Pump-Assist Benjamin 392: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

Pump-Assist Benjamin 392
The Benjamin 392 pump assist is an interesting side street in the hobby.

Part 1

A history of airguns

This report covers:

  • Pump-assist pump effort
  • Sheridan Blue Streak pump effort
  • How it feels
  • Velocity test 1
  • Velocity test 2
  • Velocity test 3
  • Velocity test 4
  • Velocity test 5
  • Trigger pull
  • Conclusion

Today we look at velocity and some other things that relate to the pump mechanism of the pump-assist Benjamin 392. We will start with the effort to pump the gun.

Pump-assist pump effort

In the past I have used the chart supplied by the pump-assist manufacturer, Bob Moss, to show the pump effort of the pump-assist Benjamin 392. Today I actually tested it, by pumping the gun on my bathroom scale. I know an analog spring bathroom scale is not an accurate test instrument, but it should give us a basis for comparison, because I will also measure my recently rebuilt Sheridan Blue Streak.

I laid a thick book on the scale and pressed down on the book with the pump handle for each pump stroke. I did discover that if I went too slow the pump effort remained very low, because air was not being pumped into the reservoir. So I pumped each stroke as fast as normal and them shot the gun to verify that it was filled. I have subtracted the weight of the book (2 lbs.) from these numbers.

Pump stroke…………..Effort in lbs.
1………………………………….11
2………………………………….16
3………………………………….13
4………………………………….15
5………………………………….15
6………………………………….15
7………………………………….15
8………………………………….14

After verifying the gun was full, I then pumped it as fast as I could this way. The scale needle never went above 20 lbs., and 2 lbs. of that still has to be subtracted for the weight of the book.

Sheridan Blue Streak pump effort

Next, I tested my recently rebuilt Sheridan Blue Streak the same way. We know from recent velocity testing that this rifle is on spec. for power.

Pump stroke…………..Effort in lbs.
1………………………………….13
2………………………………….27
3………………………………….33
4………………………………….36
5………………………………….40
6………………………………….40
7………………………………….42
8………………………………….42

There you have it. I would say those numbers accurately reflect the difference in effort for the pump-assist rifle and the Blue Streak. Until you try it the first time it is impossible to imagine — particularly if you are a veteran multi-pump shooter. Fred — you now own Mac’s pump-assist (and mine before he got it). What’s your take?

How it feels

I don’t have that video of my pumping the rifle ready for you today, so I will describe how it feels. Initially the pump effort is very easy, but somewhere in the middle of the stroke the effort goes up to the maximum. It stays there for an instant then drops back to almost nothing as the stroke is completed. The peaks are the efforts listed above.

I watched the pump piston head while I was pumping and discovered that the peak effort comes as the pump head is almost home, which is what you would expect. The pump-assist mechanism changes where in the stroke this happens, because as I reported in Part 1, the fulcrum changes as the number of pumps increases. Now, let’s look at the power of the rifle.

Velocity test 1

First I want to establish the velocity of this rifle on a varying number of pump strokes. The 392 manual says to use a minimum of two pump strokes, and not to exceed eight strokes. From experience I have decided that three strokes is a better minimum. Maybe that was the recommended minimum at some time in the past, or maybe I had a bad experience with fewer pump strokes, but three is the fewest number of strokes I will use. Here is the velocity of the gun with Crosman Premier pellets on a varying number of pump strokes.

Pump stroke…………..Velocity f.p.s.
3…………………………..451
4…………………………..494
5…………………………..535
6…………………………..567
7…………………………..585
8…………………………..608

That’s right where I expected it to be. It seems to be functioning like a new gun. At the maximum velocity this rifle generates 11.74 foot-pounds of muzzle energy. I have seen 392s go from 11 to almost 14 foot-pounds with Crosman Premiers, so this one is on the low end of normal. Just for fun I went back to Part 2 of the test I did on this rifle back in November of 2007. At that time 5 strokes got me 509 f.p.s. and 8 strokes got 589 f.p.s. Things are pretty much where they were back then, if not a little better.

