will be used as a spacer to help clamp the slide into the mill vise. It needs to be thick enough to protrude above the sights to protect them when the slide is clamped in the vise. I have mine made from Poplar and since it is soft it has formed itself to the radius and taper of the slide. If you are going to use a hard wood like oak then you will want to create a taper in the block to match the slide. What ever material you use you want to insure good contact and support along the length of the slide and vise.
- Pin Gage .094″ (I use a minus (-))
- Center Drill, #2
- Drill, 2.45mm (.0965″) (This usually comes with the Improved Sear Lever)
- Slave Pin .095″ (Not shown)
Setup

Here we have the slide in the mill vise. You can see the wood spacer block in position. The “chin” or spring tunnel of the slide is butted up against the vise jaw to add support. Use a small bubble level to level the slide in the vise. I leave the level on the slide, as shown in subsequent pictures, to use as an indicator. It will immediately show if for some reason the slide starts tipping in the vise as you are drilling the hole. I’ve never had a problem but its cheap insurance. If you do end up with a tipping slide then you need to review your setup.
When I drill my slides I drill them with the ejection port down as pictured. The reason for this is that it’s the port side of the slide where the sear lever pin has to fit the hole the tightest to keep from walking out. We are using a small drill and if you apply to much pressure when drilling you can cause it to bow or flex which will make it drill an enlarged hole, upwards of .004″ larger. So I’d rather have the enlarged side of the hole, if its going to happen, on the side where the pin doesn’t have to fit. It’s not something I’ve had happen, but I have seen it happen and you don’t want to go back and try to fix it.
A few other things with the equipment you use. First, make sure you are using a high quality drill chuck with basically “zero” run out. If you have a chuck with run out then you will have a tendency to drill an enlarged hole. Second, the mill vise. Ideally you want to be using an angle lock type. A regular vise will usually have a problem with the moveable jaw lifting as it is tightened which will cause the work to roll in the jaws. Which means you will be drilling a crooked hole.
Locating the New Hole

Now we need to locate where we are going to drill the new sear lever pin hole. Placing the .094″ Pin Gage in the drill chuck we will move the mill table until the Pin Gage aligns with the existing sear lever pin hole. The Pin Gage is about .002″ smaller than the hole so it will slip in without any interference once it is closely aligned with the hole. If you can see the pin flexing or can feel it clicking off the edge of the hole when you try and insert it into the hole then your not aligned close enough.
A word of advice on mill tables here. They will have a certain amount of free play or backlash. For that reason you always want to be moving in one direction. So you want to be moving the table to the Left when locating the sear lever pin hole and then from there you will keep moving to the Left to locate for the new hole. Make sure to lock the table down so you don’t accidentally bump it.
Once we are located on the existing hole we need to move the table to the new hole location. The instructions that come with the Improved Sear Lever specify the new hole at .250″ to the rear. Personally I locate my hole at .235″ as I think it gives the Improved Sear Lever a little better position with the sear. It’s up to you where you decide to drill the hole, it can be anywhere between those two numbers, you just don’t want to go over .250″. While the hole is not being moved up or down in the slide, if you have an error in hole location you would want the error to be towards the top of the slide and no more than .005″.
Drilling a Pilot Hole
Now that we have where the new pin hole is going to be located we will remove our locating pin and install a #2 Center Drill. The #2 Center Drill has a drill diameter of .080″ so it is smaller than the drill bit that we are using. We are going to drill a “pilot” hole for our 2.45mm drill bit, drilling the hole deep enough to where the center drill starts to lightly chamfer the drill hole. Clean away any metal chips around the hole and replace the Center Drill with the 2.45mm drill bit.
Drilling the Pivot Pin Hole
Now we will drill the pivot pin hole. I run my drill bit at 1100 rpm on the mill. Use cutting oil and keep the metal chips clear as you drill the hole. Back the bit out often to make sure the flutes stay clear of chips and don’t load up. Once you break through into the ejector slot in the slide the metal chips will tend to be trapped inside the slot.

Use light to moderate downward pressure to drill the hole. Remember we don’t want to flex the bit and cut an oversize hole. Watch for the bit to break through the other side of the slide. Once your through, your finished. Go ahead and remove the slide.
Deburr the Slide
If you have shop air handy blow the metal chips and oil off the slide or take a chip brush, etc. and clean the metal chips out. Don’t put too much effort into it right now since we still have some deburring to do before a thorough final cleaning.
As far as deburring the slide you want to put a light chamfer on the new hole removing any burrs. With the serrations it will be a little difficult but be careful since it will have a cosmetic impact on how the slide looks. Next remove any burrs from the inside of the slide where the drill bit came through in the sear lever and ejector slots. Now do a thorough cleanup of the slide.
Checking the Fit of the Improved Sear Lever
Now we will install just the Improved Sear Lever (no sear lever spring) into the slide using the .095″ slave pin. Sometimes the slave pin will be a tight fit and be difficult to push through the hole. I will either tap it in or take a #41 (.096″) drill bit and chase the hole by hand using a hand chuck to open it up. Your choice.

