Hammerli trainer: Part 5

by Tom Gaylord
Writing as B.B. Pelletier

A history of airguns

Part 1
Part 2
Part 3
Part 4

This report covers:

  • Thanks to August
  • A BB gun
  • Gravity feed
  • Clean targets
  • Sight-in
  • Air Venturi Steel BBs
  • Hornady Black Diamond BBs
  • H&N Smart Shot lead BBs
  • Avanti Precision Ground Shot
  • Summary

Today we look at the accuracy of the Hammerli trainer that was made in the 1950s for the Swiss K31 Schmidt Rubin military rifle. It has taken some time to arrive at this point, because the trainer wasn’t working when I bought it. I could tell something was jammed in the barrel, and after disassembly it proved to be several steel BBs and some chunks of lead. But during the disassembly process I lost two ball bearings that play a vital role in the trainer’s operation.

Thanks to August

You can read Parts 3 and 4 to learn what happened to me when I disassembled the trainer. It boiled down to loosing those two ball bearings, then finding one of them and wondering whether there was another one I couldn’t find. Reader August saved the day by locating a web page where someone talked about the assembly of the trainer and that was where I confirmed there are 2 bearings, not just 1.

Part 4 of this report describes the assembly procedure, which is something of a Chinese puzzle box. The two bearings actually form the sear of the trainer and have to be assembled correctly to work. It is an ingenious design that adds nothing to the crisp 2-pound trigger pull of the K31.

A BB gun

Since the trainer is essentially a BB gun, I decided to test it like one. That means BB-gun targets at 5 meters. I rested the rifle on the UTG Monopod rest, which you have learned from past reports is about as stable as a bag rest when done right. It’s certainly steady enough for this test. But it gave me one problem I wasn’t anticipating.

Gravity feed

The trainer feeds by gravity. If the muzzle is elevated slightly the BBs roll back and fall into the breech one at a time when the air tube on the piston uncovers the place in the breech into which one BB will fit. I forgot that when I was shooting off the monopod. The trainer cocks so easily that I left the rifle level and on target every time I cocked. Invariably the fifth BB failed to feed. But when I elevated the muzzle a bit it fed perfectly. You need to keep this in mind when using a gravity-feed airgun.

Clean targets

I wanted to show you how I set up the targets on the UTG Pellet/BB Trap, so the BBs will poke reasonably clean holes in the paper. First I tape the targets to a cardboard backer in the front of the trap, then I use wide shipping tape over the bullseye area on the target. [Note — the tape over the target doesn’t work. I explain that at the end of this report.]

cardboard backer
A sheet of fresh cardboard is slid into the front of the UTG BB trap. Targets will be taped tightly to this.

tape over bull
It’s hard to see, but there is a piece of wide tape over the bull on this target. [Note — this doesn’t work.]

Sight-in

Because the trainer comes out of the K31 easily, I believe the point of impact probably changes each time it’s installed. I had it zeroed a week ago but when I shot this time the BBs were hitting high. The good news is you adjust the rifle’s sights exactly as you would for firearm ammunition. The K31 sights adjust for both windage and elevation. Elevation is by raising and lowering the rear sight leaf, and windage is by sliding the front post from one side to the other.

K31 front sight
Looking down on the front sight we see that it goes left and right when slid in its channel, fore and aft. It’s staked to remain tight in the groove.

Air Venturi Steel BBs

First up were Air Venturi Steel BBs. Five of them went into 1.379-inches at 5 meters. That wasn’t what I expected. I was hoping for a group that’s closer to what the Daisy 499 can do.

K31 Air Venturi group
Five Air Venturi BBs went into 1.379-inches at 5 meters — 3 in the bull and 2 to the right. I expected better from this trainer.

Hornady Black Diamond BBs

Next I loaded 5 Hornady Black Diamond BBs into the magazine and gave them a go. Four of them went into 1.174-inches, which isn’t too bad, but the last shot (it was actually the second in the string) opened the group to 3.11-inches. Not very impressive.