Velocity test 2

In this test, I first oiled the pump piston head. I noted that the pump head was oily when I did this, so I doubted there would be any change, but sometimes people wonder if the gun was given a fair chance to do its best. So I oiled it. Here are the results. I’m still shooting Premiers in this test.

Pump stroke…………..Velocity f.p.s.
5…………………………..508/535
8…………………………..594

Notice that my first shot on 5 pumps was slow. That often happens right after you oil a pneumatic. Then the speed increases as the oil gets distributed around the pump head. That’s why I shot a second time.

Velocity test 3

This test was for the stability of the gun with a certain number of pump strokes. I tried it with 5.

Shot…………..Velocity f.p.s.
1…………………..536
2…………………..537 (fastest)
3…………………..531
4…………………..530
5…………………..534
6…………………..529
7…………………..526 (slowest)
8…………………..533
9…………………..527
10……… …………534

The average for 10 shots was 532 f.p.s. The maximum spread was 11 f.p.s. That means the 392 pump-assist is pretty stable.

Velocity test 4

Now it was time to try the rifle with some different pellets. Because this is a pneumatics, it’s going to become more powerful as the weight of the pellet increases. First up was the H&N Baracuda Match with 5.51mm heads.

Pump stroke…………..Velocity f.p.s.
3…………………………..390
5…………………………..464
8…………………………..523

On 8 pumps the rifle develops 12.82 foot-pounds with this pellet. That’s plenty of power for hunting, and of course the 392 is a .22 caliber airgun, after all.

Velocity test 5

In this test I shot the lighter JSB Exact Jumbo Heavy that still weighs 18.1 grains in .22 caliber. Even though it’s lighter than the Baracudas, it’s still considered a heavy pellet. They gave me these velocities.

Pump stroke…………..Velocity f.p.s.
3…………………………..416
5…………………………..492
8…………………………..558

On 8 pumps this pellet delivers 12.52 foot-pounds at the muzzle. It’s another good performer for hunters.

Trigger pull

This is a new 392 so the trigger is not like the one in my Blue Streak. The 2-stage trigger broke at 5 lbs. 9 oz., which is not exactly light.

Conclusion

I tested the pump-assist Benjamin 392 multi pump several different ways and learned that it is still performing like new. And, this was the first time I tested the actual pump effort. My test was simple, but the results are similar to the chart the maker gave me.

The pump-assist Benjamin 392 was a wonderful idea that was never fully realized. If it had migrated to the hand pump, the world of PCPs would have changed, in my opinion. We may never know, but I know I own a remarkable invention that few airgunners will ever get to appreciate.

59 thoughts on “Pump-Assist Benjamin 392: Part 2

  1. Very cool.
    As a person that grew up pumping a Benjamin 312, and later 3xx models, anything that would reduce the ever increasing pump effort is a boon to a pumper shooter.

    But even having used them over the decades, I just can’t wrap my brain around the automatic moveable fulcrum.
    That’s why I asked to see a video of it in action.

    On a side note, I recently picked up a 1953 Benjamin 252 .22 pistol that uses 8gram co2 cartridges.

    It is loads of fun, and quite small compared to the newer guns that use the 12 gram cartridges.


  2. Pingback: Pump-Assist Benjamin 392: Part 2 | Airguns: Air Rifles and Pistols

  3. BB,

    Being a hand pumper, I can certainly appreciate anything to make filling these things easier. Filling rifles like an Edge is not so bad, but when you shoot and repeatedly fill a big bore for an afternoon, you know you have had your workout for the day.



      • Chris,

        Actually, I have not had much time to play with it since I bought it. I have mounted it on my HM1000X, but have not had a chance to zero it in yet. Life has kept me pretty busy for about two months now. I am hoping things will slow down a bit, maybe in January.

        As for the bubble level, I think it is awesome. I previously owned a Sun Optics 6-24X56 that had a bubble level in it. I did not care for the optics, but I really liked the bubble level. This new scope has both clear optics and a bubble level. I would like to see bubble levels in the smaller scopes if possible.



