Tuning Benji 392PA trigger

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Don.Chipmunk-slayer

Don.Chipmunk-slayer

Member
Aug 17, 2020
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Ohio, United States
I went ahead and bought the Baker Scope Mount, and I'm using a Discovery VT-Z 4-16X44 scope - a change from the Thompson/Center muzzle loader scope I was using. Following another person's suggestion, I sighted the rifle @ 10 yards with 5 pumps.

The rifle is now more accurate than I am, 3/8" groups are now the norm and I'm still getting full pass-throughs using .22 Gamo Redfire and Crow Magnum hollow points. I have yet to find a pellet this rifle does not like.

I think the biggest obstacle to accuracy is the trigger (at least in shooting groups, but I don't notice it when I'm actually pesting). The trigger pull has some weight to it, but that, I don't mind. The issue is that it's a LONG pull and I'm used to the two-stage trigger pull on my Glock 19 PB. That has less than 1/4" travel, a hard spot and then bang. The 392 just has a long pull with no indication when it's going to go off. But like I said, it's MUCH more noticeable when target shooting, not so much with chipmunks, but that's easily explained. The thrill of shooting vermin is much higher than punching paper, so I guess I just don't notice the pull.

I don't know if there is a "fix" for the trigger pull, but I do know that I DO NOT have the confidence in doing it myself.
 
The problem I had with mine was it was Gritty feeling. I took it apart and smooth out all the contact points and greased it. You can put a lighter spring in it too.They are very easy to work on. Once you take the barrel and action out, there is a little side plate that has little Allen screws in it. Just carefully remove the side Plate off Then it doesn’t hurt to take a picture of the trigger assembly while it’s together.But before you pull the parts out just noticed where the contact points are so you know exactly where to polish them.The parts are stamped steel and have a rough edge to them. I used a India stone and then some thousand grit sandpaper.There is even videos online how to do a trigger job on a Benji 392.
 
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Here's a photo of our 397PA trigger assembly.

I was just going to post a question about how to lighten our trigger when this came in...

I don't find ours to be long. I just find it to be hard. Heavy.

So along with this, does anyone know how to lighten the trigger of a Benjamin Sheridan 397PA or 392PA?

I've tried completely removing the trigger spring -- the coil spring behind the trigger. It's not really necessary, as the sear spring -- the torsion spring that raises the sear and works the safety -- does all the real work. I don't have a trigger scale, but difference was practically indistinguishable, except that sometimes I'd have to push the trigger back forward after firing it in order to cock it again.

I've had the thought that the best approach to try next might be to try to locate springs to replace both the trigger and sear springs that are about half the strength of these factory springs. But I'm not sure those springs are really the main problem.

I've polished the action a bit so everything is nice and smooth. When the trigger assembly is out of the gun, it is reasonably smooth and not unreasonably heavy.

I suspect that the striker spring putting all its force onto the striker and against the sear is what is really making this trigger so hard.

I'm a little leery of getting a lighter striker spring or of cutting off a few coils from our factory spring, lest I end up with a situation where the striker does not depress the valve plunger enough to completely evacuate the valve assembly's compression chamber of the compressed air. That could cause other unwanted problems.

I have a few ideas of other things to try, but I thought it might be better if I just ask here first if anyone has successfully managed to lighten the trigger of one of these things. They've been around forever, almost, so surely somebody has come up with the answer.

Any help would be *greatly* appreciated.


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I just squeezed my coil spring with a pair of pliers and slightly bent the striker spring. I’m sure that every gun is a little different than the next one. Mine had Slightly heavy pull but the biggest problem was it wasn’t smooth at all. Very gritty.Some people take a spring out of a ball point pen and cut it to length.You could try that and if it doesn’t work you still have your factory spring. They also make little thin plastic washers to keep any side plate out of the mechanism. I put a few of those in too.I went on eBay and looked up Benjamin parts.There’s a lot of aftermarket support for Crossman Benjamin.
 
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Ok, Don, and all those other fellow 397 / 392 shooters. I may have a solution, or at least something you might want to try, to improve your trigger.

All this talk got me working on this thing again. I spent more time polishing all the edges of the trigger, sear, the inside of both sides of the trigger assembly housing, and the face of the striker where it connects with the sear.

I used 220 grit wet/dry sandpaper, followed by some emery cloth. Some people like stones. I like sandpaper and emery cloth. To each his own. Same difference.

