Benjamin 310 BB gun: Part 5

by Tom Gaylord
Writing as B.B. Pelletier

Part 1
Part 2
Part 3
Part 4

A history of airguns

Benjamin 310
A Benjamin 310 multi-pump BB gun from 1952.

This report covers:

  • Smart Shot
  • 4.4mm balls
  • 4.45mm balls
  • Beeman Perfect Rounds
  • Darts and bolts
  • Airgun darts
  • Bolts
  • Airgun bolts
  • Bolt extraction
  • Not finished yet

Today I will almost complete the velocity test of the Benjamin 310 BB gun. Today we look at the velocity with lead balls and also with both kinds of darts. Lead balls are first.

I don’t plan on testing each lead ball exhaustively. If I find something interesting I can always expand that particular test. And I will exhaust all the air before each shot I record, so you know it is moving that fast on just those pumps.

Smart Shot

H&N Smart Shot measure 0.1725-inches, nominally. Here is their performance.


Notice that the amount of the velocity increase diminishes sharply after 4 pumps. If I were to pump the gun a 6th time I would estimate the shot would go out around 490-500 f.p.s.

Let’s try that and see.


As you can see, I did not test the gun before my estimate. I didn’t believe the first attempt, so I emptied the gun and tried it again. Without a doubt this BB gun tops out on 5 pumps with Smart Shot. It seems we learned that in Part 4, when 8 pumps shot slower than 5.

4.4mm balls

I tried 4.4mm lead balls next. I bought several tins of these a couple decades ago when the Haenel model 310 rifles were coming out of the former East Germany. These balls measure 0.174-inches, nominally.


I will guess that the same will hold true for 6 pumps with these, so I won’t try it.

4.45mm balls

I bought these H&N lead balls to test my Daisy Number 12 model 29 BB gun, but the plunger seal in that gun failed during testing. So now I have them available for other tests. They measure 0.1755-inches in diameter, nominally, so they are the size of the Air Rifle Shot that Daisy created in the early 1900s when they abandoned BB shot. Remember — this is the shot size Benjamin mentions in a lot of their literature, but they also call it steel air rifle shot. As far as I can determine, steel shot was never made in this size.


These results are interesting. They show this slightly larger and heavier shot traveling faster than the smaller stuff. I am guessing the reason is this shot seals the bore better. That will be interesting in accuracy testing. Now for the last shot — Beeman Perfect Rounds.

Beeman Perfect Rounds

Beeman Perfect Rounds are supposed to measure 0.177-inches in diameter, nominally, but I measured several and they came out at 0.1765-inches. That makes them both larger than the previous shot and also larger than anything Benjamin recommends for this gun. Let’s see what they do.


Wow! The largest shot also goes the fastest!

These shot will be interesting in the accuracy test. I will guess that the larger shot will be more accurate, but we have to test them all to know for sure. Remember the knuckleball? It moves around as it travels through the air because it doesn’t spin. Any one of these balls may do the same.

Darts and bolts

I have two kinds of darts to test — normal Air Venturi airgun darts and special Marksman airgun darts that they call airgun bolts.

I will try them with one pump of air and then add one pump for the next shot and so on. That will tell us where the darts and bolts stabilize, as far as velocity goes.

Since I am concentrating on the chronograph and I want to stop the darts as soon as possible after the last skyscreen, I put a hardwood cutting board in front of the regular backstop. Let’s get started.

Airgun darts



We learn a lot from this. First, airgun darts travel much slower than lead balls. That’s good because wait until you see how deep they penetrate.

Next we see that the velocity can vary a lot. Even after they have stabilized they can vary by almost 50 f.p.s. I don’t hold out much hope for their accuracy at anything past about 15 feet.

The darts came out of the gun with a lot of dirty oil on their fletching, so they won’t be pretty long. And they buried so deep in the board that I had to use pliers to extract them.

darts in board
At three feet the darts went deep into the cutting board. The blue dart in the center was shot number one. And yes, they all landed on an angle to the board.

I got them out with pliers. Because of that they aren’t going to last very long in this gun. Let’s try the bolts next.

Airgun bolts

The bolts were a little long to load, but their flexible plastic tails could be bent to get them into the breech. Let’s look at how they did under the same test conditions.

Airgun bolts


Bolts were more stabile in velocity, but they hit the cutting board at odd angles that suggest gross instability in their early flight. That means the accuracy is probably poor.

bolts in boards
This is how the bolts hit the board.