  4. B.B.,

    Nice testing. This definitely belongs in the history section. Too bad it never took off. It was cool to see you verify the pumping as well. As a kid,.. now 55,.. I do not remember ever seeing one in life or print. I am sure they were there. The lever actions were my “lust after” choice for some reason.

    By the way,… the link at the top for Part 1 does not work. It pulls up “page not found”.

    As a complete aside,… I set up the indoor 41 ft. range last night and promptly gave it a quick test with the TX and LGU. 10 shots each and the holes at the target barely grew at all. I really was not even trying. Very cool. At that point I looked back at my targets from 2 years (Jan. ’15) ago when I first got the TX. 1″ and sometimes worse was the norm. 4 months later, 1/2″ was closer to the norm. Now,.. almost true 1 hole groups with a random brand from the .22 pellet selection. I thought that was kind of a cool look down “memory lane”. 🙂

    Oh yea,…. 0 degree’s F here. (Just to let all you in the warmer climates know as to just how good you have it)

    Chris



  5. Chis,
    I feel your pain:):),
    With all that pumping going on it’s easy to remember why California called all those years ago. The problem is, of course, one gets old and weak and even a outside temp of 40 degrees makes one shiver. Fortunately I write beneath a pile of gently snoring terriers and everyone is happy.
    Sure am glad I’m not living in a cardboard box underneath a bridge somewhere though.
    ‘Tiz the time of year one should really appreciate the largesse one has.
    One of the terriers still is pining for his lack of opposed thumbs. He’d really like a set in his sock this year but then we’d have to hide the car keys or the SUV would be gone and we’d be getting calls from the Highway Patrol.
    (“Sorry to bother you Sir, but are you by chance missing a SUV and a small terrier…? And a credit card…? If he’d been tall enough to reach the slot in the gas pump, we’d never have caught him…”)
    I seem to remember Cousin John Dean teaching me some basic skills with a Benjamin out in the barn. But when there, we discovered a distinct lack of any …unwanted…critters. Either they got smarter or we got dumber, Probably the the later, or the former, or both…
    So he taught my little 8 year old self how to drive a tractor instead.
    Not a bad trade-off and earned me major bragging rights in grade school.
    Actually, still got the bragging rights as, in this part of the 21st century, few of my acquaintances know even the sharp end of a John Deere.
    (Hint: When dealing with tractors, EVERY END is a sharp end.)
    But that pellet shooter was way accurate with the only drawback of being mighty sweaty pumping in a Nebraska August.
    (I start sweating even writing that.)


    • David,

      Who knew you drove a Johnny Popper? My favorite type, along with Farmall.

      I’d give up one opposable thumb for an unstyled B. But I digress. And I don’t have stockings big enough to even fit one with a Rollomatic front wheel, to say nothing of the high wide one I really want.

      I once flipped a Wheel Horse backwards by running the front end up a tree while mowing the lawn, but I’m not quick enough to get off a Fordson when it hits a rock while plowing.

      Merry Christmas,

      B.B.



      • BB,
        We didn’t have all that many trees in central Nebraska, despite the appellation of “A Girl Behind Every Tree.”
        Turns out, there weren’t no trees.
        The tractor was not the classic “Johny pop-pop” but a much smaller Ford, and very adept. Just the thing for an 8 year old to terrorize small chickens and medium sized cattle. At least until Uncle Vincent caught you doing it and Cousin John Dean for teaching you how. We’re both in our 70’s now and still hearing about it.
        Even we “City Kids” got basic training on tractor safety…just in case. Seriously, along with “Blood on the Asphalt” in Driver’s Ed, I still remember “Stupid Stuff Not To Do With Your New Tractor.”
        Of course none of which can match the contrived stupidity of unsupervised drunken farm kids on the Great Plains.
        I know, I used to be one.
        (The “How not to water-ski while being towed by a pickup truck in an irrigation ditch” will have to wait for another day. But I do have pictures.)



