My Benjamin 392

[rsterne]

Eric, thanks for that, and the link to your 2-stage setup.... You are correct, I don't need to change the angle of the entire back edge of the sear, just enough for the sear engagement, which cannot be larger than the depth of the engagement ring on the hammer.... That will mean a LOT less of the sear needs to be removed, but I still think the best way to do it is to make a jig, and rotate the sear on it's pivot point, gradually moving it closer to a sanding disc.... That will guarantee the correct angle so that it won't push the hammer back against the hammer spring.... If I understand you correctly, clamping it to a framing square would also work, if you had the pivot hole bisected by the edge of the square, and the tip of the sear that you want to remove also at the edge of the square....

I like 2-stage triggers, but not having access to TIG welding, and not wishing to machine a whole new sear, I will probably just grind a groove in the top of the sear, leaving the tail end untouched.... I think your 1st stage travel is the "creep" that is complained about.... you are just making use of it with increased leverage, like the AoA super sear does.... except yours is adjustable.... 

Bob

[Blutroop]

Bob. I have access to a Tig welder. I can do aluminum, stainless and steel. If you can send a spare up to me and draw up what you need I can knock it out for ya.

[Hack21]

If I understand you correctly, clamping it to a framing square would also work, if you had the pivot hole bisected by the edge of the square, and the tip of the sear that you want to remove also at the edge of the square...

Bob, Your interpretation of my vague statement is correct. I clamped the sear so that the pivot hole for the sear and the corner that would last disengage from the hammer were on the same plane created by the short leg of the framing square. I finessed it a bit so that the angle ended up being closer to 5° from what was just described as I wanted to stay a bit conservative but much less than the 17° that I crudely measured the original angle to be.

The orientation of the sear to the square was such that the trigger engaging protrusion was away from the square so that it could hang off of the edge of my table saw top when I did the lapping. The sear surface had to protrude past the bottom surface of the square, so I shimmed the other end of the square between it and the table by roughly the same amount during lapping. I used a smaller square held 90° to the first square to avoid a rocking action as I did the lapping. I polished to a mirror finish after I was done.

If you grind an arc and then there is any wear that happens later the trigger might be a bit precarious. Tim's post specified that case hardening was required. I didn't do this and will inspect for wear and do so in the future if necessary. It seems to me that the perimeter of this ground area should still be hard assuming you haven't removed material from the top or sides as well. This is assuming the part was previously case hardened by Crosman. If the part was actually through hardened, then we are in even better shape.

With the sear angle change, I am cautious and recock the gun if I have placed my finger on the trigger and pulled through he first stage and then let off as sometimes happens in the field. I don't want to be walking around with the hammer hanging on by only the last 0.005" of engagement! With the factory angle, I have little doubt that the hammer spring wouldn't push the hammer back ahead and draw the sear back into full engagement. With the 5° angle, mirror polish, stoning on the hammer, and some lube it feels as though this is still happening (second trigger squeeze feels that same as the first), but I am careful none the less.

Thanks.

[rsterne]

Jeremy.... thanks for the offer, maybe on a later version I might decide to take advantage.... 

Thanks, Eric, I like your idea of leaving a slight angle instead of an arc, in case of future wear.... I will mimic your procedure when modifying my sear.... and of course polish and lube all surfaces.... Did you change the angle on the engagement ring on the hammer, just polish it, or both?....

I wouldn't be surprised if I end up making my own hammer anyways, depending on the requirements of retaining air....  …. As I understand it, the forward band on the hammer is only for the cocking pin to draw it back, isn't it?.... The "1/2 cock" (click) you get when first drawing the hammer back is the rear band catching on the front sear, I believe....

Bob

[Hack21]

Bob,

I simply stoned the edge of the hammer to have a very small radius and to remove any burs or dings. This was recommended by Tim in one of his posts and makes sense since it is that edge that actually engages the sear surface. I polished this edge as well.

I am not totally certain on the design intent for the other hammer engaging feature on the sear.  I would imagine that it might catch the hammer if the bolt slipped from someone's grasp while cocking the gun. If you decocked the rifle (which you now can), it would keep the hammer away from the valve in the event of a hard drop or bump. I didn't do anything with this feature other than to ease the hard edge that was left from stamping operation.

I believe you are correct about the front band of the hammer acting as a bearing surface but not engaging with the sear. From studying your other work, I suspect you will end up with a lightened or lighter replacement hammer as the lift will probably be very low otherwise to achieve your object.

Thanks for bringing us along on this project. I am excited to see what you are able to do with it!

[Psipumper]

You should make a hammer or two.

[Hoosier Daddy]

Assuming you have seen the "super Seer" Bob...