K31 Hornady Black Diamond group
Five Hornady Black Diamond BBs made this 3.11-inch group at 5 meters. Four together and one at the bottom right.

Wow! This wasn’t going the way I expected. Maybe there is more to learn about this trainer. Of course it is true that the shotΒ size should be 0.175-inches, according to author W.H.B. Smith. I thought I had disproved that when I stuck an Avanti Precision Ground Shot in the barrel in Part 4, but we will see in a little bit what else that could have been.

H&N Smart Shot lead BBs

I tried H&N Smart Shot lead BBs next. I thought they would be the last BB I tested, but I changed my mind after seeing what they did. Five BBs went into a group measuring 0.979-inches between centers. While this is nowhere near what the Daisy 499 can do, it does show some potential for the trainer. I think I need to do a little more testing.

K31 Smart Shot group
This is more like it. Five Smart Shot lead BBs are in 0.979-inches. Not great, but certainly better.

Avanti Precision Ground Shot

In Part 4 I said I thought the Daisy Avanti Precision Ground Shot was too large for the bore of the trainer and I would not test it farther. Well, in this test I learned that the way I was holding the rifle (level, so gravity could not act on the balls in the magazine) was causing the problem. So I loaded some Avanti Shot and gave it a try.

Five Precision Ground Shot went into 2.03-inches at 5 meters. That’s the second-worst showing of the 4 BBs tested, and looking at the scattered shots I would see no reason to test this ammunition any farther.

K31 Avanti Precision Ground Shot group
Five Avanti precision Ground Shot landed in 2.03-inches at 5 meters. Nothing to see here. The test is over.

Summary

First, I have to observe that putting tape over the target face does not improve the BB hole. In fact it makes it smaller. Just tape the target to the cardboard backer tightly and leave the target face alone.

We spent a lot of time with this Hammerli trainer. Much of that was spent fixing it and learning how it works. It was a challenge, but now we know its secrets.

I don’t know if I will return to this airgun in the future, but I can tell you that I do intend keeping it. I just wonΒ Β a K31 rifle of my own on an auction site to house the trainer, so I can give Otho’s rifle back to him. What a great journey this has been!

80 thoughts on “Hammerli trainer: Part 5

  1. Vert nice report,,
    I have always loved the K31.
    I know you might not revisit it, but the smart shot group makes me wonder if other lead bb sized shot would fare as well or better.

    Could it have been designed with lead shot in mind?


  2. BB
    Congratulations on your K31.

    I bet Otho is glad too.
    πŸ˜‰

    And I’ll say it again. I do like this military trainer air gun action. I wonder if the soldiers that trained with the air gun insert had their very own for their K31 or if they had to share the insert from gun to gun. Or maybe they had a dozen or so K31’s that were designated guns with the trainer insert.

    Still cool idea of the air gun insert. And I still think the ball bearings was a good idea. Very minimal contact area for very little resistance.


  3. B.B.,

    It was great that you played around with trying to get cleaner holes for the bb’s. I have yet to find the “perfect” recipe to get a super clean hole with bb’s. Both Gunfun1 and I use duct tape, and now Gorilla tape, taped to the (back of the target paper) and works great (for pellets),…. and while not perfect,….. remains the best option for bb’s as well. Of course, a cardboard backer just as you did. The problem arises when getting 2 holes touching or very close. All types of tape, and I mean a bunch of types, will tear or split at some point with bb’s.

    The clear types of tape, which one would think would be good, as they are plastic,… will tear/shatter. The duct tapes will tear along the fiber/string lines as well, but is better than any clear, again,… with bb’s. I have not tried bb’s fired in the 700 fps range yet though.

    Pellets hit harder and faster and work very good with the duct tape on the back of the target paper. I can overlap 4 shots and see the outline of each pellet, (with zero paper tear). You use official target paper and I use a high quality graph paper, so I can not comment on any difference that may make.

    One thing that you mentioned was that the holes got smaller with the clear tape. That struck me odd at first, but then I realized that you were probably looking at it from a (scoring) stand point, where a smaller hole could mean the difference between a 9 or a 10. For going for center to center measurements, I would think that a small, crisp hole would be a good thing.

