Benjamin 700 multi-pump repeater: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

A history of airguns

Part 1

Benjamin 700
Benjamin 700 repeating BB gun.
This report covers:

  • How do they do it?
  • BB………….average diameter
  • Repeater
  • First test
  • Second test
  • Discussion
  • Next test — lead shot
  • Trigger pull
  • Safety
  • Summary

Today is Part 2 of the Benjamin 700 test and Part 2 is usually a velocity test. I will do that, but the nature of this very different multi-pump presents some interesting challenges. The biggest of these is the fact that this gun was designed to shoot more than one shot per fill. That puts several wrinkles into the test.

How do they do it?

To understand what I am up against you have to understand how a multi-pump pneumatic gun is able to get several shots on a single fill. Someone once told me that these Benjamins must have a small reservoir attached under the stock, and that is where they store the extra air. Without thinking about it, I assumed that was true, but it’s not on this gun. Nor does it need to be. ANY multi-pump air rifle or pistol can be set up to get multiple shots from a fill of air!

To get a multi-pump to shoot multiple shots on a fill, the valve closure spring has to be set to close before all the air has escaped from the gun’s reservoir. The weight of the striker and the strength of the striker spring also need to be changed. That is a balancing act, because it can also make the gun unable to function under certain circumstances. The air transfer port size is another factor to be considered.

You could take a stock Benjamin 392 right now and change these things to get the rifle to shoot multiple shots on one fill. But the number of pump strokes needed to fill the gun might also change. And the number of shots you get might not be that many. To get the most effective velocity and number of shots would require a lot of careful tweaking of the firing valve, the weight of the striker and the strength of the striker spring as well as the diameter and length of the air transfer port.

Are you starting to see why I said this test has to be different? Normally I would pump the gun 2 to maybe 8 times and test the velocity at each stop. What will this gun do if I do that? Well, let’s see. I will shoot a steel BB, so the first job is to find which BB is the largest, because this Benjamin wants a 0.175-inch BB.

BB………….average diameter

Daisy………………..0.173”
Hornady…………….0.1725”
Air Venturi Steel……0.1725”
Dust Devils…………0.165” – 0.172”
ASG Blaster………..0.1735”
Avanti Match shot….0.1735”

First test

I decided to use the Avanti Match Grade shot because they were the most uniform of the two largest BBs. Let’s see how they did.

Pumps…………Velocity………Air remaining?
2…………………229…………Didn’t check. See text.
3…………………365
4…………………438
5…………………509

At this point in the test I noticed that the pumps were getting much harder. That was because there was air remaining in the gun. I couldn’t test for that (yet), because each time I cocked the gun it shot a BB. I felt stupid when I realized how this design had to work! So, I pumped the gun 5 more strokes after the last shot, with air remaining in the gun before I pumped it, and look what happened.

Pumps…………Velocity
5…………………531, 478

I shot a second time and got good velocity! There was even more air left in the gun, but not that much. That established 5 strokes as the lowest number of strokes I could pump and still have some air remaining after the first shot. So, for fun I tried something. I pumped the gun 8 times, fired a shot then pumped it again. Let’s look at what happened, then I will explain it.

Pumps…………Velocity
8……………………511
1 pump more……..477
2 pumps more……468

I was testing what Benjamin said about maintaining the velocity by pumping 1 or 2 strokes after each shot. But this test was inconclusive. I will run it again in a different way.

Second test

I next tried pumping the gun 10 times to see what happened. Before starting this test all the remaining air was exhausted. The Benjamin manual said to pump the gun 10 to 12 times and 4 to 5 powerful shots would be available. I will tell you why I didn’t pump the gun 12 times in a moment. For now, let’s look at what it did on 10 pumps.

Pumps…………Velocity
10………………514, 454, 356, 20 f.p.s. (maybe)

This time I got three shots that sounded powerful, with the velocity decreasing on each shot. The last shot didn’t register on the chronograph but I could tell it was very weak. That last velocity is just a guess. The BB went slow enough to see and had a pronounced arc to its flight of 3 feet.

