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Ammo Sterling HR-81 .177 underlever air rifle: Part 3

Sterling HR-81 .177 underlever air rifle: Part 3

by B.B. Pelletier

Part 1
Part 2

The Sterling by Benjamin Sheridan is an air rifle not many have seen or even heard about.

Say hello to my little friend! We last saw this Sterling 11 months ago and discovered during testing that the velocity was very unstable. Variations of 61 to 147 f.p.s. were found in the 10-shot strings, even though the rifle had been recently tuned by reader Jim Grossman (Jim in PGH). Clearly, something seemed to be wrong. I stopped the test right there because I didn’t want to damage the mechanism, and I set it aside for later when I could I eventually look inside.

Well, our No. 1 tuner and all-around good guy — blog reader Vince — stepped forward and offered to have a look at it for me. He told me he’d worked on another Sterling, and I was relieved because I didn’t have to learn the complexities of yet another odd spring-gun mechanism. This one is odd because, in addition to the underlever that cocks the mainspring, the gun also has a bolt-action that opens the breech for loading a pellet. It’s quirky and unlike just about any other airgun you’ve seen.

Vince was as good as his word, and the gun is now back with me. I’ll let him tell you what he found inside and what he did to the gun at his convenience. I just want to get back to the original test.

An odd duck
The Sterling is an odd spring-piston mechanism, to say the least. As I said, it cocks via an underlever but is loaded in a trough on top of the action by retracting a spring-loaded bolt; so when the handle is lifted, it jumps back out of the way and exposes the trough for loading. The trough is sculpted to make it easy to roll in a pellet, so loading is a snap.

The Sterling bolt is spring-loaded to jump back and open the scalloped trough, which easily accepts a pellet.

The rifle was made both in the UK and in Racine, Wisconsin, by Benjamin-Sheridan before Crosman bought them. It’s a large, solid rifle that looks and feels like a magnum, though the performance is strictly under 12 foot-pounds. One attractive feature of at least the American-made rifles is the barrel from Lothar Walther. It should be fairly accurate.

The UK Sterling suffered from a lot of quality issues, the greatest of which were a very buzzy action, a trigger that tended to fall apart during use, sights that fell off and a rear sight that is apparently of very low quality. I can’t comment on the sights; because when I got the rifle, all that remained was the hollow shell of the globe front sight. Benjamin Sheridan was frustrated by front sights falling off, so they engineered a solid front piece that includes the globe for the sight within the same piece that serves as the catch for the underlever.

The front sight globe is made as a unit with the underlever catch.

In the first part, I complained that the single-stage trigger was a little creepy. Well, either I was being overly critical or Vince did something. Although it still breaks at 2 lbs., 8 ozs., this trigger is now pretty crisp! I’ll learn more during the accuracy test, because that’s when I become intimate with the trigger. For now, I’ll just say that it’s a good one.

Cocking effort
The rifle cocks with 26 lbs. of effort, though it feels a little lighter. That’s probably because most of the effort over 20 lbs. occurs in the last 20 degrees of lever arc. There’s no anti-beartrap device. The bolt-action design keeps your fingers without one, so you can uncock the rifle at any time.

When we last looked at the American-made (Benjamin) Sterling, I shot it with three different pellets to obtain the velocity/power rating, so that’s where I’ll begin today.

Falcon pellets
First, I tried the 7.3-grain Air Arms Falcon pellet. In the test done before this work, the pellet averaged 626 f.p.s., but the velocity ranged over 147 f.p.s. The average velocity equates to a muzzle energy of 6.38 foot-pounds.

With Vince’s work, the Falcon pellet now averages 754 f.p.s. — a 107 foot-second gain. The spread was reduced to 23 f.p.s., from a low of 738 to a high of 761 f.p.s. That’s quite stable — especially in light of the former test. The current muzzle energy is 9.22 foot-pounds.

JSB Exact 8.4-grain dome
The next pellet tried was the 8.4-grain JSB Exact dome. In the earlier test, this one averaged 597 f.p.s. with a 61 f.p.s. spread from 564 to 625 f.p.s. The muzzle energy was 6.65 foot-pounds.

In the current state, this pellet averages 704 f.p.s. with a 19 foot-second spread from 696 to 715 f.p.s. That is another gain of 107 f.p.s. And the muzzle energy increased to 9.25 foot-pounds.

You don’t normally see a heavier pellet making more energy than a lighter one in a spring-piston powerplant. It’s indicative of a heavy piston, which is perhaps the reason the rifle has a pronounced froward jump upon firing.

Is it hard to believe that heavier pellets typically produce less energy than lighter pellets in spring-piston guns? While this is not 100% the case, it’s probably the case 9 times out of 10. Spring-piston guns do not transfer their potential energy very well, and therefore lighter pellets that offer less resistance are usually slightly more efficient. In pneumatic and CO2 guns, the reverse is true: heavier pellets produce more energy most of the time.

Crosman Premier 7.9-grain lites
The last pellet I tested was the 7.9-grain Crosman Premier lite. In the first test, these averaged 580 f.p.s. with a 144 foot-second spread from 467 to 611 f.p.s. I tried flaring the skirts of these pellets to get a better seal in the bore, but the average velocity increased to only 584 f.p.s., while the total variation increased to 152 f.p.s.

In this test, Premier lites averaged 705 f.p.s., and the spread went from 698 to 712 f.p.s. — a 14 foot-second spread that was the tightest of the entire test. The gun now shoots 119 f.p.s. faster than before. The average muzzle energy is 8.72 foot-pounds — the lowest of the three pellets tested.

