Diana Mauser K98 PCP rifle: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

Diana Mauser
Diana Mauser K98 PCP.

Part 1

This report covers:

  • Fill
  • JSB Exact Jumbo Heavy
  • Fill to 200 bar
  • Discharge sound
  • Discussion 1
  • Beeman Kodiak
  • Pellet feed with the single-shot tray
  • H&N Hollow Point
  • Discussion 2
  • Trigger pull
  • Summary

Today we test the velocity and power of the Diana K98 PCP rifle. According to the description on the Pyramyd Air web page, this is a 26-foot-pound air rifle in the .22 caliber I am testing. This information helps me select the right pellets to test. A pneumatic in this power range is probably best with medium-weight to heavyweight pellets, though I will also test lightweights, just so we know.

Fill

I tried to fill the rifle to 200 bar/2900 psi — the recommended fill pressure, but I waited an instant too long to shut the tank valve and the fill went to 3,000. It’s only 100 psi more.

I will comment now that Diana does not supply a plug to cover the fill port, to prevent dirt from entering and getting in the gun. It won’t affect me because I am testing indoors, but if you want to carry the rifle outdoors, I recommend finding a way to cover that hole. Even a piece of duct tape will work.

The rifle has a magazine that I will also test, but for most of today’s testing I plan to use the single shot tray that comes with the rifle. Let’s get started.

JSB Exact Jumbo Heavy

I got a strange string from the JSB Exact Jumbo Heavy pellet. I will show it to you and then discuss it.

Shot……….Vel
1…………..794
2…………..812
3…………..827
4…………..840
5…………..842
6…………..851
7…………..did not register
8…………..869 onboard pressure gauge read 2800 psi.
9…………..871
10…………876
11…………869
12…………871
13…………862
14…………857
15…………846
16…………832
17…………816
18…………819
19…………803
20…………789
Stopped.

Okay, this is a very peaked velocity curve without much of a flat spot. At the highest velocity of 876 f.p.s  on shot 10 this pellet generates 30.9 foot-pounds. That’s well above the 26 foot-pounds it is rated for. With this pellet that energy would be developed at 804 f.p.s. So, if I take that as the standard and accept all 20 shots shown, the rifle got 20 shots that had an 87 f.p.s. spread in velocity.

Fill to 200 bar

I think that spread is too large for shooting anything past about 20 yards. What would happen if I filled the rifle to the recommended 200 bar/2900 psi and shot the same pellet? I was very careful to do that on the next fill. Let’s see what this same JSB Exact Jumbo Heavy pellet does.

Shot……….Vel
1…………..857
2…………..868
3…………..867
4…………..880
5…………..878
6…………..878
7…………..871
8…………..867
9…………..856
10…………848 gauge read 1400 psi
11…………846
12…………831
13…………818
Stopped.

Diana Mauser gauge
After shot 10 the gauge looked like this.

This time I got an 11-shot string that went from a low of 848 f.p.s. to a high of 880 f.p.s. That’s a spread of 32 f.p.s. It’s a lot tighter than 87 f.p.s. At the high velocity the energy generated was 31.18 foot-pounds at the muzzle.

Discharge sound

This Diana Mauser is a suburban backyard air rifle. When it fires it sounds like a mouse cough! The sound is negligible — maybe a 1.9 to 2.0 on the 5-point scale.

Discussion 1

It seems what we have here is a PCP that’s much more powerful than advertised, and also short on breath. It reminds me of the Korean PCPs of the 1990s that got 10 shots and had an equally large spread. Their reservoirs were larger so they put out 65+ foot pounds at their top, but the performance curve is similar. If this isn’t a good example of why a chronograph is an important tool for the airgunner I don’t know what is.

Given the power that’s available I tested a heavier pellet next.

Beeman Kodiak

The .22-caliber Beeman Kodiak pellet is obsolete, but it’s identical to the H&N Baracuda. It weighs 21.14-grains. I carefully filled to 200 bar again and shot the following string.

Shot……….Vel
1…………..798
2…………..791
3…………..816
4…………..823
5…………..830
6…………..830
7…………..826
8…………..833
9…………..824
10…………824
11…………811
12…………798 gauge read 1400 psi
13…………786
Stopped.