Discussion

Now we see how this design works. Honestly, it works better than I expected. I’m sure you are wondering why I didn’t pump it 12 times instead of just 10, so let’s talk about that. Until you have shot one of these front-pump Benjamins, you have no concept of how hard they are to pump. So, I’m going to show you.

I use an analog bathroom scale to measure the weight or resistance of a pump stroke. This is the kind of scale that has a spring inside to provide resistance. It’s not that accurate, but it’s close enough. I’ve used the same scale for all my writing career, so what you are about to see can be related to all my past tests. I put the mushroom-shaped pump rod end on the scale and press down until I hear the gun’s intake valve pop open to accept the air. I can hear it on every pump. Here goes.

Pumps…………Effort in pounds
1…………………..30
2…………………..48
3…………………..68
4…………………..87
5…………………104
6…………………118
7…………………130
8…………………150
9…………………152? stopped

After 8 pumps the pump rod started coming back out of the gun after the pump was finished. That either means there is air that didn’t go into the gun or air is escaping from the gun. I think it is the former. This is very common with front-pumpers.

Now you see what I am up against to test this airgun. It isn’t easy! I push on the back of the receiver tube with my left hand and on the stock with my right hand. Pushing just on the stock would put too much of a strain on it, I believe. Not many children could pump the gun this many times. And I am not going to try 12 pumps because it seems like even 10 are too many.

Next test — lead shot

I know that 8 pumps gets the gun up to maximum power with air left over, so that’s what I am going to do. I have a tube of vintage Remington lead Air Rifle Shot that measures 0.175-inches in diameter, so I will pump the gun 8 times, shoot it and then pump it more times before shooting again. I will do this a couple times to see what happens.

Pumps…………Velocity
8……………………482
2 pumps more……417
2 pumps more……409
3 pumps more……440
3 pumps more……458

It looks like there is a balancing act for my gun and I haven’t quite found it yet. But I’m close. On the last shot the pump rod started coming out of the gun again, so the gun was over-charged once again — at least by my definition. That means I probably should try fewer pumps to start with. Maybe 5 pumps is best.

Obviously the lead balls weigh more than steel BBs and will go slower. But they also fit the bore better, so the air loss isn’t that great. The gun’s maximum velocity recorded with a steel BB in today’s testing was 531 f.p.s. At that velocity a 5.1-grain BB generates 3.19 foot pounds. The lead Air Rifle Shot weighs an average 7.9 grains and generates 4.08 foot-pounds at the peak velocity of 482 f.p.s.

I have ordered 1000 rounds of 4.45mm (.1752-inches in diameter) lead balls for further testing. I don’t especially want to shoot up my vintage shot, as it is collectible.

Trigger pull

Remember that “hair trigger?” Let’s see what it really is. My electronic scale measures the single-stage let off at 1 lbs. 11 oz.

Safety

The safety on the Benjamin 700 is strange. It is a small button on the right side of the receiver. It can only be applied when the gun is cocked. If you pull the trigger with the safety on the striker does go forward, so to take the safety off again the action must be recocked.

Benjamin 700 safety
The safety is that round button. When the gun is cocked push it down for safe.

Summary

You have just had a look at the operation of a very strange airgun. It will be fun to learn how accurate it really is, so stay tuned.

56 thoughts on “Benjamin 700 multi-pump repeater: Part 2

  1. B.B.,
    It would be nice to see if actual BB size shotgun shot (.180″) helped the accuracy of this gun, but I guess it wouldn’t feed through the mechanism; I guess you could only do that with the single-shot version (model 300?).
    take care,
    dave


  2. B.B.,

    So this 700 is really like a PCP and you need to find the precharge that allows the valve to retain the right amount of charge and then you need to find the correct number of make-up strokes to keep it balanced…WOW! That might be good for a very few follow up shots but would be amazing for a consistent string of more than four or five.
    Cool concept using early Twentieth Century technology. That concept might be doable with an electronic valve in the Twentyfirst!