Bolt extraction

When I extracted them all 5 had bent tips. This was not from the extraction but from entering the board at high speed.

bent bolt
Every one of the 5 bolts has a bent tip.

That’s it for those 5 bolts. I threw them out because straightening their tips won’t make them fly better. I think these bolts are better suited to lower-powered airguns like the Marksman 1010 pistol.

Not finished yet

Well, this test is epic! The Benjamin 310 is so flexible that it handles more different kinds of ammo than any airgun I have tested — or at least I have tested more ammo in it. And I still have to test some pellets. So — we ain’t done yet!

41 thoughts on “Benjamin 310 BB gun: Part 5”

  1. I’m surprised you didn’t use a softer backstop for the darts and bolts. Something like your DIY rubber mulch shot trap (or really just lots of corrugated cardboard) might help extend the life of those projectiles.

  2. Very interesting test today.

    I have a springer question.

    I have a low serial number 1979 Uk made Webley Tempest in .177.
    It starts out at 395fps with 7.4gr wadcutters.

    After 15-20 shots it stabilizes at 308 fps +/- 4fps.

    Is it a seal problem or a Spring issue?

    It cocks and fires very smoothly,
    And doesn’t leak from the breach seal (toilet paper test.)

    Any help or suggestions are most appreciated.

      • B.B.,

        Thank you for testing the darts and bolts.
        I should think the bristle board would hold up best with just one pump based on, in my younger days, using a Benji SSP/MSP pistol(s) and long arm(s) with regulation bristle boards. The big it is flight stability. Your photos of the darts and bolts had me perplexed until the image of the bent bolt tips. Not having seen you pull them out I would guess that most of the leaning was due to the bent tip…that might be solved by the Bristle board.

        A good quick dartboard buying FYI: https://www.shotdarts.com/darts-info/dartboard-guide


  3. BB,

    Beautiful gun and nice tests wit hit, thanks.

    We use here a slab of lead as backstop for the darts. There is a whole competition with these darts using modified (smooth bored) Diana 66 Match guns. At 10 mtr they are quite accurate. I have one of those guns and I will see whether I can do some tests with it.

    I would like to see the bolts at ten yards as I have the impression that the angle which they display at the board is mainly due to the excessive impact. Are they much heavier than the rest?



      • BB,

        Thanks for the info. If I compute the foot-pound I get the following:

        lead lead steel
        Darts Bolts H&N smart 4.4 Haenel balls
        speed 203 256 577 569 580
        grain 14,3 9,2 7,4 7,4 5,1
        foot-pound 1,31 1,34 5,77 5,32 3,81

        A bit strange I would expect the bolts to be closer fitting than the darts and therefore faster but it is mainly the difference in weight which explains the speed difference between both.

        The slowness of the bolts and darts is not dependent on weight but on the form as the lead balls perform much better than the darts & bolts, but have a weight which is in between steel and bolts.

        So it is not the extra energy as the bolts & darts are heavier which makes the bolts deformed on entry but the elongated shape which induces them to fold.

        A different backstop and a longer distance may work better for the darts and surely for the bolts. I would give the bolts another chance.

        Testing with the Diana 66 has to wait until next week when I get some darts as I have mislaid mine,



        • BB,

          Sorry tables do not work. A retry:

          Darts Bolts H&N 4.4 H steel
          speed 203 256 577 569 580
          grain 14.3 9.2 7.4 7.4 5.1
          ft-pnd 1.31 1.34 5.77 5.32 3.81

          Hope this looks OK,



  4. B.B, this is by far, my favorite AirGun test that you have done here.
    Your timing with reviewing this particular Benjamin multi pump air rifle is perfect for me since I have owned a pre-1957 Benjamin 317 for a couple of weeks and your tips have helped inspire me while I get my 317 into shape.
    After oiling the pump seals etc, it is shooting 5.4 grain Crosman penetrators a high as 695 fps and the heavier 8.5 grain penetrators hit around 600 fps!!!
    I am shooting indoors and my housemates prefer that I use lead-free ammo, and will take it outside soon to see how it shoots lead ammo.

    • Spinoza,

      Sounds like you have a nice 317. I would not shoot lead free pellets in the brass barrel of the 317. I think they are too hard and will wear the barrel. I have not tested my theory, I just think they will wear the barrel much faster than lead pellets. If you do shoot lead free I would lube them.

      If someone has been shooting lead free pellets in a brass barrel I would like to hear the long term results. It would probably take a few tins of pellets to wear the barrel.