At the highest velocity this pellet generated 32.35 foot-pounds. I’m saying there were 12 good shots in this string that ranged from a low of 791 to a high of 833 f.p.s. That’s a spread of 42 f.p.s. At the lowest velocity the energy developed was 29.38 foot-pounds. Because of that, if you stop shooting at 12 shots after a 200-bar fill with this pellet in this rifle, you will be at or above 30 foot-pounds, which is well above the advertised energy.

Eight of the shots in this string (shots 3 through 10) are within 17 f.p.s. of each other. The rifle does seem to like the heavier pellets over the lighter ones.

Pellet feed with the single-shot tray

I noticed that if I held the rifle with the muzzle up while loading, the pellet could slide back on the single-shot tray into the receiver. I took a picture for you, but I don’t think it is a problem. The groove for the pellet continues on back into the receiver and when I pushed the bolt forward the pellet came out of the receiver and loaded correctly every time.

Diana Mauser pellet in receiver
When the muzzle is held up the pellet can slide back on the single-shot tray and disappear into the receiver like this. That’s the nose of a JSB dome. It still seems to feed well.

H&N Hollow Point

I was out of .22 Hobby pellets so I substituted 12.65-grain H&N Hollow Points. They are no longer available but they should give you an idea of what a lighter pellet will do. I filled the rifle to 200 bar. I will tell you right now that this string was a real surprise!

Shot……….Vel
1…………..991
2…………..976
3…………..972
4…………..975
5…………..972
6…………..955
7…………..964
8…………..961
9…………..942
10…………935
11…………930 gauge read 1400 psi
Stopped.

Wow! I didn’t expect that! An almost straight drop from the first shot to the last. At the highest velocity this 12.65-grain pellet generated 27.59 foot-pounds. At the slowest velocity of 930 f.p.s. it generated 24.30 foot-pounds. This string of 11 shots varied by 61 f.p.s. I think the Mauser PCP doesn’t care for lightweight pellets!

These hollowpoints have a sharp shoulder that caught on the transfer port twice while shooting this string. When that happened I backed off on the bolt and tried again and the pellet went in both times.

Discussion 2

Well, now we know that there are just 10 or 11 shots on a fill — depending on the pellet. We also know that the rifle prefers heavier pellets.

Testing the magazine and shot count

Time to test the function of the magazine. I tested it with the 18.13-grain JSB Exact Jumbo Heavy pellets for which we have a good baseline. And in this string I got another surprise — more shots on the fill. Is the rifle breaking in?

Shot……….Vel
1…………..837
2…………..839
3…………..850
4…………..855
5…………..863
6…………..874
7…………..874
8…………..880
9…………..877
10…………873
11…………865
12…………857 gauge read 1400 psi
13…………849
14…………839
15…………828 gauge read 1200 psi
16…………817
17…………did not register
18…………785 gauge read 1100 psi

This string gave 15 shots that stayed within 52 f.p.s. Fourteen of them are within 43 f.p.s. Those 14 shots were between the fill of 2900 psi (200 bar) and the reading that was just above 1200 psi. The rifle may be breaking in and may get even more shots per fill than what we see here after more shooting.

Will it continue to get more shots per fill? I don’t know but it’s very possible. There could be as many as 20 good shots on a fill when the gun is fully broken in. I believe I will return and test the velocity after the accuracy testing is complete.

Trigger pull

The Mauser PCP trigger is 2-stage. Stage 1 is light, at 1 lb. 5 oz. Stage 2 though is heavy and creepy. It breaks at well over 12 lbs. which is the limit of my electronic gauge. It doesn’t feel that heavy but I measured it repeatedly and it pegged the gauge every time. It’s no target trigger for sure but I don’t think it will bother most shooters if they know what to expect going in.

Summary

Well, the Diana Mauser PCP is certainly a different air rifle! It has way more power than advertised and is a bit short on the shot count. I will return and test that again after the rifle has a lot more shots on it.

The rifle feeds smoothly from both the magazine and the single shot tray. Domed pellet seem to do the best.