    At any rate, thanks for trying something to improve the bb holes. Have a great day,…… Chris


    • Chris,

      Yes, I have the same problems everyone does getting BBs to show up clearly. Target paper is good because it has no grain orientation. It tears equally well in all directions. But BBs still don’t cut it cleanly.

      B.B.


    • Chris USA
      I do it a little different than you and similar to how BB does.

      Simplified here but this is part of my pellet stop. I have about a 1″ thick part of a phone book Gorilla taped very firmly to 2Γ—4’s. It will accept a peice of 11Γ—8.5 “white copy paper.

      What I do is draw little red dots on the copy paper or put those colored binder stickers on the paper that you told me about. Then I take 4 peices of masking tape on each of the straight edge of the copy paper. Then tape it on the Gorilla tape thats holding the phone book to the 2×4’s. So the sticky side of the Gorilla tape is toward the phone book. The smooth outer surface is facing the back of my copy paper target.

      So what I do different than you is the Gorilla tape is (not) sticking to the back of my target paper. But what I do similar to BB is I pull the masking tape tight on my copy paper when I attach it to the (non-sticky side) of the Gorilla tape.

      And I do get very clean holes. And matter of fact I just did some shots at it with the 760 at 10 pumps and some steel bb’s to verify again. Yep clean distinct holes. No tares.

      Oh and I mentioned before that my stop will work for standard velocity long rifle .22 rimfire ammo. It’s because I have a 1/8″ steel 11Γ—8.5” steel plate behind the 2Γ—4’s. And yes the Gorilla tape holds the steel plate to the 2Γ—4’s.


      • GF1,

        Well,…. there you go,…..or should I say,….. “there you go B.B.”. Something to try at least. Me, I am not too concerned with bb groups or scoring, but I am sure there is those out there that are.

        And in case your wondering, it was slow at work, so I took some paid time off. πŸ™‚


        • Chris USA
          I’m off today too. Just got through cutting the grass for the second week in a row. It’s starting to grow like I don’t know what already.

          And getting ready to put a cold air intake with a K&N cone filter on the turbo car I just got. Yep already modding it and only drove it for 4 days now. And you only thought it was only air guns. πŸ™‚

          Then going to do the setscrew mod on that Disco trigger assembly I have on that 1377 gun I converted to a pump version of a Discovery.

          So got a few things going today.

          What you doing on your day off?


          • GF1,

            I just posted a nice response and it vaporized. πŸ™

            Abbreviated version,…… grass is fine, 42 degrees, indoor shooting,….. and if I see many more squirrels,…… it will be full on WAR! Drop a window and have a go at ’em. Had ’em chew and cut car wires in the past.


            • Chris USA
              I can relate to the sqerrials.

              Some years back I had pulled the muscle car out of the garage I had at the time so I could do some spring cleaning in there. Came time to pull it back in and when I started it herd some strange bumping sound coming from under the hood. Well out comes a sqerrial scooting butt across the yard.

              Looked under the hood and it chewed through the wires for the heater blower motor. But I think it learned its lesson. Because there was fur everywhere under the hood. I had one of those flex cooling fans on the water pump. I think it got a taste of it.

              But yep those sqerrials will destroy stuff. See what happens when they get in your attic of your house. They will chew wires and whatever else they can get hold of.


            • Update on the Discovery trigger mod that Buldawg was talking about the other day when he was talking to BB about the two long screws for the Hatsan break barrel to get a better trigger out of the Hatsan.

              So here’s the out come on the Discovery trigger. I put two 5-40Γ—1/2″ long screws in the holes in the back of the trigger housing like Buldawg said. He thought originally that the screws were there from the factory. And my older trigger housing had the bosses there already. And the holes were all the way through. They had a plastic flashing over the holes from the molding process I guess. So it was real easy to screw the screws right in. They cut there own threads in the plastic. Which is pretty common when doing threads in plastic.

