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Marksman model 70

Marksman model 70 breakbarrel air rifle: Part 11

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Marksman model 70
Marksman model 70 breakbarrel rifle.

Part 1
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
Part 9
Part 10

History of airguns

This report covers:

  • Update
  • How to proceed
  • Spacer
  • What did it do?
  • Cocking effort
  • What have we learned?
  • Summary

Today we do the last experiment of increasing the preload in the Marksman model 70 air rifle. The next report will be with a new mainspring.

Update

We have discovered that the most powerful state this rifle was in has been the state after I cut off the end portion of the mainspring that was bent. Then I removed almost as much mainspring again to bring the rifle down to very little preload.

After adding in a half-inch of preload by putting 8 washers inside the piston the power did increase, but not to its previous high point. Here is a reminder of where we were. All these shots were with RWS Hobby pellets.

10-shot average with extreme spread

Fac. Vel………..Cant spring cut……..More spring cut……..half-inch preload

715 (15 f.p.s.)….746 (12 f.p.s.)……….606 (22 f.p.s.)………689 (12 f.p.s.)

Cocking effort

28 lbs……………..22 lbs…………….………20 lbs……………..…….26 lbs.

Marksman 70 preload remaining
With most of the preload gone, this is where the threaded bushing is.

The 8 washers that I put in the rifle last time measured 0.456-inches in height. As you can see in the picture above, there was about 3/8-inches of preload on the mainspring at its shortest. The half-inch of the 8 stacked washers brought the spring out to what I am calling a half-inch of preload, but it’s clearly a little more that that.

Marksman 70 preload
With the half-inch of spacers, this is where the threaded bushing is.

How to proceed

Reader GunFun1 said I should use a lighter spacer to get more preload, because adding 8 more washers inside the piston would add weight that would change the performance characteristics. I had also thought about that and knew he was right. But my garage is not a machine shop. He offered to make a spacer for me, but I held off. I thought I could find something around here that would work. And I did.

Spacer

I found a plastic part from which I was able to make a spacer. It isn’t perfect, but I was able to get it to go over the piston rod. This is not a tuneup. This is an experiment to answer the question of what happens when you increase the preload.

Marksman model 70 spacer
The plastic spacer is so bright that you almost can’t see the hole through its center. I drilled it out to fit the spacer over the piston rod.

How much more preload is there with the spacer and two washers? It’s a little over one inch. Let’s see.

Marksman model 70 preload
I forgot to put the threaded bushing in this picture but it doesn’t take much of an imagination to see where it would be. Clearly more preload has been added.

What did it do?

This is the big question — the entire reason for this test. I would never leave an airgun set up this way. I just wanted to see what doubling the preload would do to the power.

The first three shots with Hobbys were 758, 740 and 728 f.p.s. Then I got a spread of 10 that went from a low of 731 to a high of 746 f.p.s. The average for the entire 13 shots was 740 f.p.s. The average for the last 10 shots was also 740 f.p.s. Only the spread of the 13 shots was higher (30 f.p.s.) than the spread for the last 10 shots (15 f.p.s.) I would say that 740 f.p.s. is a good average for the way the mainspring is preloaded.

Stock up on Air Gun Ammo

Cocking effort

The cocking effort is now 28 lbs. Let’s now look at what has happened over the course of all the work that has been done.

10-shot average with extreme spread

Fac. Vel………..Cant spring cut……..More spring cut……..half-inch preload…….one-inch preload

715 (15 f.p.s.)….746 (12 f.p.s.)……….606 (22 f.p.s.)………689 (12 f.p.s.)…………740 (15 f.p.s.)

Cocking effort

28 lbs…………..…..22 lbs……………………20 lbs…………………….26 lbs……………………….28 lbs.

What have we learned?

From this simple series of tests we have learned that having the mainspring alone do the job of preloading gives the most power — by a slight amount. The best power with the spring alone was 746 f.p.s. with Hobbys. 

The spring alone also gave us the lowest cocking effort, with the best power. The spring alone cocked with 22 lbs. of effort. The max preloaded spring (in this series of tests) cocked with 28 lbs. of effort — the same as the rifle from the factory.

What that tells me is that it’s best to use as much of the spring as you can, when trying for an optimum tune. You can get back most of the power when the spring is cut shorter by preloading, but at a cost of greater cocking effort. On the other hande, thin spacers can be added to nudge velocity up a bit. Keep them on the spring guide end and they don’t affect the weight of the piston.