[Hack21]

Assuming you have seen the "super Seer" Bob...

All,

The super sear that AOA sells is not the version pictured any longer.  It is an aluminum part with a roll pin insert to act as the hard surface for hammer engagement.  There aren't any inserts for the portions that are touched by the trigger.  I was a bit turned off by this, but it may infact work great?

Thanks.

[Hoosier Daddy]

Interesting, this is what I was referring to.
https://www.airgunsofarizona.com/blog/2009/03/installing-benjamin-supersear.html

[Hack21]

Scott, Here is a GTA thread on the subject...

https://www.gatewaytoairguns.org/GTA/index.php?topic=55104.0

[rsterne]

Nice selection of hammers, Charles.... is the heaviest one Tungsten?.... I will be going lighter, if anything, not heavier....

Scott, I like the concept of the Super Sear, the company who makes them, and whoever cheapened the design not so much.... I'll stick to doing my own mods....

Bob

[DanD]

...
The super sear that AOA sells is not the version pictured any longer.  It is an aluminum part with a roll pin insert to act as the hard surface for hammer engagement.  There aren't any inserts for the portions that are touched by the trigger.  I was a bit turned off by this, but it may infact work great?
...

I have the new version, and it does work great. I haven't been running it long enough to know about long term durability, though.

[Hoosier Daddy]

Bob, I was just pointing that out for reference... figured you would machine your own.
 But there is nothing like reverse engineering ones baseline to improve upon.

[Psipumper]

Nice selection of hammers, Charles.... is the heaviest one Tungsten?.... I will be going lighter, if anything, not

Bob

The heavy one is tungsten. Only good for paperweight , verified. I will say it gave the gun that springer feel.
The two lightest hammers (25 and 35) are for balanced valve. The 59 gram is  the one I use in each of my guns.
I mentioned a “ new improved hammer “ in one of my earlier threads. I didn’t elaborate on what the improvement was.
The steps are spaced differently than the original hammer. This spacing increases the hammer stroke from .781 to 1.00 inch.
A added benefit of this increase is the probe is further back making pellet loading a lot easier. The countour shape of the new improved hammer slides much easier over the sear. Feels smooth and expensive pulling bolt back.
The spring pocket is much deeper allowing spring selection.
I think that covers it. Well maybe the 10 degree angle on the sear engagement step.
I should give it a name other than secret new improved hammer.

Charles

[rsterne]

Today was trigger day.... I have been reading about tuning the 392 trigger group, some of the best info was from Timmy@Mac1, who makes the Steroids, of course.... I also read up on the AoA "Super Sear", which has undergone a downgrade, and asked some questions of others who have tuned their own 39X triggers.... I decided to do my own tune, with a bit different "flavour".... Let me make a warning right now about trigger safety.... Many attempts trying to make a conventional trigger into a 2-stage can leave you with an unsafe trigger.... If you don't understand what a "balk fire" is, then you need to read up on it, because it is VERY dangerous.... The short summary is that if you modify a trigger incorrectly, you may create a situation where pulling the trigger through part way (eg. to the beginning of the 2nd stage) can leave a trigger hanging because it doesn't return to full sear engagement.... Imagine a situation where a trigger normally has 1/16" of sear engagement, and without you realizing it, an aborted shot leaves you with the sear engagement only 0.005".... The gun could fire by bumping it.... It you don't know what you are doing, leave your trigger alone.... That means DO NOT copy what I did, because get it just slightly wrong, and your gun may be an accident waiting to happen.... This is a report on what I did, not a recommendation that you follow suit....

The stock 392 trigger is extremely safe, but a very heavy pull weight.... Most of this is because of the geometry of the sear.... When you slowly squeeze the trigger, you are actually moving the hammer back slightly against the hammer spring.... This is most of the reason for the heavy pull weight, but it also guarantees that the trigger will reset and not leave you hanging.... To get around this, I followed the lead of Tim's steroids, and reshaped the sear so that when it is pulled down, it does not move the hammer back.... This makes it much easier to pull, but it won't return if you don't fire the gun and release it.... Tim also grinds the engagement ring on the hammer to match the sear angle, and then rehardens both components for longevity.... I did neither, I'm willing to see how long it lasts, and repair it if it doesn't....