              I lightened the spring for the sear that also holds the safety button from falling out. And then lightened the spring behind the trigger blade.

              Adjusted the top screw for trigger travel and the bottom screw for trigger stop.

              100% better trigger now. Very light smooth pull till you hit a distinct stop which I have set at about half of the triggers full travel. Then a very slight pressure and the shot goes off and the trigger blade stops right there the way I have the bottom screw adjusted.

              All I can say is. Crosman if your listening. Add those two screws to the Discovery trigger housing. It’s a big difference.


              • GF1,

                Way to go!!!! Another success. See,…. it does “pay to play”, for those that have their doubts.

                Disclaimer,…… do your homework first.

                I will say that from a newbie standpoint,…. the more you do,…. the easier it gets. Before long,….it’s like,….”yup,…been there, seen/done that”.


                • Chris USA
                  Yep for sure happy with it.

                  And yep on the disclaimer part. And seriously. If you don’t understand what your doing. Then you probably shouldn’t. Heck things can go wrong even when you do know what your doing. It’s just the way it is.


                  • GF1,

                    Been doing “homework” all day. The list is getting shorter. LP Comp. looks to be a California Air Tools for 169. I E-mailed Dave at R-Arms again. No phone # on his site. πŸ™

                    What would you suggest for pellets? I figure I will do a can just on set up and initial shooting. Pretty much down to a scope and mounts.


                    • Chris USA
                      I guess you mean pellets for a .25 Marauder.

                      Well for the longest time I shot the 31.02 grain H&N Barracudas.
                      /s/p/H_N_Baracuda_25_Cal_30_86_Grains_Round_Nose_150ct/19

                      But I tryed the JSB King 33.95 a little while back.
                      https://www.pyramydair.com/s/p/JSB_Diabolo_Exact_King_25_Cal_33_95_Grains_Domed_300ct/1269

                      And not the mkll though. They are a little shorter. They made those after people said they were having problems with the regular 33.95’s being to long for magazines.

                      So now I shoot the regular JSB 33.95’s that I gave the link to above. In my modded Mrod they are better than the Barracudas at all distances.

                      An example is at 50 yards all pellets are always touching with the JSB’s. Even 10 shot groups. With the Barracudas some pellets would not be touching the main group. The would be close. But not touching.

                      So with my long distance shooting I want the pellet that’s gong to do the best.

                      The farther out you go. The more the group size increases. And the difference in performance from the JSB’s to the Barracudas is enough for those few pellets to not be part of the main group at 50 yards would be a definite miss out at a 100 yards or more.

                      So the JSB’s for me now.


  4. BB,

    Thanks for the blog on this. It has been most interesting.

    I am with 45Bravo. I personally would have to keep trying different size shot until I found “the one”. Of course, that could take some time and there are hundreds and thousands and millions of other air rifles and pistols to shoot and write about and we are a ravenous and demanding lot are we not? It’s a tough job, but somebody’s got to do it.

    πŸ˜‰


  5. BB– Was the bore damaged by the stuck shot, and its removal? Can you slug the barrel to see if there is an enlargement of the bore where the shot obstructed the bore ? Ed


    • Ed,

      The force I used to remove the BBs wasn’t enough to damage the barrel. It probably didn’t even leave a scratch. Slugging the bore sounds like a good suggestion, but I’ll have to find a lead ball to do it with.

      B.B.



  6. I was impressed with the method for adjusting the front sight blade. It looked to me to be the answer for making small lateral adjustments, which could easily be corrected or even returned to the original setting. A relatively gross adjustment would result in only a small change in blade movement, something other methods lack. No sliding in dovetails, no bending, no gears.

    Les




      • That’s the way the Swiss work.

        The machines at the machine shop I work at are Swiss made. Hydromat rotary transfer machines is what their called to be exact. Very precise machines and maybe even over engineered sometimes.


        • GF1,

          l found a nice AR style adj. butt and riser at Wally’s on clearance. (Mission First Tactical) BUS version with the BACP cheek riser. The issue is that is commercial, not mil spec. The RAI/R Arms M-rod (adapters) will fit both, but the gas tube appears to be mil. spec., at least with the “kits”. They do not sell just the gas tube.