This was just one simple test, and you see how much time and effort it took. Airgunsmiths learn these things the same way through their experience working on many similar airguns. They learn exactly what works best for certain models, which makes the time they spend to get what they want with one gun a lot less than the time you see here. But this kind of work is where they they got that experience.

Summary

I hope this series has been a learning experience for many of you. We still have things ahead of us with this Marksman model 70. The next step will be to find a good mainspring and tune this rifle nicely. We now have a chart of where it has been and what it is capable of, within reason, and I will use that as my guidline when I install the new spring.

Besides finding a good tune for the rifle I plan to install that other Perfekt trigger that came with the rifle. There is a whole story of why that trigger was in the box and I plan to share that with you in the future. Stay tuned.

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.
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100 thoughts on “Marksman model 70 breakbarrel air rifle: Part 11”

        • Yes, the angle when the rifle is broken open and the trigger sear is engaged. Cocking a Break Barrel with 28 lbs of force is much easier if you only need to cocking it 95 degrees vs. 150 degrees.
          It would be easy to make a cardboard protractor with several angles premarked and then you just lay the open, cocked rifle on the protractor and take a picture. Load and shoot…

          Thanks,

          -Yogi

          • Yogi,

            I find that as the angle becomes larger, the PERCEIVED force requirement becomes less.

            As for the reduced harmonics, a more solid structure with more mass will tend to absorb the vibration better, though I personally believe there are better ways to reduce the harmonics.

            I am not a big fan of long slots in the bottom of stocks either. To me, they create a weak point. You are anchoring a sproinger to the weakest points on the stock.

          • Got my protractor in hand…
            I believe that 28 lbs cocking force that only needs to be cocked 95-100 degrees is MUCH easier that 28 lbs cocking force that needs 120++ degrees to cock.
            Plus the underneath fore-end groove is shorter, leaving more wood to absorb some harmonics.
            That is my theory anyway….

            Short and sweet saves the day,

            Yogi

  4. Can we see an accuracy test with the extra preload? I’m rooting for this LNIB gun to duplicate it’s cloverleaf test group. Between the series on the HW30s, the HW50s, and this Marksman, I feel like you are spoiling us sproinger fans.

  5. BB,

    I wish to thank you for all of those times you have given us a peek behind the curtain. You have saved me so much grief over the years by doing these series and giving us a place to share with each other. By paying close attention to what is going on here I have managed to avoid an awful lot of pain and agony during my learning.

    I also wish to thank Pyramyd AIR for supporting this, most especially since most often this is not a direct infomercial for their products. They are not only giving to you a stipend to occasionally review their products, they allow you free reign to share us your wealth of knowledge and allow us to share ours.

    Many of “the others” are doing the “latest and greatest” reviews and some are even being honest with what they put out and show. They help us to keep current with what is happening.

    Of course there are some who this is their livelihood. They work directly for or very closely with certain airgun manufacturers, distributors or dealers. It does not take long to spot them. They will rant and rave about an airgun and quickly gloss over its failings.

    Golly gee whiz! That was a long spiel! Someone take this keyboard away from me!

  6. GF1,

    I too have thought much about that Viper Express. The cost of the shot shells are prohibitive, but they can be reloaded. It uses #9 and that is OK, but I have also thought of #12.

    It is a close range toy and would be fun to play with, but it is right expensive. If I could pick up a used one for about $100, I would.

    I am very curious about its accuracy using slugs (pellets). I know how to make that trigger “decent”. A dot sight on there may make it pretty nice.

      • I did not remember it, but I have now. Where is Part 4 where reloading these shot shells is described? 😉

        No, I would never shoot an animal with this. Hunt squirrels?! It is a good thing I was not there. I would have used his butt cheeks as a pattern board to demonstrate to others why you should not hunt anything with it.

        Now with #12 or Kosher salt it might be great for carpenter bees. 🙂

    • RR-

      I just took delivery of a new Viper Express yesterday. I’m still giggling from my first sight of the shotshells. I’m working out a game to use this gun ‘productively’. It utilizes the Daisy Rocket Shot soda can thrower. It may require two shooters. One to trigger the trap and one to shoot the can with the Viper Express.

      I also ordered a tin of lead .22 round balls. That will make my ‘spread’ of round ball shooting experience from .22 to .735 in my Land Pattern muskets.

      • Paco,

        LOL! A .22 smoothbore. You should be right at home with it. Please let us know how it does with the RB and other diabolos.

        I am hoping to get my hands on a .58 or .62 replica Virginia “Poor Boy” rifle. Black powder is a “blast”. This Viper will help to make you smoothbore shooting a bit more economical.