    One last item. It is a smoothbore barrel…yes?

    Enjoy the new week!
    Shoot CLEAN! or go home

    shootski


    • Shootski
      And a better pumping mechanism.

      Somebody will get wore out quick with this gun.

      Then next thing is it accurate enough to be worthwhile for all that pumping.

      Like I said. Cool gun. But sounds like more work than what it’s worth.

      I think the modern 392 Air Conserving Pumper would be the way to go now days in more ways than one.



        • RR
          Well you know how that goes.

          I’m thinking probably so.

          Just got to spend time with it to see how it goes.

          Now that would be something that should of been done somewhere throughout time.



            • RR
              That’s the way I keep feeling.

              But I don’t like the brass barrel. Is it hard brass or soft brass?

              And then the scope mounting of the 392 and 397 series. I can do open sights now pretty good. But it’s always nice to be able to mount a scope.



                • RidgeRunner,

                  I’ve looked at that optics mount with curiosity. Might it still pose the risk of causing separation of the weld as do the older, barrel-mounted clamps?

                  Michael


                  • Michael,

                    I will not say there is not risk there, but it is less likely to be an issue when mounted on the receiver. There is also another type put out by another company that I think is better, but I will not point to it here.


                • RR
                  You can get a 392 or 397 through PA with a scope and mount combo that mounts right to the receiver.

                  And I have teyed the mounts that clamp on the barrel. They are not very secure.

                  My concern is with the brass barrel is how long will it take to wear the rifling.


                  • GF1,

                    I seriously doubt you will ever shoot the rifling out of one, even if it was your only air rifle. These have been around for a long time and I have never heard of such.


                    • RR
                      I never said shooting the rifling out. I said wearing it out.

                      As in how much wear before there is a accuracy change.


                  • GF1,

                    I think the barrel is actually bronze. Unless you use hard pellets like Crosman, I really do not think you will have to worry about it for the rest of your life.

                    Now after a bit your accuracy may actually improve as the bore “smoothes” a bit and cleans out the manufacturing gunk. Then you might notice a POI shift.

                    If I did not already have the Crosman 101 I would go for that customized 392 in a heartbeat. I almost bought one when I bought my first air rifle. It was that or the Gamo CFX. Upon reflection I would get the 392.

                    I will make you a deal. If you get that custom 392 and do not like it, we will work something out on it.


                    • RR
                      Maybe so on the barrel being bronze. And only way to know how it does would be to own one for a long time and keep targets and reference back to them as time goes.

                      And I would like one of the ACP 392’s also. Problem is I have more wants then money.


  3. B.B.,

    I don’t suppose you can show a picture of how you pump this gun? Is one end on the floor as you press the handle back in? How long is the stroke? How big is the lower tube?

    Siraniko


  4. B.B.,

    Very interesting indeed. Thank you for all of the hard work that went into this.

    It looks like the .1752″ shot with 8,3,3,3,3 might get you a fairly consistent fps.

    The trigger blade is interesting with it’s 90 degree twist to turn the blade flat to the finger.

    Thank you for confirming that this could be done today. The method/variables you described are just what I had imagined. Once done though, it would make a nice multi pump. With single load pellets and rifled, even better. I have found the pump lever on an 880 to very ergonomic. That is one they got right and the 880 has really nice looks. Maybe why it has been around so long.

    Looking forwards to the accuracy phase.

    Good day to you and to all,…. Chris


    • Chris USA,

      There are Youtube videos that show how to do this to Benji 392s, as BB described. They call it the “air conserving” mod. It seems like a long project.

      Half


      • Halfstep
        There’s aplace on the left coast that sells them already all done up. That’s the 392. They coat more. But it will s what it is.

