Johnson Indoor Target Gun: Part 3

by Tom Gaylord
Writing as B.B. Pelletier

Johnson Indoor Target Gun
The Johnson Indoor Target Gun is a catapult BB gun that was made in the late 1940s for youth target practice.

Part 1
Part 2

A history of airguns

This report covers:

  • What kind of rubber?
  • Remove the old rubber
  • Measure the old rubber
  • Loops on each end
  • Install the new rubber
  • Ready!
  • Daisy BBs
  • Problems!
  • Got it going
  • Baseline
  • Shortened the rubber
  • Second Daisy test
  • Dust Devils
  • Two lessons
  • Shortened the rubber again
  • Higher velocity
  • Shortened the rubber another time
  • Last test
  • Summary

Today I install a new rubber band in the Johnson and if all goes well, we will see what velocity it gives. In case you forgot, when I got this gun the rubber was broken.

Rubber
This is how I got the gun.

What kind of rubber?

I have been shooting my other Johnson Indoor Target Gun for years, so I had 10 feet of 3/16” amber surgical tubing on hand for repairs. I will start with that.

rubber bag
I had this surgical rubber tubing from my other Johnson.

Remove the old rubber

Step one was to remove the old rubber from the gun. It might look easy, but wherever that rubber was in contact with the steel in the gun it had bonded. It took me 15 minutes to get all the little pieces out.

old rubber
The old rubber tubing was both brittle and gummy and stuck to the steel parts of the gun.

Measure the old rubber

Since I had it I measured the old rubber. The big piece was 8 inches long and I estimated there were another two inches among all the pieces. So — 10 inches overall. But what if the rubber is missing altogether?

Well, since you are reading this — 10 inches. But here is the deal. This is not rocket science (where IS our Rocket Jane?), so you experiment until you find what works. Heck — I don’t know that 10 inches will work yet.

Loops on each end

The next step is to make a loop on both ends that will fit over the steel hooks in the gun. They used fine string or thread for this years ago, but I found that small cable ties work well.

cable tie loop
Make a loop like this on each end of the new rubber. Make the loop small because this stuff stretches.

Install the new rubber

All you have to do now is install the new rubber where the old one came out. It took about 10 seconds. I attached both loops to the hooks then stretched the rubber over the carrier as shown below.

rubber installed
Install the new rubber where the old one was.

Ready!

The gun is ready to shoot. For today’s first test I counted each BB that I loaded into the magazine tube that’s on the top cover.

Remember what I said about how to cock this gun (and stretch the rubber)? Use a ramrod to push the launcher back, after pushing it forward to catch the rubber. This preserves the plastic launcher and the two thin steel hooks that are used to pull it back during cocking and loading. See this in Part 1. Both things will break in time if you don’t do this. Let’s go!

Daisy BBs

First to be tested were Daisy Premium BBs.

Problems!

Oh, my gosh! The launcher wouldn’t catch the rubber when pushed forward and then, when I figured out how to make that work, I could not get the launcher caught by the sear!

I spent some time opening and closing the top cover to discover what could be wrong. In the end, though, I think it was mostly due to a catapult gun that was made in 1947 being used for the first time 71 years later! Hey — this gun is as old as I am! No wonder it doesn’t want to work.

Got it going

I played and played with it, solving one thing after another. Nothing had to be fixed — I just had to do a lot of funny things like push the launcher forward repeated time to get the rubber tubing to pop into its groove, and then I had to pull the trigger several times before ramming the launcher back to the sear. Once I figured it out the gun shot well almost every time.

Baseline

Every time I have tested a Johnson I have gotten velocity averages with steel BBs of 100-101 f.p.s. Guess what I got this time? 101 f.p.s. I got that shot after shot after shot. The low was 99 f.p.s. and the high was 101 f.p.s. I remembered how very stable catapult guns are

But this time I had played with the mechanism like never before and I now knew that I was the problem all along. I must have always cut the rubber tubing about 10 inches in the past, because I always got the same velocity. Time to do something different.

Shortened the rubber

I removed the rubber and snipped off about an inch from one end. Then I made a new loop at that end and reinstalled it.

Voila — the launcher is now catching the rubber easier when I push it forward. It isn’t 100 percent and I still have to fiddle a little, but it’s much more reliable. The trigger still has to be pulled several times to catch the launcher when it is rammed back.

Second Daisy test

This time Daisy BBs averaged 116 f.p.s. That is the fastest I have ever seen a Johnson shoot. But like I said — I was the reason for that all along. Now I knew that a shorter rubber would increase the velocity — time to test some other BBs.