        Once you get it, get a 2.5mm x 8mm or 10mm to replace the sear engagement screw. Be careful not to turn it in too much or your trigger will become dangerous. Give it a good bump test.

      • Paco
        Cool. I would like to hear all about it.

        If you can post some pictures of some patterns you shoot with it and at what distances.

        I have debated getting one for the longest time but just never did.

      • Paco
        Me and the kids do that with our rocket shot.

        One of us would take and shoot at the rocket shot with a single shot air gun while me and the other daughter would shoot at the can in the air with our 1077 and WildFire.

        Pretty fun stuff. You know what we need to try that with the Wingshot ll I got. Why and the heck haven’t I done that yet. Well now I know what I’m doing today. 🙂

  7. Just because I don’t know any better, is there a way to put the spacer at the rear of the spring instead of the front (piston) end? Maybe between the spring guide and the threaded bushing?

  8. Tom I have so thoroughly enjoyed your writings on the Marksman 70. This combines two big contributing factors to me becoming an air gun collector. My adult experience with air rifles began with the gift of a well-loved marksman 70 in .22 caliber……. In post Katrina New Orleans. With that 19-in long barrel and it being well broken in….. I can cock it with my index finger. After having read this it seems high time I take a peek inside. Of course first we need a trip over the crony.
    To bookend my interest in the Marksman 70, Derrick was wonderful enough to not only source me a marksman 70 l n i b, but also to do all his special tuning magic….. And to top it off blog at every step of the way. Thanks again Derrick! And of course thank you bb Pelletier.

  9. BB
    The whole trick to this cutting the spring tuning is only cut as much spring off as needed.

    What to do is only cut about a inch off at a time and watch for a velocity increase or drop.

    If your velocity drops right off the bat then there is probably no reason to go any further. Other than if your velocity is higher than you want. Then the object is to cutting your spring to get the velocity you want. You should still end up with a smoother shooting and easier to cock gun.

    But here’s the real trick. And this is starting with a different new gun that hasn’t had the spring cut yet.

    The same applies is to cut a inch at a time off and see what happens and watch to see if the velocity stays the same or increases. The thing to do is cut another inch off till you see the velocity slow down or speed up. When it slows down then stop and put like only one washer in to bring the velocity back up.

    Now if you keep cutting a inch off at a time and keep seeing a increase in velocity each time then cut another time and keep watching for the gun to slow down. If it does shim back up with only one washer and be done.

    The whole idea is to get rid of the spring that isn’t making any power and stop cutting the spring when you see the velocity drop.

    And don’t worry if you end up at zero preload or if you still have preload. The trick is getting gun to perform where you want without having to remove to much spring and drastically shim back up like what happened with this gun you just did. Just like to much preload isn’t a good thing. Neither is too much shims.

  10. BB
    Forgot. This doesn’t sound right. How can the fpe be more with less velocity and the same pellets used.

    “715 (15 f.p.s.)….746 (12 f.p.s.)…”

    This at the begining of today’s report.

    Oh never mind. That’s the velocity spread I suppose. Scratch that.

  11. Hey RidgeRunner,

    I remember reading about the GAMO Shotgun when I first found Tom’s PA blog after having lost contact when the Airgun Letter folded and the Gaylords absconded to Texas. I read all the back posts and that one made me mutter gamo, gamo, gamo; just like reading about hunting pigs with a gamo .177!
    The Brand lost any of my business forever with the lack of respect for game and even vermin which are living things that deserve a fast kill.
    I like your idea of showing folks the patterning on these inadequate tools for ethical pesting and just intolerable implements for hunting.

    Whey hunt squirrels with a scattergun anyway!

    End of Rant!

    shootski

    • Shootski,

      LOL! My first airgun was a Gamo CFX. I actually bought it as BB gave it a pretty high rating. At 25 yards it was stunningly accurate IF you could deal with the hold sensitivity, which was incredible. It is a sad thing that Gamo is such a major player in the world of airguns.

      As a general rule, I like marketeers even less. When you combine marketeers with a substandard product, you have a disaster in the making.

  14. Well guess what I happened to see today for sale but a new style stock hw50s in .22 caliber.

    It’s used but was only $259.00 and is suppose to be in excellent condition.

    Almost posted it here on the blog who had it for sale. The more I thought about I said nope I’m getting it.

    I had a 50 with the original stock that was the model right before these new ones and it was a good shooting gun. So interested to see how these new ones are.

    What I’m wondering is if they are still installing the anti gald strip. My old 50 had it but some people said theirs didn’t. We’ll see.

