M*CARBO Brotherhood

Polishing Trigger Parts (Hammer, Sear, Trigger Bar)

This was my first attempt at this sort of thing but having a lot of experience at tuning downhill skis and sharpening tools I have been considering doing this for a while after watching some vids etc. (I am not a trained gunsmith and this is just my personal experience, I do this kind of work on my own guns only and assume any and all risks) After my 3rd. disassembly of the S2K internals to install spring kit, trigger bar, and then the other upgrades I was getting pretty familiar with the function of the various parts. I went about this very conservatively being aware of the possibility of altering the function and safety of the firearm and in anticipation of this I ordered an extra hammer and sear to experiment with (very cheap) and to preserve the original parts just in case. Any and all criticism/critique welcome as to make this a learning experience for anybody interested.

I broke out some of my best ski tuning stones but didn’t use the diamond grit/plastic files in the pic…


The original hammer on the left - note the slight difference

This is the orientation of the hammer and sear in the cocked position


These are the engagement surfaces


These are the surfaces before I started


I used some masking tape to protect the adjacent surface and worked the part on the stone, not the stone on the part

This is after just a FEW licks with the 250 grit stone being extremely careful to be as flat as possible on the stone, mainly just pulling towards me, not back and forth strokes. I used watery dish soap as lube and I didn’t make it totally flat at first, I worked my way through the finer grits so I ended up finally getting it flat with the 1000 stone. I think 400 grit would actually be coarse enough to start with less chance of over doing it.


Old sharpening trick to guide your progression - paint it with a sharpee and you can accurately see where you are cutting. Take just enough to remove the color

Once you get it flat hit it with some Flitz on a felt Dremel bit and BLING!


Next I did the trigger bar but just what I determined to be the engagement surfaces, I suppose you could just polish the whole thing. I initially took a 400 grit stone and flattened the face of the TB that rides on the sear. Here you can see the wear pattern on this surface after my initial testing of a few hundred rounds


For this I worked the stone on the part in a circular motion

I just worked this a little bit with the 400 stone, it flattened out really quick

A little Dremel work

I also touched these two edges with the Dremel only - they were showing some signs of engagement

I would say this definitely slicked things up and lightened the trigger pull just a touch, I’m getting mid to upper 4lb. range. I was getting low to mid 5lbs. before adding trigger bar and polish.

I cocked it (unloaded!) and I hit, bumped, smacked, and even dropped it on a carpeted floor pretty aggressively and it stayed cocked. This is kind of a drawn out report but it really wasn’t a whole lot of work once I got going. I have put about 150 rounds through it now and I’m TriggerHappy with the results :grinning: :+1:


@TriggerHappy That’s a fine presentation on how to polish these parts. Trigger pull weight?


Thanks Don, I meant to include that - just added a pic. :+1:


@TriggerHappy nice write up bud :+1:t2:


So long as geometry isn’t compromised, I like to polish/touch contact surfaces as well – yes sharpies are our friend for determining contact irregularities. I’d touched up my ejector and upper feed ramp too. Many thanks for the documented experience.


Yes , I think that really is the key. I feel pretty comfortable with what I did.


Very Nice Post ! A top view of the hammer surface to see end results of your fine Polishing job. If I may offer a suggestion to try, I use fine valve lapping compound and a drop or two of Oil does a nice job Also to see the progress on the contact surfaces while doing the work.


So now that it’s back together and a few rounds through it do you think you polished enough or you there’s room for improvements or is there something else you like to polish too

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Hey - thanks! Valve lapping compound is a great idea - I haven’t had anything to do with that since high school shop class lol I think I will pick some up…


Good question - I guess “room for improvements” is subjective… I don’t think the trigger needs to be any lighter for it’s purposes. I’m not a big fan of super light triggers except for bench rest target rifles. To me it feels smooth, clean and most of all precise just the way it is, most of the improvement due to the new trigger bar design I would say. Going forward I am focusing on getting the front sight and MB positioned and locked down (STILL waiting for shims) and then getting the sights and new optic dialed in. :+1:


Great write up…


Was just wondering more polishing would make for a smoother action

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That was well written even for someone like me. I dont have the skillset you seem to have but I think i can follow you directions.