If the Mauser is accurate it will make a good hunting or pest rifle, as well as a good general shooter. Just carry a small air tank to keep it filled.

I plan to shoot targets next. I will use the open sights and shoot from 10 meters. Stay tuned!

41 thoughts on “Diana Mauser K98 PCP rifle: Part 2


  1. BB
    The trigger sear adjustment, “I will look at that in the next report”. What change is there?
    I really like the setup with the small air tank out of sight. Good compromise for a K98 replica, and others to come?
    Bob M



      • BB
        I certainly admire your dedication to the job. Can’t fault you for spending too much time providing us with information. You are a far better man than I when it comes to time management and getting things done. Retirement has spoiled me for sure.
        I’m really just curious about that adjustment and if it has any effect on the trigger pull and what setting is best.


  2. B.B.

    A backyard plinker? With only 10 good shots, that would get old real fast!
    Would a regulator give more shots?
    Maybe they could put another air reservoir in all that unused space of the stock?

    -Y



    • It also seems way overpowered for a backyard plinker, but that’s my beef with the underlever Diana Mauser as well (and the upcoming Air Venturi underlever M1A).

      The Canadian versions have been detuned to 495 FPS (but presumably have no baffles), so I wonder if they might be worth a look in terms of shot count


  3. BB,

    In the “Fill” section,… 200 bar/2900 psi

    In the “Fill to 200 bar” section,…. 200 bar/2800 psi

    A quick check shows the 2900 to be correct.

    Interesting rifle. The replica collectors should be happy.

    Chris


  4. Over 12 lb. trigger…WOW How difficult will it be to get reasonable groups? I have a hard time thinking you’ll get decent groups without tuckering out after a couple of shot strings. I know I couldn’t do it in one day without a nap between strings. Maybe one before I started and one after too, just because.


  5. From the numbers, the Diana Mauser K98 looks as it was intended to be a replica that happens to shoot rather than an airgun that looks like a K98.

    Still, it is a good looker (if you are into replicas – not my bag) and would be a fun casual can-plinker for close range use.

    By the shot count and velocity spread I think that it might be better if it was tuned to shoot light pellets at a lower velocity. Cans at close range don’t need a lot of power to kill, dropping to 20ish fpe would probably triple the shot count.

    I’m not a trigger-snob and can happily work with heavy triggers but “12 pounds and creepy” is going to be challenging to shoot for accuracy. You would think that Diana would know enough about triggers to do better than this, there must be some burrs or out of spec parts in the trigger to be that bad.

    …Just a couple of random thoughts.

    Hank



  6. BB,

    I would strongly suggest that you see if that trigger can be adjusted to something more reasonable. That twelve creepy pounds is killing this thing.


  7. I do not like to make negative comments but in this case I cannot shake a feeling of disappointment in the performance of this rifle, particularly with names like Mauser and Diana attached to it.

    I agree with others that with a balanced valve – or better yet, a regulator – and a lower output around the 12+ fpe level this one could be a delightful backyard can exterminator. But even them, there is the trigger. Bummer.

    This is a particularity sad because I always liked Diana rifles, but more important, because the first high power rifle I shot when I was 14 or so – under the supervision of a serious instructor – was precisely a Mauser. It was a military Model 1909 in 7.65mm, quite similar but longer than this one. I didn’t make the high school rifle team but it left a really good impression of its design quality, besides a sore shoulder once or twice.

    Henry


  8. B.B.,

    Oh! Say can you see…How far the Dark Side has come!
    With a 100cc reservoir at 200BAR getting 500-600FPE of energy using 2/3 the fill pressure! And, We the People are complaining about the shot count! Lol!

    I bet a good PCP tuner could flatten that curve to 12FPS, keep the power above the rated power, and get your 18-20 shot count.
    Also, how would this Hunter’s rifle do with a hollow point slug?

    [This or That?] 1st Para: “[The] helps me select the right pellets to test.”

    I hope it is accurate!

    shootski



    • Shootski,

      Speaking of slugs. Last week I was able to try four different slugs in my RAW at 100 yards. The wind was mostly from my back but it was not steady in direction or speed so It was a. bit stressful trying to wait for decent conditions.