        I too many times keep wanting to pull the trigger on one. Pun intended as it goes.

        But other guns and air gun things keep getting my interest.


        • Gunfun1,

          There are either two ways to set it up or two different model choices. One way is 8 pumps, full power shot, 3 more pumps, another full power shot, and so on. The other way is 8 pumps, three medium power shots, 5 more pumps, 3 more medium shots, and so on.

          The fellow who came up with it, as I have read, is named Steve Woodward.

          Michael


          • Michael
            Yep I posted about the ACP 392 in the past.

            And I believe there is only one model made now. It is updated with some additional features compared to the original.



    • “The trigger blade is interesting with it’s 90 degree twist to turn the blade flat to the finger.”

      Chris, I have seen this before in old .410 single-shot bolt action shotguns from the 50s. =>


    • Chris,

      I have a newer plastic 880 and an older metal action one. I would rather pump an 880 10 times than a Benjamin or Sheridan 4 times.

      That said, even my older metal 880 is not nearly as well-made or as accurate as my 1960s Sheridan. It is pretty nice, though. If a really nice brass rifled barrel could be inserted into an 880, that would be one sweet shooter.

      Michael

      Michael


      • Michael,

        Yeah,.. they did the 880 right. If there is one cheap model that they could give a (serious) upgrade to,.. that would certainly be my first choice. I mean heck,… look how long it has been around? It did not live that long for no reason. Me? I say it is time to give the classic 880 and nice upgrade.

        Chris


        • Chris,

          There are some differently-branded air long guns (don’t know if they’re rifled or not) with black plastic thumbhole stocks that are clearly Model 880s underneath, but they are hardly upgrades.

          I agree. A souped up, in the right ways, 880 would be really nice. In addition to a quality barrel, I could see having a longer lever that is hinged farther out, has a greater arc, and compresses more air with the same effort (or lack thereof, as the 880 is so easy-pumping). Then two or three shots on a full pump would be possible, or decent plinking power with just two pumps.

          Michael



            • Michael,

              Yeah,.. it is probably too much to ask. I was not aware that there were faux upgrades out there. I do not follow that line much. Yes, barrel, metal receiver, a real bolt,… a nice tight one!, peeps?, good syn. stock, better trigger, even adjustable for pull weight. But,… do it (right), or do not do it. I would go 150-200 for a nice accurate one, done right. Toss in some cheap plastic butt pad shims for LOP. Enough for +1″. Good dovetail.

              Oh yeah,… open that %$& load trough/port up!!!!!! 😉 3/4″-1″ would be awesome.

              A well balanced multi-shot valve would be icing on the cake with only 1-3 pumps needed to keep the fps the same. I would even settle for .177 and single shot.

              Chris


  5. BB
    Man that gun would be a workout to shoot. It looks like it can be as hard to pump as a PCP hand pump. Maybe even worse since no good way to hold the gun gun for leverage when pumping it.

    I think I would be only pumping 2 or 3 pumps at the most if I owned one.

    It is a interesting gun. But not for me I’m thinking.


  6. BB,

    I had not thought about it previously, but I can see why Benjamin went away from the plunger to the mechanical advantage of the lever. I can see kids pressing the plunger head against trees, etc. and pushing for all they are worth. I can also see bent plunger rods. I am certain that was the fate of many of these.

    I would not mind if a working 300 series was to decide to reside at RidgeRunner’s Home For Wayward Airguns.




  7. BB,

    Could anyone weighing less than 200# even pump this thing up to 10? I’m with Siraniko, I’d like the see a photo of the pumping technique.

    Are the lead balls you ordered just the “safe” lead bbs or are they something special?

    Half


  8. Thanks B.B.!

    Love the blogs that analyze the workings of a gun and how to optimize the performance.