Dust Devils

Next up were Dust Devils. Now Dust Devils are considerably lighter than Daisy BBs, so they should go faster — right?

Nope. Dust Devils averaged 116 f.p.s. Oh, one of them did go 117 f.p.s. and one went 115 f.p.s., but what the hey?

Two lessons

I learned two things from this test. First, I don’t need to shoot 10 shots and then average the string with the Johnson. One shot is all it takes. This gun is incredibly stable, as far as velocity goes.

The second thing is I don’t need to test a range of different BBs. If Daisy BBs go a certain speed, all other steel BBs are going to go the same speed. See — an old dog can learn new tricks!

Shortened the rubber again

I removed the rubber and snipped off another inch. Then I made a new loop and installed the rubber in the gun. Since there were still some Dust Devils in the magazine I went with them.

Higher velocity

This new setup gave a velocity of 129 f.p.s. I shot it a second time and it was another 129.

Shortened the rubber another time

I snipped on another inch and made a new loop but now the rubber looks really short. So I laid it next to a ruler and photographed it. I said I have been snipping off an inch each time, but it looks like it has been more than that.

short rubber
The rubber has gotten really short!

Last test

I installed the new shorter rubber and fired the gun one last time. The velocity was 116 f.p.s. because the rubber broke upon firing. I did see some abrasions on the left side of the rubber this time when I stretched it to fit the gun.

short rubber installed
The new short rubber is on the hooks but hasn’t been pulled back over the rear yet. As you can see — it’s really short! Notice the left side of the rubber. I think there are some small abrasions there.

short rubber broken
Just one shot and the rubber broke. It was probably too short, though those abrasions may have caused this.

Summary

What I have learned is with this surgical tubing I should start with about 7 inches and go from there. Not only is that good for me to know, now everybody who puts one of these Johnsons back in service knows what to use and how much, as well.

I also learned that the velocity is what it is. It doesn’t vary. Shoot one BB and that’s where your gun is shooting.

Finally I learned that the brand of BB probably doesn’t matter that much. Of course I haven’t tested any lead BBs yet, but I think this holds for all steel BBs.

I’m not done with the velocity test. Some readers who are into catapults suggested a different type of rubber and I bought some. So we are still experimenting.

87 thoughts on “Johnson Indoor Target Gun: Part 3


  1. B.B.,

    Your previous experiments and comments have shown there is a limit to the velocity that can be achieved. Adding more bands or increasing the tension allows a heavier ammunition to be used with the same velocity.

    Siraniko


  2. BB: This is a fun gun and I am enjoying your review of it. I can possibly add a bit of information regarding the “power source”. I purchased 2 of these guns with boxes from a Johnson rifle collector and the one I kept has a plastic zip-lock labeled “original” with 1 complete rubber and pieces of one more. The tubing (based on my measurements) is 1/8″ I.D. (a 1/8 drill fits in it) with 1/32″ wall which is a standard size for surgical tubing. Both ends were secured by a metal band crimp which has the feel of a factory process. This makes me think that they might have come with the gun when new but all I can say for sure is the person who labeled it knew how to spell “original”. The distance between the metal bands is 10″ and I used this as my standard length when I made replacements.
    The crossed rubber in the gun happened during the show as I opened the gun and closed it back several times while showing people how it worked.



      • B.B.
        Most people think in whole numbers (most commonly even ones) when starting to lay out a design whether it is for a gun or a chicken coop. Most of us are wired that way so it isn’t too surprising that the rubber would be an even number and, if you allowed 1 inch for he loop on each end, you would start with a 1 foot piece of rubber. On the other hand I could be totally wrong! I am looking forward to your speed trials, just use a heavy backstop like 2 pieces of tissue.
        One thing I noticed is the difference in material from the old tubing to the newer. The older tube is a darker color and did not get “sticky”.


  3. BB,

    I sure would enjoy playing with a Hodges. I don’t know if they still make them but it may be possible to convert a band powered spear gun into a pretty awesome catapult gun.



    • RR,

      The frame and trigger mechanism of a speargun could work but the band would have to change to something with a faster recovery rate that was suited for a light projectile. For a speargun I imagine that the spear is fairly heavy and the band would have to be more powerful (which would make it slower) to handle the mass.

      The catapult gun design that I am playing around with would be a slotted-tube style.