      I shot a ten shot group using JSB Redesigned monster 25.39. grain pellets first to have a comparison. The group was about 1.75 inches so I know the wind was not helping. I had shot groups less than that but not by too much.

      I shot the FX hybrid slugs .22 grains first. They looked the best out or the tin. 5 shot Group 1.42 inches

      All the H&N slugs in this test were .218 caliber 5.53 mm.
      Next I shot the H&N 21 grain slugs. 5 shot group 2.2 inches

      Then the H&N 23 grain slugs. 5 shot group 1.45 inches

      Last I shot the H&N 25 grain slugs. 5 shot group 1.01 inches.

      The H&N slugs were snug but not too tight to seat with my finger almost all the way. The FX slugs were so tight I could only seat them just over half way. The FX slugs may have been slightly deformed as the probe forced them into the leade.

      The day was not the best but I think the H&N slugs were just as good as the FX slugs in my RAW. I may order some of the H&N slugs in 27 and 30 grains. Also a tin in .217 caliber should be tested.

      So it looks like my RAW HM1000x LRT is capable of 1 moa at 100 yds if I can do my part.

      It would be good to hear others experience with slugs.

      Don


      • Don,

        Shooting at 100 yards is always exciting. Plus,… you are trying out slugs,.. which (should?) put you at an advantage at longer ranges. Do you happen to know the fps’s you are getting and is the barrel a faster twist rate (more slug friendly) or is it a standard twist barrel? Does RAW do slug specific barrels,… like FX does?

        I have a .25 Red Wolf HP and a .25 M-rod,… but have not tried much in the way of slugs yet. The HN Grizzlies did not do as well as the 25.39 pellets.

        Best wishes going forwards!

        Chris


        • Chris U,

          I forget the twist rate. With pellets I was getting 1007 fps with 21 gr pellets and 824 fps with 34 gr pellets. I will have to try and measure the twist rate next week. They have both rifled and polygonal barrels. I think mine is polygonal.

          I think the slugs can be designed with a radius of gyration that makes them stable at pellet spin rates. These slugs are not long compared to pellets and have a dence compact shape.

          Don


      • Benji-Don,

        I can see your smile all the way to here!!!! Under two MOA with any shooter is something to be proud of for most shooters. Getting ONE MOA is a sign of Marksmanship; anything under is just MOCCA BUTTERCREAM icing on the cake!

        The smallest bullet (SLUG) I shoot is .43 gn in .25 cal. and over 85FPE so i need to get my Marauder some of the new .22 Slugs. To much time with the Big Bores ;^)

        Nice shooting!

        shootski



  9. I was out shooting with my Canon EOS Rebel T5i just a bit ago. This buck was just laying there chewing on his cud. I must have shot him almost ten times from about 25 yards away. He did not stand a chance.


    • RR,

      I have had 3 fawns and a mama hanging around for about 3 weeks now. The 3 appear to be the mama’s. They can have 1-3, with 2 being the most common. They feel safe around here I guess. If I am out and looking,.. I can see at least some of them on a daily basis. Today,… all 4 were in the yard and I was sitting in a lawn chair 25 yards or less away. 15-20 minutes. Pretty cool.

      The baby’s are real good at hiding. I was clearing some wooded area awhile ago and one was (inside) a hollowed out down tree. I have seen them in downed trees/brush on several occasions.

      Chris



  10. Wow! I will say that I am not at all impressed with the large fps spread, nor the 12# trigger. It’s all show and no go. Nice gun to hang on the wall. 🙂 My Gamo Urban only has 105cc reservoir but I get 25-30 shots with a fps spread of only 20 fps. I usually only shoot two mags, 20 shots, before filling. The fps spread for 20 shots is only 15 fps.
    I am wondering if the K98 has an adjustable hammer spring. It would appear that the rifle is wasting a lot of air to get just a few more ft-lbs of energy. Maybe backing off the hammer spring would yield a flatter curve and only slightly less ft-lbs of energy.
    Geo


    • Geo,

      It is of concern that B.B.s example is so far OVER the rated energy claim? How much variation i wonder in the run of guns from the manufacturer?