          • As an eight year old, and 60 + years having passed, I can’t say for sure. But I’m ‘gonna guess a 9N. The more I think about it the more sure I am. Pale gray with red trim and a hand throttle that I found…entertaining.
            I’d love to have one now.
            With our current 60 x 60 backyard, might be overkill, though. Especially living in the Bay Area. Getting it in, getting it out, probably need a municipal permit every time.
            But now you mention it…now that I think about it…bordering a regional park and all…hmmm…


          • All this tractor talk makes me nostalgic. I never owned a tractor. But 51 years ago I was an English major at the University of California-Davis campus. I was afraid that my major was unemployable, so I enrolled in a tractor/farm implement class at the agriculture school there. My plan was to get a useful practical skill. Our tractors were all old, donated by people to the University when their useful life was up. I remember a Cat D4 that had been converted to run kerosene–it came from Alaska, where kerosine was the only fuel widely available. And an International TD9 that used gasoline to start, then you pulled a big lever that changed the compression ratio and hit the diesel throttle, and if you were lucky it ran on diesel. And finally, there was a three-wheel John Deere, two cylinder gas engine that idled at about 150 rpm. The front wheel would just skid if you tried to make a sharp turn with the wheel. You had to use the rear wheel brakes, which braked each wheel independently, to make a sharp turn. The brakes were strictly mechanical, no hydraulics, so you rally had to stand on the pedal to get any effect. A really strong person could turn it in its own length.

            For our final exam, the class was divided in to small groups, and each group got a tractor. We had 10 minutes to sabotage our tractor. Then we traded tractors. First group to get their tractor running again got the A!

            As it turned out, I got a job when I graduated, so I never used my tractor skills.


            • CC. BB,
              Wow, you’re way beyond me in tractor expertise.
              But I can still impress my longtime sweetie by a surprise education on loading/unloading M48 Main Battle Tanks from WW2 Victory Ships. (WWII ship, not WWII tank.)
              I didn’t even remember I remembered this until this silly bit of personal history came out. ‘Twas almost a cold comment, but went something like, “How the hell do you remember stuff like this?
              An interesting story in itself, for another day, but I’ll assume Naha harbor is still there and were Mom (the decorated Okinawa Combat Nurse) still with us She’d verify.


              • Hey, 103David,

                Naha harbor is still there, I visited a few years ago to see the war memorial. My father’s ship landed troops for the invasion of Okinawa, and the memorial is very moving.

                Also on the beach at Naha I noted a sign that said “when you are stung by a jellyfish, go immediately to the emergency room.”

                Not IF you are stung, but WHEN. I didn’t swim.

                Flintrocker



  6. B.B.,

    Your findings regarding pumping effort vs. the conventional Streak are stunning. (Perhaps the bar graphs you put in #1 just didn’t register enough with me at the time.) The Streak requires something like an average of 34 pounds of effort per stroke while the Benjy pump-assist averages just a bit over 14. I am so accustomed to reading of modest differences in measurements between rifles, pellets, and so on, that those figures impress me no end.

    Your results also got me to wondering (and wandering, as my mind often does). In Part #1 you wrote that folks went “ballistic” at the proposed MSRP for one of these had Crosman gone for it. How wrong they were to react that way! How much more than that do people regularly pay for entry-level PCPs with a tank?

    I would pay a LOT more for a pump-assist Benjamin than I would a regular 392.

    Michael

    Michael


    • Michael,

      I hope Fred, who used to live in the People’s Republik of New Jersey, sees this report. He traded with Mac for a pump-assist that Mac got from me, and he is the only other person I know who owns one. He can tell you whether I’m telling the truth or not.

      Don’t be too hard on the people who refused to pay, though. Until you pump one of these you absolutely cannot believe how much easier it is, and it never gets harder! That’s why I will hold onto mine.

      And that is why I think the butterfly hand pump could sell at $300+, even with $500 booster compressors and $1,000 stand-alones. Sometimes a guy wants just the minimum of equipment with him, and the butterfly would enable a 12-year-old to pump to 3,000 psi.

      B.,B.


      • Michael,

        I thought the same thing as you said there towards the end. I think the idea needs revisited especially since the population is getting older and like you pointed out,…. look what people are spending these days on air guns and related products. Plus,.. the 392 seems to have an iconic following. Not to mention the hand pump benefits. It seems like a no-brainer. I mean really,…. who does not like easier?