          So will a mill spec. gas tube work with a commercial stock? The diff. were noted on the rear of the package, but I failed to write them down. I do not to end up with “slop” in the stock.



            • GF1,

              They (are) different on the OD by a few thousands of an inch. Tolerances I suspect would come into play as well. First inclination is to stay matched. The set at Wally’s is as good as I have seen. I may just have to get a comm. tube. Maybe someone else will know. If not, I plan to give R-Arms a call.

              Thanks, Chris


              • Chris USA
                A few thousands as in .002″ you will never know the difference. But if your talking .005 -.010″ then you might feel some slop.

                And probably you should ask Dave. He knows what his stuff is held at tolerance wise. He told me about it a long while back and I don’t remember now what he said. So that would probably be your best bet would be contact him.




                • GF1,

                  Thanks for the above info.. Notes made. Will those do ok in a stock M-rod or a stock M-rod that can be adjusted with the factory adjustments? We’ll get into the modding later on,… once I get everything and shoot it a bit.


                  • Chris USA
                    The 33.95 JSB’s shoot with just about the same trajectory as the Barracudas in my Mrod. And by that I mean once I start getting out at a 100 yards and past I need about another 1/4 mildot out of the heavier JSB’s.

                    And as far as the Barracudas go I shot them in 3 of my .25 caliber Mrods I had. And they done well in out of the box factory tunes. I tryed the lighter 25 grain JSB’s in all of the .25 Mrods I had and they just don’t seem to do as good as the Barracudas.

                    And the heavier JSB 33.95’s came out after I already had the Mrod I have now modded. So I didn’t get to try them in a stock gun. They could work. And you know me I like heavier pellets in my guns. So the 33.95 JSB’s could work in a stock Mrod.


                    • GF1,

                      Well, 25~33 seems to be the avg. range of weights, so that is why I asked. Notes made of the other 2 you mentioned. By the way, the Husky’s did not fair well on reviews from Home Depot. 2 star avg. at best. They must have cheapened up since you got yours. I was looking in the 150~225 range, which there is many that will fit the bill in that range. Reading the reviews seems to be the best research, but it is very time consuming.



                  • Chris USA
                    I don’t think that Husky makes the one like I have anymore. Mine is the dual tank model and its red. I believe I posted a link nkof what mine looks like in the past. I think their new model is black and they changed the gauge location.

                    And just curious what did they say in the reviews you read about them. Was the reviews in reference to air tools and such. If so that could be why a bad review. That size compressor is not big enough for most air tools with the exception of air nailers.

                    And remember when you are looking for a compressor to supply the first stage air for a HPA pump it has to be a oil less design.

                    Are those higher dollar compressors you mention oil less?


                    • GF1,

                      Yep on the oil less. On the Husky’s, it was belt breakage, thermal load shut down, noise and regulators breaking. It was all on the comp. and no tools. I am not looking for a combo, so I focused on that. 60 is the quiet end and 75-80 DBA seems to be norm.,….. if you can find that info.. I will be using it indoors. The California brand wins hands down on all categories. Reviews only go back around 1 year, so they must be relatively new. They do offer quite the line up all the way to 3000$ units as well as high end stuff that has really good dryers built right in.


                  • Chris USA
                    If you can post details about the California pump. You know a part number and such. Like you did with that dot sight that you were looking at from Wally world.

                    I would like to check out the model your looking at.


                    • GF1,

                      Go to the Home Depot site and narrow the brand down to the California Air Tool brand. They appear to be out, but had the most reviews. Lowes can get them, but had 0 reviews. At any rate, the 2 I was looking at was 5510SE and the 6310, but it appears the first one replaced the second one. Either way, they both looked good.

                      Move to bottom,…. up here is getting a bit scrambled.


  7. If you just let a BB roll down the barrel is it loose or tight? I remember reading that on the 499 the BB’s took a while to roll down. Also, did you check velocity again after the tear down and rebuild?
    Might be difficult to find out what brand / size of BB’s that was made to be used with these. But, with all of the modern day offerings a good fit should be attainable.