      Hammer Spring preload to my thinking is reserved for fine tuning for the chosen ammo/range to get best grouping.

      I’m betting a stronger valve return (close) spring would do a better job with most appropriate weight ammo and a very slightly smaller TP (Transfer Port) to flatten out the peak in the curve. But first i would shoot 200+ to break in this powerplant before speculating more. That has been my experience with all the unregulated balanced valve PCP I have ever owned. I think you know my opinion is to go with No Regulator because i want full or close to full power for hunting and shot count be darned. After all i am perfectly happy with two shots at 500+ FPE.

      shootski


  11. I think the R10 is a better ‘K98’ than the Diana is; especially with the PG3 kit. What a beauty!
    Dont put any grease on the piston sear rod for that kit. slows it down.Cocks smooth as butter with new shoe too.
    No air required. love it.
    At least the Diana hits hard like the Mauser does.
    Rob


  12. “A replica that happens to shoot”

    Vana2 hit home with that statement. Most of what I own can be put into that category.

    A replica gun on the wall is far more interesting than a picture, and one that you can actually shoot only adds to the enjoyment of having one.
    Early on I collected a few non firing six shooters I figured I would never see in production again or care to pay the price for if they did return and then Airsoft started to replicate almost everything, and you could almost capture the handling and shooting experience. And now airguns are jumping in the game of replicating firearms in a big way. Right down to the ammo used.

    I have this K98 Replica PCP and have no plans to shoot it for any particular reason other than replicating the experience of shooting one. So it’s performance in filling any particular shooting category is not a big thing to me. I have many other working airguns that can be used for their intended purpose.
    It’s not perfect but the power and sound certainly add to the experience even if its far from shooting the real thing.
    I don’t think too many people would claim shooting something like a real 308 cal rifle for an hour or so is really fun. A hell of an experience but fun? Perhaps for the first time or so.

    Now my gold plated and engraved Colt SAA pistols are replicas and collectables so I may never shoot them. Instead I just got some base or refurbished models to use.

    So, do we now have a relatively new ‘replica’ airgun shooting category that has, shall we say, less defined requirements for use other than the fact that it shoots and identifying its performance? Why else would they not provide a windage adjustment for the sights?
    Just shooting a ‘Replica’ is a major reason for getting one and since it is not really intended to fill any particular shooting category or to be used on a regular basis, other than satisfying collectors urges, superior performance would just be icing on the cake.
    Now if you are paying top dollar for it, it should really perform well too.
    Bob M


  13. Shootski
    I’m sure there was a lot of trepidation in the decision to manufacture a replica airgun that may only appeal to a minority of hardcore (PCP) airgunners. That probably resulted in a lot of compromise in designing and marketing it. The break barrel and airsoft version were already out there in competition.

    I’m just grateful they actually ran with it. I’m not sure if the replica and PCP airgunners are a stable customer base.
    Small steps in this replica category may result in some outstanding airguns in the future if it continues to be profitable.
    Glad my point above came across well. Thanks,
    Bob M


  14. Let me admit to being a spring-piston shooter, so, yes, I am biased. However, I just don’t “get it” with the PCP version of the K98. BB’s review showed a low shot count and wide velocity variation, albeit with a new rifle (here conceding that with use it might level out). When one looks at the spring version, one can see that the velocity is only 50 fps down from the PCP, but it will do that all day or until one’s cocking arm wears out.

    Yes, the spring version is single shot; so the advantage with follow-on shots, obviously, goes to the PCP in the short run. In the long run, however, which will get out more shots on an afternoon of pesting? Filling every couple of dozen shots is going to take one off target.

    The PCP, of course, offers less in the way of recoil and vibration and that is undeniable. However, having learned to shoot spring guns and having kept at it since 1989 makes much of the advantage, to me at least, moot. Once one learns the artillery hold, keeps the sight picture through the shot cycle, and allows the piece to rock and roll freely, the accuracy is not a problem (at least with a broken in springer).

    With the exception of really big bore airguns, that make springers really less than possible, I don’t get the point of the PCP K98, the springer shoots all day and more consistently, in my way of thinking, and one doesn’t need a nurse tank in the middle of the woods.


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