  16. Here is a thought, for the folks who cannot decide between 30S and 50S. First thing first, the query wouldn’t matter, because anybody who has that question in her head will eventually buy them bought. But if you have to choose one for the moment, then I’d say go with a 30S. With a little extra $s on the price tag of 50S, you can buy a 95; especially if you are planning to install a highpower tune kit in a 50S, then why bother while you can simply enjoy a 95? 95 is not prone to galling either, another plus. I think 50S comes into play for the folks who cannot decide between 30S and 95, so comparing 30S and 50S defeats the purpose of 50S, I assume.

    • Fish
      Here is something I think your missing when your comparing the 95 to the 50 and 30.

      The 50 and 30 is a lighter gun than the 95 and smaller.

      Plus does the 95 come in .177 caliber?

      Here’s the point. The 30 is a over all light easy to handle gun. It can be tuned up if needed.

      The 50 is also a light easy to handle gun. It makes good power and can be tuned up or down

      The 95 is getting into a bigger gun which makes it only appealing to bigger shooters. Yes it can be tuned down. But it won’t handle like a 30 or a 50.

      Here’s the thing. The 30 is one of those out of the box guns that is enjoyable to shoot. Same with the 50 with a little more power.

      From what I see of the 95 is getting closer to the magnum springer than like the mild calm fun to shoot 30 or 50.

      And what you think.

      • Great points. Agreed with all.

        A few additions though.
        95 comes with .177 – Were you testing me or something? 🙂

        95 being a tad bit heavier, I think, makes it better – less recoil with 12 fpe tune down. Also a question for you, how harder to cock a 95 than a 50S? Another thing, the galling issue that might occur with 50S. I, personally, would have difficulty coming to the bottom of it – would be such a bummer.

        I don’t think 95 is magum at all. It must be as big as a 27, I’m guessing – not that bad at all. It shoots an average weight .177 at about 950 fps, right at the fastest possible sweetest spot for that cal pellet. You can get a bit heavier pellet and shoot at about 800 fps. Relatively heavier .177 leaving the barrel at around 800 fps, less prone to wind straight projectory and accuracy. The original powerplant 95 must be a little hold sensitive, and I assume its screws might need a little loctite support.

        Now, all these are spec based armchair observations. I would love to hear realtime owners’ comparing experiences.

      • See the chrony results for .177 95 here. Not exactly a magnum, I think. 10 gr. pellets leaves the barrel at about 800 fps. Okay, pushes the borders of a magnum, but it’s just bringing the .177 pellets at their fastest sweetest spots. If a 10 gr pellets leaves right under 800 fps, then no barrel cleaning, no breaking sound barrier, and best straight projectory with least wind effect possible. Simply the most power I would like for .177 pellet.

        But…

        • Fish,

          A good general rule to keep in mind for sproingers is “If you increase the power, you increase the hold sensitivity”.

          Over the years many things have been tried to reduce this, most common of which is mass. There is a ratio, most likely exponential, of output power versus mass of sproinger, but I do not know it. Even then it will not be a fixed number as there are many other factors that can come into play.

          • RR,
            “If you increase the power, you increase the hold sensitivity”

            Agreed, but you’ve got to also add the weight in the equation as well, I think. A 95 with a 12 fpe tune down must be less hold sensitive than a factory 50S.

      • Gf,

        Now, I think about what you said, and I start to agree with you. Especially for a .177 guy like me, the question would be 30S or 50S – contemplating about 95 would be redundant. Both has to be bought at the end of the day, no other way around. 30 for casual plinking fun, and 50 is for longer range serious shooting.

      • Think FM is enjoying his 95, vertical challenges notwithstanding. Wish the eyes were better to maximize the enjoyment but the answer to that is to work on technique and compensation strategies. Artillery hold definitely required. FM learned that from this blog and all ye good airgunners’ advice and tips.

        Eventually will come time to see how an already good air rifle can be improved, but most of the improvement has to be directed onto FM. “Mild” Loctite for the stock screws for starters, definitely.

          • You could say that but nothing bad; very nice trigger which FM has left alone. If it ain’t broke, don’t fix it. Bought it in May, as a self-given birthday present. It seems to like H&N Field Target Trophy Green 9.57 gr pellets best; at least those give me the tightest groups at 25 yards.

            Crosman Premier 14.3 gr hollow points are ok or at least good enough for pesting purposes. The worst performers so far are the Gamo Redfire 15.4 gr .22 cal pells, but again, these are mostly reserved for the thicker-skinned pesties around here.

            Not done in the quest for the best pellet and perhaps down the road maybe a little TIAT will be in order but for now, things are very satisfactory in Fawltyland. 🙂

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