    Silver Eagle



  8. Girlfriend search took a BIG turn for the worse! Finally tried a online dating site under the pretense it was a free trial membership and a week later I’m broke!


  9. Deactivated my card and shredded it so there’s a new one in the mail, just filed a police report so I can get ALL MY money back and about to put it all behind me.



    • Reb,

      Sorry to hear all that. At least here, if someone takes your money, you will get what you bought. A good bunch.

      Last I remember you were getting your “supply” together for the big show. How are the “projects” coming along?


      • Still got stuff torn down all over the house and not making much progress without the parts necessary to make them fully functional. The last time I had the Powermaster66 together it was a sweet shooter but the air was blowing the bolt open enough to only be about 50% efficient, that’s why it’s back down now.


  10. Most of my guns are in pawn so I haven’t been doing much shooting lately but right now I’m putting my efforts into correcting as much of this mess as possible. I’m pulling as much information as possible outta these Ticks & Leeches as I can before I finalize the police report to get them red flagged or arrested and already reported the fraud to my CC company and will be reimbursed for ALL that money. AND anything more will be me getting one up on them! I truly believe in karma! Only sometimes it is a little slow to act on its own and needs a little push to get started. Setting up a little sting operation of my own! Still got one texting from the Philippines trying to get money for a return ticket and with no ID because “she got robbed” so I’ll have to send it to her cousin instead? That name and address will be in the police report as well!


    • Reb,

      Well, it sounds as if it will all work out. Now,…. get back to those airguns as soon as possible, so that you have something to take to the show and sell or trade.


      • I’ll be there! YOU coming too? Awesome! I’ll have stuff ready because I already do but it’s gonna be tough letting them go because I’m fixing them to MY standards instead of just slapping them together. Some will take years to find or fabricate parts for and I’m not gonna rush because they will be right when I get done!







                • GF1,

                  Yea, just hope I hear beck from R-Arms/Dave. With the set up I am looking to do, it is a bit of a mix and match and not something he offers on a std. basis. I never did hear back the last time. That don’t sit well with me,… with me willing to spend that coin at his doorstep.


                  • Chris USA
                    He’s had some health issues that he asked me not to mention. So I maybe said more just now than I should of even.

                    I have his phone number. I talked to him about a week or so ago. I’ll text you his number in a minute. Then you can take it from there.


                    • GF1,

                      All good,.. it looked like a small operation from the site, sort of Mom and Pop, which I am cool with! Products look very high quality. I will call after work tomorrow. It’s the small guys that get the big stuff going,…. nothing to lose but some time and effort.

                      Hopefully all is well. It looks as if he originated the Teryx line and passed it off.

                      Thanks, Chris

                      I look forward to speaking with him, or at least get a reply back on e-mail.


                  • Chris USA
                    He usually picks right up. If he misses your call he will get back to you.

                    And that’s his second website. He had problems with the first and has somebody laying this one out for him. And I don’t quote me on this. But I believe had some issues getting this one going. I don’t know all the ins and outs about that stuff. But at least he has a website. I hate to think what would happen if I tryed to get a site setup.

                    But let me know how it goes. Oh and don’t give his phone number out unless he says you know.


                    • GF1,

                      Of course on the #. I see you getting into the same sort of set up in the future. The daughters would have you set up in no time. πŸ˜‰ That is of course,.. if you don’t go to work for P.A. in the near future……. don’t I remember something about a “resume” a short while back? You would turn that place on it’s head! πŸ™‚


                  • Chris USA
                    My plates pretty full right now. So don’t think I could keep up with extra work with PA. But that sure would be a awsum job I bet.

                    And they would get tired of me real quick I think. I tend to be a little to persistent you know.
                    πŸ™‚


  11. It was coming down this morning! We probably got about 3/4″ in a couple hours! The roads were flooded and still have ponding to dodge. Looks like another boring weekend alone πŸ™



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