The sear only engages the hammer by the depth of the rear ring on the hammer.... The front ring has nothing to do with the trigger, it is there so that the SHCS on the bottom of the bolt can cock the gun.... There is a second bump on the sear that gives you a "1/2 cock" position if you pull the bolt back a short distance, which causes an audible "click" and leaves the hammer not touching the valve stem.... The angle on the rear sear is the one I worked on.... I changed it from about 17 deg. to about 5 deg.... Basically I made it almost part of an arc of a circle centered on the sear pivot pin.... I was going to make a fancy jig, but got lazy and just did it by hand with a diamond file, checking the angle until I was happy with it, and it didn't move the hammer back when I squeezed the trigger.... I then polished it, and I also polished the top of the tang that the trigger rubs on, and the bottom of the radius on the front part of the trigger that pushes down on the sear tang.... Here is a photo of the sear after I changed the angle and polished it....



You can clearly see how much I changed the angle.... Now WHAT you are asking yourself is that SHCS doing there?.... 

After getting the trigger working the way I wanted, including installing a MUCH lighter coil spring behind the trigger, I found out just how bad the "creep" in the trigger really is.... Since the sear is engaged well over 1/16", the trigger moves back a long ways during the period that sear is moving down on the hammer engagement ring.... I wanted to shorten the engagement, and since the lighter spring behind the hammer provides a "fake" second stage that was very short, I thought long and hard about how to make it "ACT" like a 2-stage by shortening the sear engagement.... The result is much like a worked over QB trigger, which can be quite nice.... It has a "fake" first stage where all that is happening is the trigger is moving against a light spring, and the sear adjustment allows you to set how far the sear moves once the trigger starts to move it.... The problem was, there was nowhere easy to put an adjusting screw in the housing, because it had nothing on the sear to push against to set the sear engagement.... So, I added that screw in the spring hole, and added a 1/8" long #6-32 setscrew in the top of the trigger housing to push against it.... Bingo, I had an adjustable sear engagement, that looks like this (sear shown upside down)....



The setscrew "A" pushes against the head of the SHCS "B", and the further you screw it in, the less the sear engagement is.... Now HOW did I get that 6-32 SHCS into the spring hole in the sear?.... With great difficulty and a little luck....  …. If the sear was not hardened, I could have just tapped the hole, but an HSS tap wouldn't do more than scratch it.... The hole is 0.125", and a #6 screw is only 0.135", so I drilled a 1/16" hole through the screw for the tang on the spring, shortened the screw to a few thou more than the thickness of the sear, put some Loctite 638 on it, and using brute force, wound it into the hole in the sear from the left (under) side, opposite where the hairpin spring is.... I then peened over the end of the screw, and figure it won't come out.... That gave me a "bump" on the underside of the sear for the adjusting screw to push against, so all I had to do was mark where it needed to go, and drill and tap the housing (very close to the edge) for the adjusting screw.... I screwed the adjuster in flush with the top of the trigger group and assembled it for initial testing.... This gives me the minimum sear engagement, and at that adjustment, the assembled trigger looks like this....



I didn't even know if the sear would catch the hammer, but to my surprise it did.... and the trigger felt GREAT !!! ….  …. The first "stage" was much longer and very light (because of the light trigger spring), and the force increases significantly when the trigger touches the tang on the sear, because of the fairly heavy (and stock) hairpin sear spring.... I didn't know how much engagement the sear had, and the answer was "not much", as virtually any movement of the second (actual) stage fired the gun.... I tried it several times, and it felt reliable, and I also cocked the gun and banged it around in every direction, thumping it against my workbench and with my fist, and it never fired once.... My conclusion was that the sear, with the adjustment screw flush with the top of the trigger housing was "safe", but with VERY little engagement.... I disassembled the trigger once more, lubed all the contact points with moly paste, and put a drop of blue Loctite on the sear adjusting screw and set it 1/2 turn above flush.... In this position it still misses the bottom of the main tube, and I love the way it feels.... It is nice and crisp, and you can move it a whisker on the 2nd stage pull, but for all intents and purposes it breaks cleanly, with no noticeable creep.... a great hunting trigger, IMO.... Incidently, set this way the "half-cock" does not work.... You can hear it click over the front sear, but with the sear in this position, it won't catch the hammer.... If you back the adjusting screw out all the way, it hits the main tube, but the sear would be fully engaged, just like a stock gun.... It looks like this backed out all the way, so that the head of the SHCS is touching the inside of the trigger housing....



If you wanted to have the full sear engagement, you could just remove the adjusting screw so it wouldn't hit the tube.... I didn't see how far out I could screw it and still miss the main tube, but maybe 1 turn above flush?.... The point is, I can get a safe sear engagement and still have a nice trigger, so I'm a happy camper.... Remember, do NOT attempt this unless you know what you are doing.... YOU are responsible for your safety and that of others, don't blame me if you have a problem.... YOU HAVE BEEN WARNED !!!!

Bob

[Techie]

Wow, must have been interesting drilling that 1/16" hole through that socket head cap screw. I guess the indented head made it self-centering.