I polished the SS feed ramp then filed the sear and hammer faces where they contact each other then polished them then buffed and polished the new trigger bar didn’t have any function issues I silicone any contact point I seen


@Jefft1967 Right on! I think you’ll be “triggerhappy” with the results - I know I am :grin: :+1:


You can put the final polished finish on it with mother’s aluminum wheels polish and a dremal polishing wheel. Will be slik as silk.

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TRIGGER HAPPY thanks for the great presentation and kicking me in the butt to help go forward with a story about installing the new trigger bar, which gives a significant reduction of take up travel of the trigger.

There are many disclaimers I want to put out there before I get started.

This is what I did to MY gun. The following is meant as informational and not given as advice. How i found out how this gun functioned is after replacing the trigger bar I still felt a “glich” in the trigger pull. I pulled my hair out at first. Then came back to MCARBO FORUM and saw a new thread by triggerhappy and started to think.
i saw triggerhappy’s diagrams and the light came ON. I started to look at partially assembled receiver and pulled he trigger with no safety in the gun(I KNEW THE GUN WAS SAFE BECAUSE WAS NO BOLT IN THE GUN) but that was a mistake because the hammer is now inside the grip !!! so I had to disassemble the grip again. this was good because now when i reassemble I will place bolt in before testing anything EVER AGAIN !!
So the gun is cock and bolt in place, I pull the trigger and then hammer drops and then I pull back and re-cock the hammer and let the bolt close on the barrel. Now I wanted to know "how does the safety work. I placed the safety pin in place with one e-ring and no detent ball but the safety still moves back and forth and can be placed in any position between safe and fire. At that point in time I realized that the bar moves up or down because of pressure against the surfaces of the pin and if i just lightly pulled on the trigger and move the safety pin back and forth I could “FEEL” all the rough places on the matting surfaces.
When the bar would engage the sear and also watch how the bar would push back and forth on the safety pin. I started to think when does happen I thought back to triggerhappy;s diagram and figured there is ANOTHER surface involved. Surface A (in the picture below) that contacts the safety pin that moves the TB up and down engaging the sear or clearing the sear.
if engaged with the sear, in fire position, then pulling the trigger makes the bar go forward pushing the sear forward off the bearing surface of the hammer. The smoother these surfaces are the easier it will be to make the sear go forward the smoother reducing the pressure it takes to move the sear.
I now have the surfaces so smooth I can stop the sear right before it passes from below the hammer and the hammer is released.Letting off of the trigger sets the sear in a “hair trigger condition”. At that point the ONLY the rear edge of the sear bearing surface is in contact with the hammer. making the very narrow piece of metal real smooth helps ALOT.!!!

Tools that i have to do the polishing described below. Not all sand paper is shown. depending on how much materal I want to remove I either start with flat/curved/round files or a grinding tip for interior surfaces or just course sand paper, then follow with 120/400/800/1000/1500/2000 grit paper( i wrap these different grits around a flat file to control removal of material) and always finish with Dremel and Flitz.
On large surface areas that carry high pressure loads (like the interface between the bolt and bolt tube, especially the front of tube right behind chamber) I like to use a good quality Molybdenum grease. I can also use this in PCP guns.
I use a 7x optic to check for progress go slow and adjust as required.

EXAMPLE of polishing
Notice the very small shiny surface at leading edge of bottom of bolt. I used a flat file to start radius. On some curved surfaces( like the curved surface on the rear of the bolt that starts the cocking of the hammer (after firing) I start with a light use of an appropriate grinding stone on a Dremel to create either radius or bevel to reduce impact vibration. Then went through sand paper wrapped around the flat file going from 120grit/400grit/800 grit/1000grit/1500grit finishing with 2000 grit then the Dremel tool and Flitz

Hammer bolt interface slightly radiused just enough to reduce drag (no dimensional change) just smoothed enough to reduce impact vibrations.

bottom of bolt where hammer rides when charging after firing. On the rear of the flat surface (inside of the curved face) I eased a slight radius where the bolt and hammer engage after firing to start cocking motion. I also put a slight radiuse on the appropriate face of the hammer. this all helps to reduce vibrations. It might even reduce time to cycle.

bolt hammer alignment in charging tube

I have cycled the gun and have noticed No change in function other than that of smoother action.