    The safety is different on this rifle but I like the way it works. The HW100 safety can only be engaged when the rifle is cocked and that is sometimes viewed that as a negative thing. I find it to be an excellent feature – being a 14-shot repeater with a smooth side lever it is so quick and easy to chamber the next shot and thumb the safety ON that I often do it automatically. Its nice to have an indicator (after checking the spotting scope or resetting targets or some other distraction) whether the rifle has already been cocked or not.

    Happy Monday!
    Hank


  9. Modern multi-pump repeater.

    If you cut the pumping effort in half by using a lever, quadruple the number of shots available, double the velocity with a dual power option, switch to a shrouded rifled barrel for better accuracy, add a multi-shot removable side lever actuated pellet magazine, add a pressure gage, better trigger, sights, a dovetail for mounting optics, and put it in an all weather stock with a rubber but pad, you would have a modern version of this. The Nova Freedom rifle !



    • RR,

      Not only did I not do a comparison test with the IZHG 46, I promised a reader back in 2008 that I would.

      From reading the last report it isn’t clear that I meant to write a test, but the title certainly suggests that I did. And now you can’t buy the IZH 46M in the U.S. any longer.

      Should I do it anyway?

      B.B.


      • B.B.,

        How about a compromise and shoot the Gamo Compact and an Avanti 747? I have one of each and would be interested in seeing the results. (No, a test by me would be meaningless. Even with it rested I am a terrible shot with a pistol. If nothing else, I would be too embarrassed to share photos of the “groups.”)

        Michael


      • BB,

        I see used ones for sale all the time, some still new in the box.

        A blast from the past would be good, most especially for those thinking of accurate pistols.


  10. Everyone,

    I just watched a very nice video explaining BKL scope rings. I have the BKL adjustable mount that B.B. installed on the Diana 34P for me last summer when he reviewed it. I also purchased BKL offset rings to mount a UTG compact scope on my Gamo Urban. Normal rings did not allow proper eye relief due to the short tube length of the compact scope. These offset rings were just what I needed. Also, I didn’t know, but BKL has a little level that will screw into the threaded spreader hole in the ring and make a very compact little level…nice.

    Another thing I did not know, BKL rings are manufactured by AirForce Airguns in Texas. Good stuff.
    I learned a few things from this video and thought that others might like it well.

    https://youtu.be/5bRTFNYBIkw

    Geo


    • Geo,

      Got them on my M-rod. Love them. On a good dove tail,… you have to spread them to even get them on. That is grip right up front (before) you even tighten them. For a standard ring upgrade,… they are the go-to.

      Also,… for those shimming,… the closer the rings are together,.. the more effect the shimming will have. Me? I like to center the rings on the fore and aft tubes. It looks better.

      Chris


      • I think the BKL adjustable mount is a much better option than shimming.
        I had to use the spreader holes to get the BKL offset mounts on my Urban too.
        I think you would like the video though…


        • Geo,

          (Got it saved for future review). I was not aware they made individual rings that were adjustable. 1 piece riser/adapters maybe. I went with the Sportsmatch adjustable rings for the Red Wolf so I would not have to shim and wanted to control windage shift if needed. I only shim the bottom rear. Never any side to side shimming.

          Thank you. You are real good at finding good stuff. 🙂

          Chris


          • Chris,

            You are correct, the adjustable rings are NOT individual rings. It is a one piece adjustable mount with the rear ring being able to adjust upward. It is the very same mount B.B. installed on my Diana 34 last summer when he reviewed it for me. The BKL offset rings I bought for my Urban are self centering and I did have to spread them slightly to get them onto the rail.

            Those Sportsmatch adjustable rings may be a step up, and nice that they can be adjusted for windage as well. I would only be using the best of everything on a Red Wolf like yours too.

            Wouldn’t it be nice if all rings were designed with just a little rise on the rear ring? It seems that it would be better to to dial the scope elevation down a bit rather than always upward.


      • Chris
        What Geo just said explains what we was talking about with that AirForce scope riser I put on my Condor SS. AirForce makes the mounts. And that’s why it is that self centering design.



Leave a Reply