With the Improved Sear Lever installed using the slave pin we need to check the fit in the slide. We are looking for several things.
- The sear lever should have free movement up and down.
- The paddle of the sear lever should set all the way down on the ledges in the slide cut.
- The sear lever, highlighted by the arrow above, should ideally be flush or slightly (about .003″) below the center rail. If not then it shouldn’t protrude more than about .003″ above the center rail.
If everything checks out then we are finished with fitting. Of course that rarely happens so we may need to fit certain areas of the sear lever depending on what problems we identified from the list above.
Fitting of the Improved Sear Lever
I have listed below the most common problems and their appropriate fixes.
Correcting issues with fitting check #1- If the Improved Sear Lever does not have free movement then we need to find out where the interference is.
- The first area to check is to make sure that the paddle is not contacting the cut in the slide identified in the below picture with arrow “A”. If it is then taking a file you will want to move the radius on the paddle back to give it some clearance.
- Check to make sure the Improved Sear Lever spins freely on the slave pin. Usually this is not a problem at this point. (When you later install the Improved Sear Lever with the pivot pin there is the possibility of dinging the hole with the pin and closing it up which will cause it to not move freely.) If it does not spin freely then using a round needle file chase the hole to clean it up.
- Double check the sear lever slot in the slide to make sure you got the burrs removed originally when you deburred it after drilling the new hole.
- The most common cause is going to be from slight imperfections in the machining of the sear lever on the side highlighted by “C” in the picture below. Take a file and remove the imperfections making an even surface.

Correcting issues with fitting check #2- If the paddle won’t set down on the ledge in the slide then its usually one of these two reasons.
- Again the first area to check is to make sure that the paddle is not contacting the cut in the slide identified in the above picture with arrow “A”. If it is then taking a file you will want to move the radius on the paddle back to give it some clearance.
- Sometimes the slide is not cut correctly in area “B” shown in the picture above and you will end up with a lump down in the bottom of the cutout. This is a result of incomplete machining in the 2nd step of forming the “paddle” cutout. To correct you could file on the paddle and clearance it, which I don’t like, or you could put it in the mill and machine it out but personally I find it easier and faster to just use a 1/8″ carbide burr in my Foredom tool (or Dremel) and remove it. Choose which ever method you feel most comfortable with. Make sure to clean out the slide.
Correcting issues with fitting check #3- This particular issue can create a dilemma for some. Usually because the original sear lever was protruding well above the center rail and everything was working fine, so what’s the concern. And with that thought will skip past this part. If this was a normal out of the box pistol with an 8 pound trigger pull I might agree up to a point. But you now have a pistol with an Improved Sear Lever and at a minimum probably have a spring kit installed or actually have also done a trigger job.
In certain pistols that have had a trigger job performed if the sear lever protrudes above the center rail excessively it can cause the hammer to follow to half-cock with the trigger pulled when the slide is cycled. So I consider it one of those “best practices” to ensure the sear lever is fitted properly in this area.
The Improved Sear Levers are hardened so they will be tough to file but reduce it to where it is close to flush with the center rail. Be careful not to thin the nose too much. Sometimes worse case the lever has to be bent and reshaped. Note- factory sear levers will typically require different corrective action to eliminate protrusion above the center rail.
Finishing Up
Now that you have everything corrected you can reassemble the slide with extractor and firing pin assembly. Install the Improved Sear Lever with it’s spring. I use my slave pin to help align the sear lever hole with the pivot pin hole when driving the pivot pin in.
Again we want to check to make sure the Improved Sear Lever has free movement. Now completely reassemble the pistol. If you haven’t taken the magazine disconnect out you will need to insert an EMPTY magazine to perform the following checks.
The first thing we want to check is the overtravel. This is normally not an issue but we still need to check it. Normally there will be some reduction in the overtravel with the Improved Sear Lever. With the hammer cocked, use a thumb to keep the hammer from falling and pull the trigger. Looking into the back of the pistol you should see the sear lift out of engagement with the hammer full cock notch. Now ease the hammer forward. The half cock notch should clear the sear with out bumping and have a little clearance, I like at least .003″-.005″.
If you don’t have enough overtravel then you will need to find out where the problem lies. It could be the trigger nose (it limits the overtravel), it could be the trigger bar (it’s possibly too short), or it could be the sear lever bottoming in the slide cut and limiting its movement due to a dimension problem.
Now we need to check the trigger reconnect. Again, normally not an issue but we need to check it. With the trigger pulled cycle the slide. Release the trigger and then pull it, the hammer should fall. You can do this several times to confirm that there are no issues. If the trigger fails to reconnect most likely it is in either the trigger return itself or the trigger bar.
Last thing we are going to check for is hammer follow with the trigger pulled. Lock the slide back, pull the trigger and hold it, now drop the slide. The hammer should stay cocked. Again repeat several times. If the hammer follows with the trigger pulled, which is rare, then usually the trigger bar is the issue. Other culprits are not having the sear lever spring installed or the sear lever spring has been cut. Also a bad trigger job or a sear spring without enough tension on the sear can be at fault.
Test Fire
Now you are ready to test for function. Remember to use the “Safe” Test Fire Function Check. This is another one of those “best practices” that you should get in the habit of doing whenever you do any action work on a semi-auto pistol. All shooting should be with two hands for ultimate control as you go through the test fire process.
So what is the “Safe” Test Fire Function Check?
You start by loading only two rounds in the magazine. Shoot. If everything works okay load two more rounds and shoot again. No problems, load five rounds and shoot, still no problems repeat with another five rounds. If at any time you experience any Hammer Follow, Hammer Follow to half cock, failure in trigger return or anything that doesn’t feel right, STOP! and evaluate, don’t keep shooting. Once everything checks out fill the magazine and shoot away.
All the above does is insure that if you would have a problem in the beginning that you don’t end up with a full-auto surprise.