      Hank




          • Hey Hank,

            Just an idea hair rain idea! Steel BBS and magnet; how do you think a cylinder of rare earth magnet powered by elastics surrounding a barrel made of Delrin would do? It would be self-lubricating and require no slot(s) carriage or carriageway? Could have a taploader or some other loading system.

            shootski


            • Shootski,

              I have made quite a few projects with the rare earth magnets and they are pretty awesome – the 1 inch diameter, 1/8 inch thick ones that I have used as clamps have a 30 pound pull!!

              Interesting idea there, coupling the the launcher to the elastic with magnets. Could see two possible problems with that, it might make the launcher too heavy and a ferrous projectile may have difficulty escaping the magnetic field.

              Hank


              • Hank,

                I think a magnet of opposite pole orientation at the end of the barrel could be used to negate the field. This is just a thought exercise for me based on physics class lessons. Considering how small the mass of a BB is I don’t think it would take a very large magnet or magnet array. I’m going to continue thinking about the concept for a time. It may just prove to be a dead end but the process of building the case for or against it working will be fun!

                shootski



                • Shootski,

                  I have played with strong magnets on the 499 as the barrel is accessible inside the outer shroud. The idea,.. at the time, was to try and “induce spin” on a steel bb. I also tried it with a solid barrel. It did seem to improve things. At the least, it was no worse as I recall.

                  I tried spacing the magnets,.. placing them all fore and all aft,.. and even spiraling them. The downside was the bb had to be ram rodded (with minimal effort) down the barrel (as opposed to dropped in) due to the magnetic influences.

                  Fun stuff and fun to play with. If not mistaken,.. the Red Wolf I have has a magneto coil that draws back the striker to a pre-set amount. A coil gun, so to speak. That is some interesting use of magnets (fields) if you ask me.

                  If I was going to make something home made,… something along that line would be of interest.

                  Chris



                    • GF1,

                      I still think that magnets (at target) could “guide” a bb to a “true” hole in hole bull.
                      Kind of like a “funnel”. The bb would have no where to go except to the same point over and over.

                      It is above my head,… but it should be interesting to hear some smarter folks thoughts.

                      As I looked up the rail gun,.. I ran across other videos. Even ones that made homemade, smaller versions. I know we have talked about rail guns here in the past.

                      Chris


                  • Chris
                    I would say yes if the magnet was strong enough and within a given distance the bb might be able to be pulled to that spot.

                    Or vise versa. Maybe a magnet of a given size could get launched at a target of metal at a location.


                    • GF1,

                      I was thinking more along the way magnets can oppose each other. Put them in a ring, all opposing. Then, then the bb would find the center of that field, in theory. The bb would not touch any magnets. I have seen some desktop toys/gadgets where something appears to levitate, from what I assume is through the use of magnets

                      Chris




                  • Chris USA, et. al.,

                    I was just trying to keep it a band powered Johnson like gun!
                    The magnet was just a way to get rid of the bb carriage and maybe have a real smoothbore barrel.
                    As soon as you all saw MAGNET you just leaped in with both feet…rail guns don’t even meet BB’s wide definition for this blog….
                    Also!
                    I think a rail gun would require way to big of a battery pack or an awfully long and heavy extension cord ;^)
                    You all are always complaining about heavy guns and expensive power sources….
                    Maybe we could add a brushless hand generator to sweeten the railgun package!

                    All in fun!

                    shootski


                    • Shootski,

                      🙂 Yea,… isn’t it funny what a little bit of something get’s us excited around here? (note: exhibit A at page top) Making a Johnson band gun (or) a rail gun,.. it is all about the fun, failures and successes in making it.

                      You are right,.. the one I saw in on a YouTube video did have a large bank of what I assume were capacitors, or maybe batteries. About 12″ wide, 12″ high and maybe 3′ long. It was a bench dedicated set-up to be sure.

                      I did find the square barrel with the peel away carrier for the projectile interesting.

                      All in fun, as you say.

                      Chris



  4. A bit off subject.

    I was reading another airgun blog just now and it seems that Hatsan has come out with the Speedfire, their version of the Gamo Swarm. From studying the pictures on their site I am not too certain I like their solution. I know I do not like the glowy thingy sights. We will just have to wait and see how it does, I guess.


  5. BB
    I like the idea of the plastic zip ties. Simple but effective. For some reason I seem to use them alot for different things.

    And amazingly consistent. Can’t wait to see how accurate it is. And if it’s hard to aim or if it’s hold sensitive.

