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PostPosted: Wed Jul 02, 2014 11:58 pm 
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One of our stickies here is a method for refining the OEM trigger in a Vepr. The principles can apply to other trigger groups.

However, many AK pattern weapons do not have as good a starting point. Also the Vepr trigger may need to be replaced for 922(r) reasons, or you may simply prefer other trigger characteristics. Another excellent option is the RSA (Red Star Arms/ Power Customs) AK trigger. (IMO the best available for the AK). The Jard trigger is more expensive and has a track record of breaking. Arsenal is more like a US clone of a surplus comblock trigger.

If you want an excellent trigger with minimal travel and a 2-5 lb pull for ~$23 and an hour of work, read on. Do NOT ATTEMPT TRIGGER MODIFICATIONS UNLESS YOU COMPLETELY UNDERSTAND THE WORKINGS AND ASSUME ALL THE RISK. BE SURE TO THOROUGLY TEST ANY ALTERATIONS IN A VERY CONTROLLED SETTING.

This is a method for using a G2 Double Hook trigger, plus a spacer, in almost any kalasnikov designed to use a Single Hook trigger. The principles here will apply to a single hook trigger as well to make the pull lighter and smoother, but you need the double hook to have the short throw. The over travel stop method discussed below will not work in a gun that has two slots to allow for a double hook.

Image
The first step is to use a diamond file or ceramic knife sharpener or gunsmithing stone to polish and square up each of the engagement surfaces. If you don't have those tools, you can get a multipack of automotive sand paper from 200 grit through 600 for about $3. back that with a credit card or a file and you are in business. We are absolutely not changing any angles even a little or rounding corners. Nor are we shortening engagement surfaces! Shortening the hook(s), disconnector, or hammer wing surfaces on a G2 can result in a condition which allows the hammer to slip between the disconnector and the hooks thus either firing unintentionally or following the carrier home. Bad news. Don't do that. There is a better way. The G2 has casting mold lines at each of the points that needs to be perfect. This results in a rough pull, and sometimes a sticky trigger that will not reset. First, we need to place a flat stone flush with the surface of the underside of the hooks and work it back and forth until the finish is gone and they are exactly in one plane. You can use a permanent marker as machinist's dye to see where irregularities are. Next do the same to the underside of the disconnector. If this leaves a sharp corner, very slightly break the sharp edge with about 4 passes of sand paper or a sharpening stone. Now the same for the sides and back of the hammer wing. When you are done you should be able to install the trigger group and see a huge improvement in feel. Coat all the engagement surfaces in marker and cycle the trigger group repeatedly. When the marker rubs off, it should be even, not shiny in little streaks. This will prove you have trued up the surfaces to eachother. Bright spots are high and need a little more action. Work your way up to about 600 grit, but if you want, you may go as fine as 2000.

Now for the cool part:

The basic principle is based off of the fact that a double hook trigger will not work in a single hook gun. This is because the floor of the receiver lacks a slot for the right hook to pass through. This means the trigger cannot pivot enough to release the sear from the hook. We will turn this problem into a benefit by cutting a step into the underside of the right hook that allows the trigger just enough to function. Then we will remove a tiny amount more material for reliability and for follow through. Thus you can have as little as 1/64" of overtravel in a reliable firearm. This part of the modification has no impact on reliability or safety. It just removes needless slop.

The next phase is to tune the pre-travel by putting a spacer under the back side of the trigger body. I like to use a rectangular piece of sheet metal about 1/16" thick, and secure it with the rivet or screw which holds the trigger guard. If this rivet is already set, you can use the pistol grip nut to hold it down. You can also simply get a fender washer of the right thickness with a 1" outer diameter. IMPORTANT. This spacer has the effect of partially pulling your trigger. It reduces the engagement of the hooks. Do not reduce the engagement between the hooks and the hammer wing below ~1mm. The actual amount your gun needs to be safe will need to be determined by you. You cannot have too much engagement, but too little is very dangerous. Make small changes and test. Do not treat the gun as safe or allow anyone else to use it until you have tried to create a bump fire by holding the gun loosely. The gun should not fire unless the gun is deliberately fired.

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PostPosted: Thu Jul 03, 2014 12:17 am 
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Joined: Fri Sep 28, 2012 10:38 pm
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Location: Arkansas, USA (NWA)
Beautifully done, sir!  Thanks. 

You did a great job of putting these things in simple terms and clearly explained what each thing does. 

Not sure if you want to add the modification of the hammer's striking face.  I forget. Does the Hammer axis need to be ground for the BHO or is that just the S12?

Great pictures too!  That tip about the marker as machinist's dye is very useful. Keep up the excellent work!

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PostPosted: Thu Jul 03, 2014 12:30 am 
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Video guide is here: https://www.youtube.com/watch?v=H5GmniFShgA

A quick show and tell for tools. https://www.youtube.com/watch?v=oo_8RxO-78A&edit=vd

More to come:

Hammer refinement. This will show drag, clearance and strike angle correction. I believe V12s need the clearances too, but it has been a while since I looked in one.

Friction reduction.

Reliability diagnostics.

And if I can ever convince a friend to let me manhandle his gun, port work. - It's tough to show that when your guns already run flawlessly.

_________________
P.M. me if you want help:
modify or fix your gun

shotguns, some gunsmithing, reloading, fabrication, knife making, etc.