[Psipumper]

Bob, I like the term “ fake first stage” to describe that movement.
I like it without that but some may not.
Trigger feel is a a deep subject.

The safety does not block the sear when on, if it did you could not cock the gun when the safety was engaged.
Full sear engagement is needed for sure.

Glad you got it done.

I have 2 mm trigger travel at two pounds pull. The sear is fully engaged with no fake first stage.

[rsterne]

I just used a small center drill to get it started.... Actually high-tensile SHCSs are "tough" but not hard.... a good HSS bit works fine.... If I had it to do over again, I would leave the screw about 1/32" longer than the thickness of the sear, and after installing it I would use a centerpunch in the drilled hole, with the head of the screw on an anvil, and spread out the end of the screw to prevent it ever coming loose.... Oh, I forgot one small thing.... The SHCS had a very slight "shoulder" (actually, just unthreaded for the last 1/32" under the head)…. That is why you normally have to counterbore a hole for them about 1/32" with a clearance drill.... Since I could not drill the hardened sear, I machined that last 1/32" under the head to the depth of the threads, so the screw could "tighten" up right against the sear....

Charles, I assure you that the safety still works perfectly.... It does not block the sear, but the tang on the front of the trigger.... As long as the trigger blade does not move forward further than intended, which is set by where the front of the blade contacts the front of the slot in the trigger housing, you have not changed how the safety functions.... My trigger has to be pulled a long ways past the safety interlock before it even touches the sear.... I have had a lot of QB triggers, and I always set them up the same way.... as a "fake" 2-stage.... The sear engagement is adjustable on the QB (stock), and I set it for about 1/32" of sear engagement, which is enough you can drop the gun or bang it around without it firing.... I prefer having a lighter 1st stage, as it helps me feel the trigger when my hands are cold, like they are in Grouse season.... As you said, trigger preferences are a very personal thing.... For hunting, I like a trigger in the 2 lb. range.... I just measured this one, and at 2.25 lb. on my simple fish scale (that I always use) it fits the bill perfectly....

Bob

[rsterne]

I decided today to make my velocity adjuster, which may become an SSG.... Here is a photo of the assembled parts....



The body is a piece of 3/4" diameter 6061-T6 aluminum 1.15" long (sized to fit the cavity in the trigger group)…. It is drilled and tapped 3/8"-24 NF for the front 3/4", and the back is drilled out with a Size "W" letter drill, which is 0.386".... That gives clearance for the shank of the adjuster, which is a 1.5" long bolt that has 1" of threads.... I drilled the bolt through with a #11 drill, which is 0.191" to provide a nice sliding fit on a piece of 3/16" drill rod.... There is a piece of it slid through the hole in the bolt in the photos.... If I decide to make an SSG, a longer piece of that drill rod will be the spring guide I will use.... The nice thing about using 3/16" rod is that I can thread it 10-32 on the ends for the front spring seat and adjusting nuts....

You can see a setscrew protruding from the top of the aluminum housing.... It is a #4-40, installed in a tapped hole with Loctite.... The purpose of it is to prevent the round bar from rotating in the trigger housing.... It fits into the slot in the top of the housing.... The next photo shows the adjuster sitting in place in the trigger group....



I drilled the front of the housing out with the Size W drill, drilling through the original spring seat.... The back of the housing is drilled a bit larger, with a 7/16" drill, as it just needs to provide lots of clearance for the 3/8" adjuster bolt.... You can see another setscrew (a #8-32 that is 1/8" long) in the bottom of the adjuster housing.... It has a short piece of 1/8" plastic rod under it, pressed against the side of the 3/8" adjuster threads to act as a brake.... This allows me to change the position of the adjusting bolt, but prevents it from adjusting itself.... I do most of my adjusters that way....

The way the adjuster is currently set has the front of the adjuster bolt in the same location as the original spring seat.... so the gun will behave as if the adjuster wasn't there.... The 1.5" long bolt can move forward about another 1/16" to increase the hammer spring tension, and has more than 1/2" of adjustment to the rear, for a total of about 5/8".... If I need a more forward position for the spring seat, I can add a spacer/spring guide to provide that.... but in reality I will probably need to move the adjuster back, to allow for the installation of an SSG at a later date.... The ability to adjust the hammer strike will greatly enhance the ability to tune the gun as a retained air pumper (RAP, aka ACP - air conserving pumper)….

I assume that existing ACPs, such as that sold by AoA, must have some way of tuning the hammer strike.... but if so, I don't know what they use.... I think that this version will work great....

Bob

[Psipumper]

Wow. That is some fine work.
A hydroformed air tank in the place of the pump handle it could be an instant PCP.
Very nice.