    What I’m wondering about does the gun bump forward when the slide stops. Is it abrubt or gentle?


  6. B.B.,
    I think the reason for a consistant velocity with any bb is because it doesn’t change the weight of what the band is moving. A 5 grain or 6 grain bb on a 100 grain cairage isn’t any real weight change.
    Gerald


  7. Off Topic:

    B.B. — or anyone,

    One of those “other dealers” has the Walther Parrus, with wood stock, on sale today for $99.95 — but it’s the .177 version. I own the Terrus in .177, and that’s a good caliber for that rifle. For $100 I would add a Parrus to my collection, but it seems to me that the Parrus is too powerful for .177. What are your thoughts?

    Jim



    • Jim,

      Don’t have either of those rifles but $100 seems to be a good deal for a Walther.

      I have a .177 Walther Dominator 1250 PCP which shoots very hot. Found that going to the JSB Monster pellets worked well.

      If you like that type of rifle and it is such a good deal it would be worth while to pick one up and try some of the heavier pellets. You can always sell it.

      Cheers,
      Hank


      • Thanks Hank. I have a couple of Walther air guns, and am very happy with them. It’s hard to pass this up at $100…..just don’t know if I’d want to hassle with selling it if I didn’t like it.

        Jim


        • Jim,

          With all the really nice airguns in the market these days it is very hard for me not to buy them “just because”.

          Usually, I purchase to fill a specific application or to upgrade to a better rifle (fishing rod, camera, tool… whatever). I say “usually” because I am a sucker for “just because” 🙂

          Good luck Jim!

          Hank


          • Hank,

            Without saying a whole lot,….. I will say that I (can) relate to your comment. 🙂

            Before I buy something,…. I have usually talked myself (OUT) of buying it 10 times prior, if,… that gives you any idea? 😉 LOL! What can I say?,…. I am a hard sell.

            Chris

            ( One single exception,… the Red Wolf. I went into “full melt down” mode on that one. 0% regrets there. )


    • I bought a Parrus in 22, and find it to be a super picky rifle. I have tried a pile of different brand/weight pellets/holds, with little success. I have read tests that showed the rifle to be accurate and tried the pellets recommended, again little success. That said, I have a Terrus that is a tackdriver with JSB 15.89. I’m not sure I would venture even $99 on a parrus, in either 22/177. Just my two cents…


  8. B.B.,

    With velocities just slightly over 100 fps, I wonder how much of the famed accuracy of the Johnson is due to a “tracer effect.” Before I packed it up (finally) for shipping this weekend, I took my sick Diana 27 out back and shot it some. The sight had shifted far off, but at .22 caliber and shooting around 350 fps., I could see where they were going and simply adjusted my point-of-aim accordingly.

    Also, I am curious if Richard Middleton still reads the blog and has any thoughts on this one.

    Michael


  9. B.B.,
    I’ll be curious to see what the other type of rubber is, as well as how well it works in this gun.
    With all the advancements in materials since the days when this gun was originally made
    there’s got to be something out there that will give a decent amount of shots before it gives out.
    Is there any way to polish the parts of the carrier that come in contact with the bands
    in order to prevent abrasion in that area?
    All in all, it’s an interesting old gun.
    take care & God bless,
    dave


  10. B.B.,

    The abrasions on the tubbing make me think a search for a compatible lubricant for the rubber chanel might be in order. Diver’s silicon grease or other silicon gassed lubricant might work to reduce friction/heat damage to the elastic(s). Also a MELT on any sharp edges would be a functional fix…of course this is a collectible so probably not in the cards.

    shootski



  11. “slingshot rifles” are rather common in China, and available on pages such as AliExpress. Typically they consist of a slidable front part (with a fork like a slingshot) and a rear trigger that holds pouch and ammunition. To load you slide back the fork, insert ammo in pouch, secure the pouch in the trigger and slide the fork to the front, where it stays in place by canting against the rail.


  12. B.B.,

    On the Chaser pistol, you mentioned the bottom, rear of the grip interfering with a more comfortable/correct hold. While pondering the rifle kit, I noted that the piece on the bottom of the grip must come off in order to install the stock. Removing that piece reduces the amount protruding. Since you are still going to do a 25 yard test with some sort of optic,… I thought that I would mention it.