      • Hi Don,
        The lead free ammo I am using is the sabot style with plastic skirts.
        I believe that the plastic skirt is what interacts with the inner barrel/rifling.
        It is probably a good idea to clean the barrel more often to avoid plastic residue building up.
        The other types of lead free pellets, like Crosman SSP hollow points would probably wear down the rifling like you said.
        I will update this comment in a month or two, after I clean the barrel.

  5. Hi B.B.,

    I was somewhat surprised to learn that PCP hand pumps are being sold without a desiccant kit attached, or at least a strong message about what happens to a PCP air gun when using the pump without one. No doubt this is a “caveat emptor” moment.
    No doubt, customers would best become educated. However, my understanding of Murphy’s Law isn’t the most quoted, but rather, “if anyone can do it wrong, someone will do it wrong”.

    Best to you, amigo,

    • Ken,

      There is a real question as to the effectiveness of a desiccant filter on the input of a hand pump or compressor for that matter. Does the air linger long enough in the desiccant to have any moisture removed?

      At one time one of the British companies, I believe Daystate, would void the warranty if the air rifle was filled by an hand pump.

      I have an Hill pump with a desiccant filter. I still get water in the trap.

  6. B.B.,

    A very nice set of testing. While I had the 880,… I tried numerous homemade dart-like projectiles. 12″ bamboo BBQ skewers. Same,… cut to various lengths. TIG welding rod. Even tried building the projectiles using arrow building theory,… length, center of gravity, balance, weights, fore and aft ratio, etc. Results did improve as I used it.

    In the end,.. it became QUITE obvious if the projectile did not land straight on,… the projectile would bend/break. Basically,.. if off,… the tail end would follow the angle. In other words,… the tail end would try to catch up with the front end after an abrupt stop. Distance to target, fpe of projectile and target material all came into play.

    The bolt and dart testing were a very nice diversion. Thank you.


  7. Chris,

    Exactly what I found when I analysed the numbers.

    Did you experiment also with darts? And what was the distance at which the darts became stabilized?

    After I read this I got some darts and tested them in an old Diana 60 at 10 meter. The Diana (with me, the Diana can do better) shot within 0,5 inch with pellets and around 3 inches for the darts with some entering sideways, so that supports BB’s notion that they are no good for accuracy.

    I have to wait until I get the proper darts for my darts enabled smootbored Diana 66. That one uses 5.5 mm darts and I am quite curious as to its performance now. I also will ask around at those shooting clubs which used these modified wapons. You just can have a competition when they fly al over the place like these 4.5 from my Diana 60 did.



    • August,

      No,… I did not buy any (proper) darts. Or bolts. I think that they might do quite well in something (very) low powered at short distance. My distance was 24′ and shot into a corrugated cardboard target holder/backer.

      It was a lot of fun and I learned a lot about arrow building theory. Perhaps some U.K. sites might be more conducive to dart shooting information?


  8. BB – You finally did it – I’ve been reading your blog for 15 years and have bought way too much stuff from Pyramyd Air, but have never posted until tonight. After your series on the 310, I had to jump in, and I thank you for the motivation!
    I bought my Benjamin 312 on Nov 1, 1961 when I was in the 9th grade. I still have the box, instruction sheet/parts list AND the receipt for $20.72, which included a whopping $.36 sales tax(!). I think list price was $25 then. What a wonderful air rifle! It probably took care of 500 grackles in my back yard before I left for college.
    Your observations are right on, but I’d like to offer a little more data on the bolt variations: according to my parts list, the 1-piece open-end bolt was used in the 310 AND the 312 since 1952, and also in the 317 from 1951 thru 6-1-55, when it switched to the current pin-style. Before 1951, all were two-piece bolts, but only the 310 had the open ended bolt..
    Another point: you mentioned the wobble-free trigger blade. What you said is true about the trigger spring wrapping around the triggers, but the real support comes from the fact that the trigger pin passes thru a bronze bearing that is pressed into the stamped trigger blade (the trigger spring surrounds that bearing, so you can’t see it without disassembling the trigger), providing great lateral stability and preventing the floppiness we see in too many products today. I kind of got away from air guns till about 2003 when I got a (Spanish) Beeman GS1000, and it escalated from there, including a Marauder and a TX200 Mk III.
    BB, you are clearly THE authority on air guns with your experience, honesty and insightful ness – plus you keep it interesting – where else are you going to read up on punt guns?
    Here’s a shot of my 312

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