I highly recommend doing that.

Then, my wild, crazy idea that I came up with during all this was to take some plastic tubing, and slide it onto the front part of the sear, where it contacts the trigger itself. That, by itself, takes up some of that creep in the trigger. Be careful not to push it all the way to the back, or it may bind on the trigger assembly housing. The first time I did it, I ran into that.

Then I tried putting a washer between the trigger and the sear in that same location. That worked fine, except the washer would slide back sometimes and it locked up the trigger, until I pointed the rifle down and jiggled it, and it slid back forward again. I suppose you could superglue a washer to the trigger to take up the slack and it would do the same thing.

I also bent my sear spring just a little bit.

Then I gave my tubing idea another try, but this time I did not push it all the way back, and it works fine. I don't know how long it's going to last, but we will just have to wait and see about that.

Now, I have pretty much no creep whatsoever in my trigger. Just a nice, crisp pull. It's not light, but it's not unpleasant now, like it used to be.

We have an 11 year old boy in our church that comes here for services whenever his parents can bring him here. He likes going out on chipmunk patrol with me after lunch. I wanted to get this gun fixed up better for him to use, and to teach him how to shoot. And now, I think it's ready for him. I think the trigger is fine now, even for him.

Make sure you do a mallet test on yours if you try it. Mine passed it with no problem.

The plastic tubing also makes it butter smooth.

Have you ever had oxygen in a hospital or ambulance? I saved one of my sets of tubing from that, and used the small portion up by the the nose part of it. But you could probably find suitable tubing at your local hardware store, too, if you don't have any of that, or IV tubing.

Be sure you cut it close enough to the end of the sear that it doesn't bind on that end, either.

Don't be afraid to work on these things, either. If you lose any parts or mess anything up, you can always call Crosman at 585-657-6161 to order replacement parts for it. They've always had what I needed for next to nothing, they didn't gouge me with excessive shipping costs, and they've always given me some of the best customer service I've seen in these past ten years or so.

Here is what I believe to be the best YouTube video on how to take these rifles apart:

https://www.youtube.com/watch?v=M3xlS4f89QU

It doesn't cover opening up the trigger assembly housing; but that's small fry.

The only tricky part about the whole operation, as far as I am concerned, is that when you reassemble it, when you insert the striker into the tube and reattach the trigger assembly to the rest of the gun, you need to make sure you have the bolt in the raised position, like you are going to cock it. Or you won't be able to cock it. Apart from that, it's a piece of cake.

If you have any problems, you could also feel free to call me at 719-395-6395. Ask for Father Peter. Or if you don't want to call me "father", call me "Hieromonk Peter", "Peter", "that crazy old dumkopf that drives around in a golf cart shooting poor innocent little chipmunks," or whatever. I don't care what you call me. I'll be happy to try to help.

Disclaimer: I have lousy hearing, and telephones don't work very well for me. I might have to get somebody to translate for me. But I'll be happy to try to help. I've taken our 397PA apart many times.

Below is a picture with the tubing on it. You may have to zoom in on it to see it, as the tubing is clear.

I hope this helps.

Feedback appreciated.

And if any of you have other suggestions that you think may be helpful, I'd still like to hear them.

Cheers.

Stay healthy, and thank God for everything.

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Ok. Well, I put it through the ol' Aberdeen Proving Grounds trials, and while the tubing idea started out great, the trigger creep crept back in again after a while. Not all of it. It was still an improvement. But it warranted looking into.

So, I took it apart again and examined everything. The tubing was still in place, but had gotten squashed down a bit. Hence, some of the creep returning.

So, back to the drawing board...

I looked around and found some plastic squares with nails through them. See below. The plastic looks much tougher, so I went with it.

The first try helped, but didn't take enough of the creep out, so I added more plastic from the other direction. Now it works great.

Obviously, metal would work vastly better, but I'm working on a 0 budget, so we do what we can. I can look around for some metal later.

In any case, the concept is sound. Put something that doesn't bind in between the trigger and the sear in a way that they won't dislodge or shift in an unwanted position.

Again, make sure you give it the ol' mallet test, just for safety's sake.

I haven't had time to test it, and it's time for bed, but it's light and has zero creep, so something along these lines seems worth looking into.

I hope this helps someone.