With all that in mind if someone does not know what they are doing and create any unsafe conditions while working on their on gun following the illustrations and concepts I am putting out here, accept no liability.

The pictures, for illustration purposes are here to show approximate orientation of working parts in different configuration at different times of operation.
cocked in safe mode

cocked in safe mode with trigger pulled
safety in fire mode gun ready to fire.

After gun fired

Trigger bar (with safety removed) with safety on. for illustration of movement of trigger bar not engaged with sear
Trigger bar (with safety removed) with safety in fire position (note the small gap below the trigger bar and safety pilot hole).

A side view of how parts stack when assembled (from rear)

Illustration of relationship between safety pin and trigger bar and hammer pin bushing in safe position pushing trigger bar down disengaging sear. The polished surface in these pictures does not show very well but all surfaces are mirror finished. there is a lot of pressure between the A surface of the trigger bar and the surfaces that rides on on the safety pin.

actual picture of above condition

position of trigger bar when in safe mode when trigger is pulled.

illustra!tion of relationship between safety pin and trigger bar and hammer pin bushing in fire position.

actual picture of safety in fire mode [Uploading: over view with safety in fire mode.

trigger bar position in fire mode when trigger is pulled

In all pictures above note the relative position of trigger bar and the hammer pin bushing. the trigger bar is puched against the hammer pin bushing when going into fire mode and when the trigger is pulled it drags over the bushing along surface B in the following diagram. Note the shiny edge of that surface i smoothed the square edge giving it a larger radius reducing drag.

I also cleaned up the edge of the hammer pin bushing reducing drag see illustrations above.

Safety pin polishing note, remove O-ring before polishing see illustrations above.
please see trigger bar illustration above for trigger bar/safety bearing surface A that is the surface that contacts the safety pin.
surface A polished with attention to edges.

A better picture showing polished safety pin surfaces. Look closely at step down surface on safety pin. that is me taking the picture. DO you think it is polished ?

Please see illustration above for trigger bar surface C. Consider all the edge surfaces of the trigger bar that are inside the notch as bearing surfaces.that is the contact area that engages the sear.
polish it and pay attention to making the outside radius of notch at C smooth !

Please see illustration above. The edge of surface B rides along the outer face of the hammer pin bushing and is pushed towards it as the safety pin moves from safe to fire. That caused the “glitch” i was feeling as i started to pull the trigger and again as I let off the trigger. I put a very narrow bevel on the bushing to make that transision seamless.

Below is picture of hammer profile note polished sides. Pay particular attention to hammer hook profile

Next 2 pictures are sear surfaces ,
Polish the sear trigger interface, if you look real close at the flat surface where bar rides against sear you can see the deeper mill marks that are still left on sear. just lapping the corner of sear where it rides up and away from the bar at firing makes that momentary contact effortless. Look at edge of hammer pin bushing, see bevel i created to smooth out the interface between it and trigger bar.

Sear hammer interface. Notice the very thin shiny edge of rear of sear hammer interface. Again, this is the last surface that touches the hammer hook while firing

Sear hammer interface

Edge of hammer bearing surface. Note the deeper mill marks are not the issue the higher surfaces are the issue. I drive this point home again…Again leaving the deeper mill marks there give an area where the lubrication (super lube w/ TPFE) has a chance to stay there and lubricate

Polished side of trigger bar. I put a very small bevel on the leading edge of side B (see illustration above) to ease the contact between trigger bar and hammer pin bushing

the end results trigger pull in safe mode SILKY SMOOTH

trigger pull when firing SILKY SMOOTH

All surfaces that were polished were soaked heavily cleaned with CLP,.let to soak for 5 miutes before whipping dry. All bearing surfaces, excluding Bolt and barrel hinge pin, were lubricated with SUPER LUBE before reassembly. Bolt and barrel hinge pin were treated with 60% high pressure, high heat, moly paste.

Sorry this got so drawn out but wanted to make sure it was explained.


Now I am going to post it then read it and edit. Please forgive my grammatical errors !!


@Turmeric Thanks for all the pictures, makes it easier to follow along.


Thanks to Triggerhappy. and I hope all that attempt to make their gun better can match or exceed my results.


Outstanding ! Thank you for A great Presentation ! and good pictures,:sunglasses: