Diana 72 youth target rifle: Part 2

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1

Diana 72
Diana 72 is a youth target rifle from the late 20th century.

This report addresses:

• Cocking effort
• Velocity
• Velocity and consistency comparisons, depending on how the pellet is loaded
• Firing behavior and cocking behavior after oiling
• Trigger-pull
• Impressions so far

Some topics resonate with more readers than others, and this is one of them. I heard from many Diana model 70 and 72 owners when Part 1 was published, and I hope to hear from more with this installment. New blog reader Harryholic from the UK had just received a new-old-stock model 72 when Part 1 was published. Searching for information on his new rifle, he stumbled across our blog.

His new rifle is one that hadn’t ever been fired, apparently. It was still in the original Diana packaging based the pictures he published online. Unfortunately, that means it has the old Diana piston seals that dry rot with age. His new gun heeded a resealing before he could even fire the first shot. While he’s arranging to have that done, I’ll test our 72 that was resealed last year. It should have pretty close to new-gun performance.

Cocking effort
This rifle is a converted air pistol — we learned that in the last report. I recall my Diana model 10 target pistol needing about 35 lbs. of force to cock. The old Air Rifle Headquarters reported the velocity of a broken-in model 10 as close to 500 f,.p.s. with lighter lead pellets. I will presume they mean something like RWS Hobbys.

A model 10 has the same poweplant as the model 6 pistol that on which this rifle is based, so I’ll use the cocking effort and velocity for the model 6, as well. I believe a model 6 in good shape should launch a Hobby pellet around 475 f.p.s. That would also be my guess for the model 72 rifle. We shall see.

As for the cocking effort, we learned last time that the 72 has a longer barrel shroud (13-3/4 inches, compared to the 7-inch barrel on the pistol) that extends the lever used to cock the rifle, so I expected the cocking effort to drop off to about 20 lbs. When I measured it on my bathroom scale, it was more like 16 lbs., though some stiffness in the cocking linkage did make the needle spike up to 20 at times. I think this will smooth out as the rifle wears in.

Velocity
I think I learn as much when I chronograph an airgun as I do when shooting it for accuracy. The things I learn aren’t always what I expect, though, and today’s test demonstrates that.

RWS Hobby
I started the test shooting the 7-grain RWS Hobby wadcutter pellet. I like using Hobbys because not only are they very light and give high velocity numbers, but they’re also well-made and often quite accurate.

On the first string, I noticed something remarkable. I’m going to print the string here, so you can see what I saw:

Shot Vel
1     438
2    406
3    391
4    387
5    377
6    366
7    362
8    349

After shot 8, I stopped to evaluate the gun’s performance. Each shot was going slower than the last. The 72 is a spring-piston rifle, and it honked a bit when cocked. So, I deduced the piston seal was dry. I oiled the seal with a few drops of RWS Chamber Lube and then returned to the string.

9    414
10    399

The average for this string is 389 f.p.s., but a lot of the reason for that is because of the velocity loss. This rifle was just rebuilt. It came back to my friend Mac just a few weeks before he passed away, so he never shot it. Therefore, I’m the first person to shoot it since it was rebuilt. I’m breaking it in.

After the first string, I oiled the chamber, again, with about twice as much oil as I used before. This time, I shot 10 Hobbys at an average 427 f.p.s. The spread was from 399 to 449, so 50 f.p.s. Obviously, the rifle needed to be oiled. And notice that my original estimate of the expected velocity was too high.

Next, I tried deep-seating the pellets with the Air Venturi Pellet Pen and Pellet Seater. This gave an average velocity of 424 f.p.s. The spread went from 401 to 461, so a total of 60 f.p.s. From this, I have to deduce that deep-seating Hobby pellets does not accomplish anything.

H&N Finale Match Pistol
Next, I tested the rifle with H&N Finale Match Pistol pellets. Seated deep, these averaged 393 f.p.s. The spread went from 376 to 405, so 29 f.p.s. That’s a lot tighter than the Hobbys.

I tried these same pellets seated flush. This time they averaged 456 f.p.s. The spread went from 450 to 462, so just 12 f.p.s. They’re both faster and more consistent when seated flush with the breech (not pushed into the barrel by a pellet seater).

RWS R10 Match Pistol
The last pellet I tried was the RWS R10 Match Pistol pellets. These weigh 7 grains, just like the Hobbys. Seated deep, they averaged 395 f.p.s., with a spread from 365 to 414. A max spread of 49 f.p.s. Seated flush, they averaged 429 f.p.s., and the spread went from 404 to 446. That’s a total of 42 f.p.s. Again, the pellet went faster and the spread was tighter when it was seated flush with the breech.

Note the velocities
A couple days ago, someone asked me if I ever experienced a heavier pellet going faster and with more consistency than a lighter pellet in the same gun. This test demonstrates that phenomenon. The 7-grain Hobbys went an average 424-427 f.p.s., while the 7.56-grain H&N Finale Match Pistol pellets averaged 393-456 f.p.s. When seated flush, these were the fastest pellets in this test, as well as the heaviest pellets.

Firing behavior and cocking effort revisited
I told you the rifle squeaked when cocked. At the end of the test, it still squeaked — but less than before. Also, the cocking effort seems to have smoothed out a bit. I measured it, again, and this time the needle deflected from 16 lbs. up to between 18 and 19 lbs., but it was so close I can’t tell if there has been a real reduction or not.

The rifle fires dead-calm regardless of which pellet is loaded or how it’s loaded. But flush seating seems to be best, so that’s what I’ll do.

Trigger-pull
The 72 trigger is 2-stage, but not as crisp as I remember the trigger of my model 10 pistol. Stage 1 stops at stage 2, but then stage 2 has movement that can be felt. The net feeling is a trigger that has no second stage, though I know this one does and can feel it if I really try. The trigger breaks at 33 oz. consistently.

There’s a good reason for this trigger to be mushy. The linkage is very long because this is a pistol in a rifle stock. I looked for trigger adjustment instructions on the internet and couldn’t find any, so in the next report I’ll show you the trigger and describe how to adjust it in detail.

Impressions so far
I like the little rifle — not quite as much as I thought I would, but perhaps I’m objecting to the stiffness of the rebuild that just needs to be broken in. Once I get the trigger where I want it — if that’s possible, I may warm to it some more.

47 thoughts on “Diana 72 youth target rifle: Part 2

  1. Good morning, friends!

    I just wanted to tell you that yesterday, for the first time since I got sick, I was able to get to my basement, pull out my LP-10, and start shooting!!! I’m weak, so my results were awful until I pulled out a bench rest. Then I got lots of nines and tens. When I went back to unsupported shooting, I got eights and nines.

    The pistol had to be rezeroed, of course, but it held the air I left it with last summer.

    I still need a kidney, but now we’re just waiting on the results of a blood test on my son. My daughter’s been approved, but her blood type is incompatible, so Hopkins is seeking a matched pair. Either way, we should be able to schedule something in the next couple of weeks and just wait for two operating rooms.

    And my latest cancer screens came back on 6 May and were 100% clean. I’m out of that woods!

    Thanks very much for your prayers and good thoughts.

    Pete


    • Welcome back Pete,Sounds like your life’s a lot like mine right now. Too bad you’re still not fixed.I hope things go well for you,m My Dad’s currently on dialysis and diabetic,I was a smoker until multiple strokes put me in the hospital for almost a month
      I’m still working on my arm,which bounced back into action all of a sudden Today!I wish you the best of luck,Sir
      Come back well soon!
      Reb


      • my brain was still misfiring last night when I made this comment so I didn’t get the whole thought out. I will try to finish it now.
        When my dad learned he needed a kidney donor, I was outta the running because I smoked, my brotherwas tested for compatibility.Now I am currently in the process of being completely nicotine free and considering being tested also. The thought of having any type of surgery is frightening to say the least but a transplant!?I can understand my brother’s apprehension,He just changed careers from locomotive engineer to loan officer overnight! While raising Aryn & Adyn alone( with Gramma for a babysitter,who is also now my nurse)But if it’ll save my Dad, it’s all but done once I have completely quitsmoking,and pending compatability testing.

        Reb


    • Pete good to here you doing good with the cancer. Or I should say without the cancer. :) Good for you.
      And you know there will be prayers with the operations.

      Was you glad to get some shooting in? And I like when I get to do some bench rest shooting. To me its just a more relaxed type of shooting. I hope you enjoyed your shooting session though. Good to hear from you and with good news at that.


    • Good to see you up and at’em again, Pete! I pray everything goes well with finding and getting the perfect match!

      /Dave




    • Pete,

      It’s great to hear from you again. I do pray for you daily.

      You are shooting about the same as me, and I have had three years of healing! So no need to apologize.

      Just keep pulling that trigger, sir!

      B.B.


    • Pete

      I so admire your courage in the face of obvious pain. So glad to know the tests are negative. My prayers are with you. Get well soon.

      Errol




  2. BB

    Like I said before, it has a home waiting. ; )

    Lately I have also been having a real strong urge to get my hands on a nice Diana Model 10. I know it won’t perform as nicely, but I could see it replacing Izzy’s spot.


  3. BB,
    If recoilless spring guns are shooting so smooth, why Weihrauch, BSA, Walther, and others produce them?
    The spring guns they make we have to tune them, to get them to have a smooth firing cycle. The only one that makes a recoilless is the Diana 54.


    • Joe,

      The day has come and gone for recoiless spring guns. They’re typically complicated and expensive. The Single Stroke Pneumatics quickly overshadowed recoiless springers. The market/consumer spoke.

      Although the 54 is recoiless to the shooter it has significant recoil to scopes since it’s a sledge type action. Personally, I wouldn’t put it in the same catagory as a giss or whiscombe type recoiless action.

      kevin


      • I believe the 54 is actually harder on scopes than the 52, simply because the recoiling part has less mass (since the stock doesn’t recoil).



        • The m54 gives a scope /both/ type of recoil… “powder” type recoil on the initial firing — as the receiver slides backwards just as firearm does, followed by a sudden stop (unlike a firearm) as the piston bottoms out (where regular spring gun’s main felt recoil is not the rearward push in counter to the piston, but rather the forward lunge when the piston bottoms out — on the m54, one has the stop, but any forward lunge would be a reverse slide motion).

          Firearm scopes are built for the rearward push, and a forward push (from normal spring guns) “unseats” the reticle tube [which is pressed against the front of the outer tube by a spring, so firearm recoil just presses it tighter -- but spring gun lunges have it slide backwards relative to the outer tube]).

          Based on my m54s original scope, it was the rotary torque that killed the scope — rotated the reticle tube some 5-10 degrees from “vertical”.


      • Kelvin,
        But B.B. told me that the reason the FWB 300S firing cycle is so smooth is because of the recoilless feature and not anything else. B.B. said that the tolerance of the internal power plant is very loose.


        • Joe,

          BB is correct. The FWB 300 is a sledge type action as well so it is recoiless to the shooter. The big difference between the 54 & 300 are power and this translates into recoil/movement to the sights/scope. Because of power the recoil on the 54 is violent.

          Kevin


        • Another little thing about the FWB 300 series is that instead of one spring, there are two springs end to end that are also counter wound so as to counter the torque of each other, thereby neutralizing the torque effect you can feel in many sproingers.




  4. I’m going to ask a silly question. I haven’t had one of these 72′s in my hand before so I don’t know.

    But what is that black button on the right side of the gun that’s a little forward of the rear sight. Is that the safety or do you push that to unlock the barrel so you can cock the gun?



    • GF1,

      I explained that round thing in Part 1. There is a picture of it there (third photo).

      That is the cap of the anchor point or trunnion where the two pistons are connected. Each piston has a geared rod and that cap covered the central gear that anchors both of them. It is a means of timing the pistons so they reach the end of their stroke at exactly the same time — thereby cancelling each other’s impulse.

      B.B.


  5. Hey BB,
    I think I remember you saying before that deep seating does not just effect velocity, but also accuracy. I’m wondering if you’re going to try seating variations when you perform the accuracy tests.

    Also, went back and watched your artillery hold video AGAIN. I had been pulling the rifle into my shoulder. Well, I ran two tests of 10 from 10 yards. Guess what? My groups tightened from a little less than a quarter to about half the size of a dime when I balanced the gun on the back of my wrist. You already knew that was going to happen though, right? :)
    Rob


  6. B.B.

    I need some advice Sir. Why does an air rifle give a lower velocity when a new piston seal (synthetic) & mainspring is installed than before. Also, the velocity is moving up gradually as it is shot. Does the seal need a certain time to reach peak efficiency?. Also is this specific to synthetic seals only? I lubed it correctly.

    Errol


    • Errrol,

      That’s a good question. Know that it doesn’t always work that way, but usually it does. That’s because the new seal is very tight and creates excess friction with the walls of the compression chamber. The lube I used in today’s report reduced that friction somewhat, but the wearing-in of the piston seal over time will do even more.

      Think of a pair of new leather shoes. They are tight and usually hurt your feet for awhile. But once they break in they fit your foot more exactly and then feel wonderful.

      B.B.


    • Errol,any machined surface requires a break-in period. you would be surprised at how rough a smooth surface actually is, but look at one under a microscope! During break-in period these “smooth” surfaces use each other to grind themselves down to a more level and smoother surface, this increases surface area contact which can mean different things.
      In instances with piston sealing rings this increases compression due to less blow-by between the cylinder wall and the ring. In other applications this may increase friction too much. That’s why we have tolerances( a measurement within acceptable parameters)
      Hope that helps
      Anyone, please feel free to add to this statement in order to further our education(s).
      Reb



        • I just wanted some explanation, of how this works, available for inquisitive minds. I used to explain this to every brake job customer I worked for, in order to keep them from rear-ending someone with their “new brakes”.


  7. B.B.

    Thank you Sir. You just are spot on as always. The new Seal was an original but WAS tight so it needs time to settle then. I was worried that maybe I did it wrong. It
    did 560fps before the replacement & now its doing about 470 to 480 up from 450. Its a Norica titan basic rated at 623fps new. Thanks again for explaining so clearly.

    Errol


  8. B.B., I know enough about pcps to know that the valve is critical, so there is obviously something to the Escape model. But this does remind of when I was buying my Anschutz. The choice was between the “famous” Model 54 action and the Model 64 action which was a lot cheaper. I asked about the accuracy of the Model 64, and the rep told me that it could put 10 rounds inside of a dime at 50 yards just like the Model 54. So, I asked him what was the difference between the two, and he just said that the Model 54 was better. I think he also said that it was stronger although this doesn’t seem to matter much with a rimfire. Anyway, I went with the Model 54 with a difference in price equal to a very fine airgun, so I must have been convinced. Also,, it seemed to me that skimping at this level did not make much sense.

    Matt61


    • Matt,

      That salesman lied to you. The heavier Anschütz model 54 is indeed more stable and therefore more accurate than the lighter model 64. The 64 is the basis of their sporting guns. They call it a hunting match repeater — a one-gun-does-all. I doubt very much that there are many model 64s that will put 10 rounds into a dime at 50 yards, but the model 54 should do it with a lot of good ammo types.

      You made the right decision.

      B.B.


  9. I don’t know you Pete but I praise God for your full recovery as I pray for it to happen.

    B.B. I think this is a very good looking youth rifle. If the accuracy is there I wouldn’t mind having one although it sounds like the model 10 would be better.

    G & G


  10. B.B.,I mentioned yesterday that I intended to order a Bricemount for my RedRyder.After a fruitless search,I requested that PA carry this,or a similar product and E-mail response. I have searched my E- mail and have found no response yet and will continue searching but I may have done something wrong so could you check on the status of my request?
    Purdy Please?
    Reb


    • Reb,

      I will ask Edith to look into it, but Pyramyd Air is pretty busy these days. It sometimes takes a couple days for me to get a response from them, depending on what the question is.

      As for their carrying the Bricemount, that is a pure business decision. If there is enough demand they may do it, but if this is a one-time thing, I doubt it.

      B.B.


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