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External adjustability for the Benji trigger: Quick, simple, and zero cost.

December 12 2015 at 7:56 PM

Steve in NC  (Login pneuguy)
AR&P

Here's a quick and dirty mod' that implements an external adjustment for Benji trigger sears that, in all humility, I really don't think could be much simpler, cheaper, or easier.

photo BenTrigA1_zpsenekxxaj.jpg

Just in case it's not obvious how it works, it's kind of a don't raise the bridge, lower the river thing.

The scrap of innertube pushes the trigger housing away from the bodytube (and therefore away from the hammer), taking the sear along with it. This increased spacing reduces engagement between hammer and sear, which is then partially adjusted back out with the housing screws (screws on both sides adjusted symmetrically to maintain balance) until trigger creep suits the tastes of the shooter.

It works with both the stock sear and SuperSear, but since the stock sear is not a true 2-stage design, it's impossible to adjust away all the 2-stage creep without compromising safety. With the Super, by contrast, since it is a true 2-stage, you can.

Although the housing screws typically end up slightly offset from their countersunk holes in the body tube, as shown in the photo this is really neither visible nor (IMHO) cosmetically objectionable.

photo BenTrigA2_zpsro42qwlm.gif

This may be of particular interest to users of my Benji' SuperSear, which is available both as part of the DIY ACP392 conversion kit (currently for sale in the Yellow Classifieds), and for sale as a separate part from a well known retailer.
Steve

 
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gubb33ps
(Login gubb33ps)
YF

Neat...will try it.

December 12 2015, 9:44 PM 

HAve an old Challenger 2000 co2 that uses the same trigger system...will give the idea a try.

 
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Steve in NC
(Login pneuguy)
AR&P

Cool and thanks! One caveat.

December 12 2015, 10:13 PM 

If you're using the stock sear with its only simulated "2-stage" trigger, you'll need a pretty thick spacer and, as mentioned in the OP and as I'm sure you already know, adjusting for zero creep means adjusting for zero engagement. Yikes!
Steve


    
This message has been edited by pneuguy on Dec 12, 2015 10:35 PM


 
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gubb33ps
(Login gubb33ps)
YF

Works

December 13 2015, 9:58 AM 

Works as advertised!

Test rifle:

photo 5470870c-d7f5-48cf-89df-c88b298c0bfe.jpg

Trigger unit: (that light striker, weak spring, and a tiny gas port on the valve is makes this one a 4.5-5 foot pound rifle, but with 80-90 shots per 12gr.)

cr trigger photo DSCF0006-1_zpsd91efc0f.jpg

Used harder plastic shims in various thicknesses (mostly from 12gr shells/ wads). Not really compressible, but I didn’t have anything “squishy” in the right thickness.

No real trigger gauge, so I “cheated”.

TRIGGER PULL GAUGE CHEAT:
With rifle captured loosely between thumb and fore finger, pointed down, on top of a digital kitchen scale, the weight of the rifle is 6 pounds 10 oz. CAREFULLY and SLOWLY pulling up on the trigger and watching the scale read out, can get the weight where the sear tripped. Difference between the two would be the trigger pull.

Had worked this trigger over for smoothless and a crisp pull, so it’s starting off way-better than a stock 387/392. Never did anything about the take-up as it never really bothered me; it’s not 1st stage as there is nearly no real weight to it, but what weight it adds to the trigger pull is minor (scale claimes it is something like 1 ½ to 2 oz).

As tuned: 1 pound 8oz.

.032” shim = 1 pound 2 oz.

.054” shim = 14oz. BUT, the trigger malfunctioned about 2 out of 5 tries.

Evidently the .054" shim as a little too much. If I used a compressible shim, could just change the shim thickness by how tight the unit was attached, but as I was using firm shims, decided to back track to the .032” shim and a 1 pound 2 oz. pull. Boucned the rifle around on its butt and it didn’t fire. Will see what it turns out to be in pull (and safety) once the sear has mated up to its new angle.

May go to a "split the difference" shim thickness later.

Thanks.


    
This message has been edited by gubb33ps on Dec 13, 2015 10:04 AM


 
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Steve in NC
(Login pneuguy)
AR&P

Glad you're enjoying this simple trick. Used with a SuperSear, it's really a delight...

December 13 2015, 11:31 AM 

...because it allows, not just reducing 2nd stage weight, but controllably dialing away absolutely all perceptible creep right to the razor's edge of no 2nd stage at all - all with complete safety.

Using a Super right out of the box with a raw unpolished hammer, 1st/2nd weights of ~8oz/1lb are available, conveniently adjusted for with the gun fully assembled since the screws sit naked out in the open. happy.gif
Steve


    
This message has been edited by pneuguy on Dec 13, 2015 11:33 AM


 
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db
(Login Diamondback)
YC

Cool. Perhaps layers of black tape would work as a spongy, readily available shim? nt

December 13 2015, 3:49 PM 

nt

 
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Steve in NC
(Login pneuguy)
AR&P

Considering how many different kinds of tape there are...

December 14 2015, 11:12 AM 

...I'm sure you could find something that would work.
Steve

 
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Old Carver
(Login NC_Carver)
YF12

Thanks Steve.. nt

December 14 2015, 2:49 PM 

Common courtesy isn't.

 
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gubb33ps
(Login gubb33ps)
YF

Hard headed

December 14 2015, 5:31 PM 

Went ahead and kept playing with firmer plastic shims, but shimmed both the front and rear of the trigger assembly...not that it's better, just more "level".

Stock parts (with a little fitting) won't pass the bump test at less than 1 pound (I likely bump pretty hard) but will stand 1 pound 2 ounces.


Something I've been wondering. If Crosman has any Challenger 2000 parts...and has that lighter weight striker...might be worth a try in an air concerving MSP.

 
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Steve in NC
(Login pneuguy)
AR&P

As I commented in the OP, since the stock trigger isn't a "real" 2-stage design...

December 14 2015, 6:06 PM 

...it's really not surprising that safety considerations limited how far you could take things.

The same limitation doesn't apply to the SuperSear for reasons already discussed.
Steve


    
This message has been edited by pneuguy on Dec 14, 2015 6:38 PM


 
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JC Richardson
(Login JCRichardson)
YF12

Amazingly simple

December 24 2015, 1:58 PM 

I just tried this on my 397 with stock sear (waiting to get a super sear when I have more airgun funds).

I just cut a piece off of a wide rubber band and used that as a test, and even though the difference was subtle, I could definitely tell it made a difference, and will try two layers of rubber band taped together, since I have a feeling it's just that the rubber bands are too compressible.

Wonder if the change could also be attributed to changing the angle ever so slightly of the sear/hammer engagement, since I'm only shimming the back and not the front as well?

JC

 
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Cal
(Login calinb)
YF12

Wow--or to put it as Steve Jobs once said, you

February 3 2016, 2:16 PM 

"Think Different," Steve_in_NC! happy.gif

I think I'll use innertube or other spacers to find the magic spacing. Then perhaps I'll use black Acryglas bedding epoxy on the housing to make the adjustment permanent and reproducible to ease assembly after rifle teardowns (but still removable, if ever necessary). If I endeavor to put the epoxy on just barely a little too thick, it should not take long to sand it down and re-achieve the optimum but permanent spacing again.


    
This message has been edited by calinb on Feb 3, 2016 2:17 PM


 
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