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The biggest improvement to make in pull weight is not from swapping springs. It's changing the angle of the sear where it touches the hammer. When pulled, the trigger actually presses back on the hammer spring. So you are not only working against the heavy trigger spring, but also the heaviest spring in the gun, the hammer spring. Put the trigger together and watch the parts work, you'll see what I mean. This is actually a "feature" on most of the Crosman pumper guns. 

Make the sear surface more forward (like this: /)until the point where the hammer no longer moves backwards when the trigger is pulled. This should make a big difference. It won't make the gun unsafe unless you have the engagement set on the ragged edge to begin with. 

For the sear engagement, I drilled the front of the trigger blade, just where the front of the trigger (right above the finger curve) meets the clamshell. Thread this and install a set screw. You can then dial in the engagement by adjusting the screw out or in. Alternately, you could glue a flat shim there in the same place to accomplish the same thing. That way you don't have shims floating around in the working parts of the trigger to come loose. 

I had some pics floating around a long time ago on the web. Can't find em now. 
 
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The biggest improvement to make in pull weight is not from swapping springs. It's changing the angle of the sear where it touches the hammer. When pulled, the trigger actually presses back on the hammer spring. So you are not only working against the heavy trigger spring, but also the heaviest spring in the gun, the hammer spring. Put the trigger together and watch the parts work, you'll see what I mean. This is actually a "feature" on most of the Crosman pumper guns. 

Make the sear surface more forward (like this: /)until the point where the hammer no longer moves backwards when the trigger is pulled. This should make a big difference. It won't make the gun unsafe unless you have the engagement set on the ragged edge to begin with. 

For the sear engagement, I drilled the front of the trigger blade, just where the front of the trigger (right above the finger curve) meets the clamshell. Thread this and install a set screw. You can then dial in the engagement by adjusting the screw out or in. Alternately, you could glue a flat shim there in the same place to accomplish the same thing. That way you don't have shims floating around in the working parts of the trigger to come loose. 

I had some pics floating around a long time ago on the web. Can't find em now.
Click to expand...

There’s some Crosman guns that already have the holes drilled to put set screws in. But I couldn’t remember if my 397 had them or not. But yes that makes a big difference also. It seems like there’s a lot of people these days That want very light trigger pulls.I grew up on guns that had trigger pulls that averaged 4 pounds. So if I get one that has a 2 pound trigger pull I’m very happy.
 
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Well, I bought a SuperSear.

Thanks, @MileHighAirGunner for the links about it.

And thanks, @thumper, for your post as well. It was good information to know, and is much appreciated.

Although I hadn't given up on my efforts to improve the trigger as I'd been going about it, once I saw the SuperSear, I had to concede that it looked like a much better and more comprehensive solution than continuing to dink with the factory sear.

The sear came today. Although I had been a little apprehensive about grinding down the trigger stop post in the trigger housing to allow room for the SuperSear, it didn't turn out to be nearly as difficult as I had feared.

The SuperSear did need the face of the bearing surface polished, but that was only about a five minute job.

The rest of the installation went without a hitch.

So, what do I think of the SuperSear? Wow! GREAT!!!

I always thought the trigger of this 397PA was real cruddy. It wasn't the worst trigger I'd ever used, and I was able to adapt to it well enough; but I thought it was a real cruddy trigger.

Now, with the SuperSear, it has an amazing trigger. It is on par with our Weihrauch HW97K's Rekord trigger, in how it feels. And I'm not exaggerating. It's turned this air rifle into a joy to shoot. It's like a whole different gun. It makes for a much, much better shooting experience.

I will say I'm not without some trepidations about wholeheartedly recommending it because, apparently, they changed the production of it from hardened steel to aluminum, with a hardened steel pin on the bearing surface of the sear. In that blog that @MileHighAirGunner posted the link to, somebody was asking about whether they've seen any unusual wear because of that. AOA replied that they'd sold them like that for over a year and hadn't had any complaints.

I fired our 397PA around a hundred times today, and then took it apart and inspected it for wear. There was some wear of the aluminum around the pin, but the pin itself looked ok. And I did feel that it felt a little squirrelly to shoot for about the first 20 pellets, and then settled down to its nice sweet pull. I think it was then that the aluminum wore away.

I wish they would have kept to an all steel sear. I'll check this periodically for a while. Hopefully that was just a normal breaking in period for it.

Apart from that, though, I highly recommend it.


 
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