        • Chris,

          “Who does not like easier?” You’re right, of course. Everybody should prefer easier. That IS a no-brainer. Unfortunately, a lot of folks seem not to have brains. ;^) Some people seem to feel that easier is somehow cheating.

          When I briefly roadied there was a saying: “Never carry what you can roll, and never work quickly when you’re paid by the hour.”

          Michael


      • B.B.,

        I’m with you on all of this. I would have paid much more than $300 for a nice new Butterfly pump. I’d probably pay more than $300 for one of the Pump-assist 392s out there.

        If a guy could pump up a multi-pumper as easily as the Pump-Assist, he might not even feel the need for a PCP at all, especially if he can have the stock trigger improved.

        Incidentally, Mac1 does offer a special treatment on multi-pumpers, although Tim cautioned me that it is only appropriate for folks with VERY long arms. (I have the arms of a silverback gorilla, so I qualify.) He can do what he calls an extended billet. He does woodwork on the stock piece under the action and on the forearm. Essentially the lever is made two or so inches longer, putting the “cut” closer to the triggerguard. If your wingspan can handle it, that extra lever length makes about as much difference as you can imagine — a LOT.

        Michael


      • Could they have combined the pump assist with the steroid modification. Then you would have had the equivalent of a Sharp Ace with a better trigger. Make it scope friendly and I would buy one of those for sure.


        • Brent,

          The extended billet might be possible, but why bother if it is already that easy to pump?

          As for the power mod, I would be worried that the additional metalwork and joints might not be able to handle the extra stress. I seem to recall with certain years/models of Benjamins and Streaks Tim recommends replacing some of the steel with stouter stuff .

          That suggests to me that in handling the extra pumps a Steroid allows the shooter, the machinery is stressed much more. To borrow a phrase, I suspect the Pump-Assist Benjamin was built for comfort, not speed. While a Steroid provides additional power at every pum,p level over a stock air rifle, the real reason to get one is to be able to pump it 12 – 14 times and actually get nearly 25 foot pounds out of it.

          Additionally, Tim does a highly regarded trigger tune, and he also offers other options such as dovetail grooves for a scope.

          Michael


  7. I noticed that the 392 shoots about like a Diana model 27 when pumped 3 times. 3 or 4 pumps would be enough gun for most of my needs. The pump assist comes into play on the uper end so it depends how you plan to use it. Still to bad the assist did not make the market.




    • 103David,

      You caught that! Yep.

      My wife saw it / participated once a week every week for the four years she was in college, so if I loved her, I had to be able to enjoy it and learn the language.

      It also comes in handy for the fifteen minutes we spend on cult cinema in my History of Film class. Each year I find clips from it have less and less shock value, which is good, but also too bad. In general I like to see discomfort among those who are easily made uncomfortable.

      Hmmm. Now that I think about it, I wonder if my wife still has her Magenta outfit!

      Michael


  8. Hey B.B.,…. Ol’ Buddy,….. Ol’ Pal,…….

    That most AWESOME contest that P.A. had running was over at 3 AM this morning. So,…. I was thinking,….. seeing as how you are tight with P.A.,… I figured maybe that you could call them up and see if any of the names are anything that you recognize? I am sure a few readers are waiting with their fingers crossed. 🙂 Pleeeese,… 😉

    Ok,… joking aside,…. (ok,… I am not actually joking),…… that was one heck of a give away!! I do not recall them doing that before. That was very substantial in my opinion. The odds had to be pretty decent as well. I wonder how many entries there actually was?

    As a side,… I would be interested in hearing what others put on their list. Mine?,….. Texan, Condor, S 510 Ult. Sprtr., Maximus and a couple of scopes. Just imagine,…….. 🙂

    Chris


  9. BB,

    First, I NEVER miss a blog. I’m in Roanoke right now, just got here from NJ on the way to GA. The 392 is on a moving truck with the rest of the collection. Not only is the pump assist 392 rediculously easy to pump, at roughly 10 yards it’s satisfyingly accurate. No plans to sell it for quite some time. Sure, it’s pricey but it’s also rare and very neat.

    Fred DPRoNJ




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