I'm a firearms/NFA attorney in Wa. Let's combine business, pleasure, and stamps.

http://www.youtube.com/user/armaggedonite


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PostPosted: Thu Jul 03, 2014 2:37 am 
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Nice graffic!

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PostPosted: Thu Jul 03, 2014 2:52 am 
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I can't claim the original. I just altered an old one.

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P.M. me if you want help:
modify or fix your gun

shotguns, some gunsmithing, reloading, fabrication, knife making, etc.

I'm a firearms/NFA attorney in Wa. Let's combine business, pleasure, and stamps.

http://www.youtube.com/user/armaggedonite


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PostPosted: Sun Jul 27, 2014 3:26 pm 
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Location: S.FLA.
GunFun wrote:
Video guide is here: https://www.youtube.com/watch?v=H5GmniFShgA

A quick show and tell for tools. https://www.youtube.com/watch?v=oo_8RxO-78A&edit=vd

More to come:

Hammer refinement. This will show drag, clearance and strike angle correction. I believe V12s need the clearances too, but it has been a while since I looked in one.

Friction reduction.

Reliability diagnostics.

And if I can ever convince a friend to let me manhandle his gun, port work. - It's tough to show that when your guns already run flawlessly.

Gunfun...
Excellent video.. Definitely my next mod.

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PostPosted: Sun Jul 27, 2014 3:41 pm 
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Thanks. It came in longer than I was trying for, but I wanted to err on the side of people thoroughly understanding what they are doing before starting.

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P.M. me if you want help:
modify or fix your gun

shotguns, some gunsmithing, reloading, fabrication, knife making, etc.

I'm a firearms/NFA attorney in Wa. Let's combine business, pleasure, and stamps.

http://www.youtube.com/user/armaggedonite


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PostPosted: Wed Aug 06, 2014 9:46 pm 
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Joined: Sat Nov 17, 2012 2:37 pm
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Location: Oklahoma
Got my Tapco G2 Double hook in today, and just finished getting it installed in my 54R. I had already worked over my stock trigger, and thought it was pretty good, but this is far and away a better trigger.

Outside of relieving the necessary spots noted by GunFun, all I did was polish all of the contact points with wet/dry sandpaper, starting with 400 and working down to 800 grit. My Vepr is a slant back, so the stock adapter made it more difficult to insert a shim for pre-travel, but after messing with it for a while I've decided that I like having some take-up with this trigger. It breaks at 3# or just under, and although kind of long it's butter smooth. I feel more comfortable knowing that I have plenty of engagement between the hooks and the hammer, and it's very predictable and "stage-able".

My only concern is the slightly downward angle at which the hammer strikes the firing pin. It's the one thing I didn't check before removing and disassembling the stock trigger, which was necessary in order to remove the disconnector spring for the Tapco trigger. For those of you with 54R's, does your hammer do the same thing? I'm just concerned about possibly damaging the firing pin.

Thanks to GunFun for the instructions and video. It's really appreciated.


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PostPosted: Wed Aug 06, 2014 10:02 pm 
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Thanks for the gratitude.

I tried to address the hammer face angle in the video. Many people leave this without problems, but I always take the minute or two to correct the angle. You should not remove much metal. I chuck the hammer into a vice and mark the area which strikes the firing pin. you will find this to be about .25"x.25" I black it up with a marker, so I can see where metal is coming from. Then I place the file flat on this surface and move it about 3/4" of a degree. Then a few smooth strokes. until my little black square of marker becomes just a line at the bottom edge and it is done. I must stress that very little metal has to come off to fix this for a square strike.

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P.M. me if you want help:
modify or fix your gun

shotguns, some gunsmithing, reloading, fabrication, knife making, etc.

I'm a firearms/NFA attorney in Wa. Let's combine business, pleasure, and stamps.

http://www.youtube.com/user/armaggedonite


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PostPosted: Wed Aug 06, 2014 10:29 pm 
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Oops. It seems I uploaded the video, but it is on the digital cutting room floor. The original vid was getting way too long for most people's attention span. Anyway, this vid got "cut." It shows some of the thinking but doesn't squarely address the strike face.

I have a few static pictures that I took to make a seperate video which I never got round to. I would like to re shoot this clip with an unmodified tapco G2 hammer, but here I am using the russian take off out of an S12. It is already smoother than Tapco's trapezoidal shape.
https://www.youtube.com/watch?v=cD48ncWTGyo

Here is the least blurry picture I managed of an unmodified G2 hammer installed. Note the strike angle is not square, and the pronounced trapezoidal corners on the face.
Attachment:
Hammer G2 Unmodified.JPG


Now here the hammer is shown with just the strike angle corrected:

Image

Another shot for good measure:

Attachment:
Hammer Face Corrected.JPG


Finally, a fully contoured hammer: [Note that the smoothing of corners does not change the angle of the strike face portion, just the area above it for a smooth transition. It is important that the carrier fully push the hammer below the disconnector, with a bit extra.]

Image

Now as it would be when firing:

Attachment:
Hammer Face Fully Contoured 2.JPG

_________________
P.M. me if you want help:
modify or fix your gun

shotguns, some gunsmithing, reloading, fabrication, knife making, etc.

I'm a firearms/NFA attorney in Wa. Let's combine business, pleasure, and stamps.

http://www.youtube.com/user/armaggedonite


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