    Chris



      • GF1,

        I was looking mainly at the reviews. Overall, not bad. The balance looks to be top heavy already,… even as light as it is. Cheek weld would seem non-existent. Therefore,.. some sort of electronic seemed to be the ticket to keep everything light and balanced. Of everything I have looked at,.. I like this one the best:

        https://www.pyramydair.com/s/a/CenterPoint_Optics_32mm_Open_Reflex_Sight_4_Red_Green_Reticles_1_MOA_Weaver_Mount/4470

        Oddly,.. very few other’s offer those options And, being a Weaver mount,… something like this:

        https://www.pyramydair.com/s/a/UTG_11mm_3_8_Dovetail_to_Weaver_Adapter_2pcs/4148

        At least those reticle choices give you some indication of hold over, if needed,… as opposed to just a plain dot. Would it show good in daylight? What puzzles me is, with all of the dot sights out there,… why do none have mil-dot/reference lines?

        And, do I really “need” something else? Then,.. on the other hand,.. it does look like fun and I would like to have a go at the trigger and bolt in a tear down….. 😉

        My gut tells me that I will end up with one in the end. By the way,… last I looked,.. the 11% sale is still up that ended at midnight, last night. Extend it or take it down I say. Maybe they will do a Cyber Monday sale?

        Chris


        • Chris
          The the 3/8 to Weaver adapters are good. I have uesd them on spring guns even.

          And they extended the 11% sale to 5 pm EST.

          And here’s the type of dot sights I use basically because it has 11 brightness adjustments. Some times you need that if it’s bright sunshine outside. It’s the type I use.
          https://www.pyramydair.com/s/a/Hatsan_1x30_Red_Dot_Sight_Fits_11mm_Dovetail/6662

          And if you stay within a given distance of let’s say 15-40 yards you probably won’t need hold overs and unders. Just aim center mass. And that would be a Starling size target at those distances. Dot sights are alot like aiming with open sights. But with out having to line up the front and back open sight. With the dot sight you just place on target and shoot. Oh and the flatter the trajectory that your gun shoots the better.


          • GF1,

            The .177 I was considering should be flatter shooting. Given the effective range, for say a squirrel,… the plain dot may work just fine. I do prefer the closed in tube format to the open reflex. If going for a fuzzy tail with one of these,.. I would keep it to 30 yards max. and maybe less. Basically, walk up to the tree that the target is in. I do have the scoped Maximus for squirrel, so this would just be a close up alternative. Still not sure I need anything else though,…. 😉

            Chris


            • Chris
              You always need another gun. 😉

              And yep the .177 should shoot flatter than the .22 version.

              And I basically had the same set up as the .177 Chaser rifle in the past. It was a 2240 with a steel breech and a .177 Discovery barrel. I could get Starlings and squirrel from 15-40 yards no problem with the JSB 10.34’s and the red dot sight and of course the 1399 Skelton stock.

              It’s a very nice setup if you stay in those distances. Almost hard to miss. I’m thinking the Diana Chaser rifle kit should do good to at those distances with a red dot.

              I almost got one with the sale they are having. Heck maybe they will have a good Cyber Monday sale. Maybe better than the 11% and free shipping over $150. You never know.


              • GF1,

                And we all call B.B. the “Great Enabler”!!!!,….. (“You always need another gun”) 😉 Another thing that bugs me is that they did not even seem to make an attempt at getting the ergonomics right on the grip. Even something (half-way) to the 2240 grip would have been a MASS improvement. My 2240 fits my hand very well.

                Chris



                • Chris,
                  I have the open reflex you mentioned and the mount adapters. one adapter is enough as using both would extend past the sight base. I have it on a modded 2240 and only shot it enough to sight it in. I picked it over the enclosed tube because it is smaller and lighter. Also it looks beter on a pistol.
                  Gerald


  13. Just spent a little trigger time with Lloyd’s Benjamin Rogue. After mounting and zeroing a scope, I started playing with three shot groups with 81 grain JSBs and 105 grain semi wad cutters at 25 yards. At the 100 grain low power setting the JSBs were tight cloverleafs but the semis were about 1 inch. At 100 grain medium the JSBs opened up a little and the semis tightened up some. At 100 grain high the JSBs opened to about 3/4 inch but the semis made a real tight cloverleaf.

    I think I am going to have to spend some time with this air rifle. It is starting to look interesting. 🙂



    • Chris,

      No, no, no. I just borrowed the Rogue from Lloyd to play with it for awhile. I had tried playing with it some a few years ago, but all I had at the time was a hand pump. Try shooting a .357 air rifle much when you are filling it like that. Not much fun. Now that I have a compressor and a tank I can blast away with it.


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