The evidence is overwhelming that Vince made some important changes to the Sterling’s performance. I’m sure his account of what was done will be of great interest.

Bottom line
My research into the history of this fascinating airgun revealed that very few airgunners who know about the Sterling are neutral about it. They either love it or hate it. Blog reader Robert from Arcade also expressed an interest in the design, as did a number of other readers, I believe. That’s why this test is so important. It’s been more than two decades since I read about this air rifle in the British press, and I have always wondered what the truth is. Now we can all find out together.

29 thoughts on “Sterling HR-81 .177 underlever air rifle: Part 3”

  1. The UK/Sterling original versions of the gun (two models HR 81 and 83) had a most inconvenient rear sight mounted atop the breech block. The Benjamin reworking got rid of this and replaced it with a Williams peep sight for the HR83, and a movable version of the original sight for the HR81, positioned on the dovetails. The gun pictured above is missing both.

  2. So what did you use B.B.? Or are you saving that for the accuracy report?

    I do not know what the internal parts are like, but all the photos seem to show solid machined parts, not a bunch of cheap stampings. I think this rifle has the potential to be very interesting (for a springer).

  3. I have always preferred quirky underlever air rifles and even use a Diana 46 in .22 for hunting squirrels. Many criticize that one because of the flip up tap which robs it of power because of it’s long transfer port and problematic sealing of that type of breech. Other folks distrust the other under levers especially the Chinese ones, because of the danger of placing their fingers in the loading area, although proper loading technique will alleviate that danger. It always seemed to me that the Sterling had both of these problems licked with their design. It is too bad Crosman didn’t keep the gun in production as it was better than the stuff they did come out with in their earlier spring guns. It had good sights, a great barrel, was safe and easy to load, and made power similar to what the Benji pumpers made with only one stroke of the lever. Too bad that the 1000fps break barrels killed it. Wish I had had the coin to purchase one back in the day. Thank-you for reviewing this one, and I’m also looking forward to Vince’s review of what he did to it. Did you get Williams sights for it?

    • Robert,

      No, I don’t have the right front sight insert for it yet. Or at least not the retaining ring. I know I could fudge that, but I’d rather not. I do have Williams sights, but I’m going to test this one with a scope.

      My thinking is that a Leapers long eye relief scope in 1.5-4 power would be ideal, but I don’t know that I have one to spare. I have so many firearms and airguns under test for major articles that my scope corral is as low as it’s ever been.

      If I can find the right 30mm BKL mount I might just mount that wonderful Hawke scope I am doing an extended test on. 😉


      • B.B.,

        Be nice to have a open sight/peep sight option for that svelte gun.

        The bluebook seems to indicate that the HR 81 and HR 83 are identical models with the exception of the rear sight. As Oliver said the difference appears to be the addition of a williams peep on the HR 83. I know you have boxes of williams peep sights.

        If you care and when you have time let me know if any of your other inserts fit the front globe on the Sterling and whether any of your retaining rings in the front globes on other rifles fit the Sterling. Since I have many spare inserts and retaining rings I might be able to help make that Sterling whole.


  4. B.B.

    A couple questions about this rifle…

    What kind of relationship is there between land and groove width? (wide land narrow groove, narrow land wide groove, about equal width)

    How do the pellets seat? (not seated, head in bore, head and skirt both in bore)

    I am attempting to make some sense of what I see that does not follow “the rules”. I have some theories, but am unable to “see” exactly what is going on.


    • twotalon,

      I will try to answer your questions in the next installment, which will be after the SHOT Show next week.

      The pellets are seated by the bolt nose, and they have to pass the air transfer port. So it’s safe to assume they are pushed into the rifling all the way. Wouldn’t make sense to do it any other way.


  5. I’m with Robert on this one! I like underlevers. Maybe if BB sweet talks them, Crosman will revive this model. I enjoy my underlevers, but it would be nice to have one that’s made in the USA.


    • /Dave,

      I doubt anyone will ever make this airgun again. As well-made as it is, this would be a $500-600 air rifle.

      It’s sad that it’s just too nice to be made today, but that’s probably why Crosman decided to drop it when they took over. After the initial 300 sold to enthusiasts, they would sell maybe 50 a year. They need numbers of a thousand or more.


  6. It’s very difficult for me to ask Vince for a blog on what he actually found and fixed when he went inside the Sterling. I’m sure Vince has written more guests blogs than anyone. Very unselfish guy that one.

    I’m guessing one of the o’rings.

    Nonetheless, it always brings a smile to my face when a vintage gun is saved and is now shooting to spec (according to the bluebook). The apparent improvement to the trigger is a big bonus.

    Well done Vince.


    • Kevin,

      I feel the same way about asking him for things. I know what he found, or at least some of it, but I want to let him tell the story, and there’s no schedule. He can do it when he’s ready. Like you, Vince is another of our resources that I would hate to burn out.


      • OK, I’ll ask him here…

        Hey, Vince! You don’t know me, but…… “Would you do a blog for us on fixing BB’s Sterling?” We would really appreciate seeing the inner workings of this gun! 🙂

        /Dave (and three rest of us)

          • That’s great news! I’ll look forward to it!

            If you can’t talk Crosman into ressurecting this model, and since I don’t own a Blue Book (I know you’re gonna hate what’s coming, sorry, but…..), “How much would a model like this be, that maybe needs a reseal like yours and perhaps about 80-85% or there-abouts on the finishes?” Assuming, a guy could find one… Is it a big collector’s item with premium pricing, or maybe just an old shooter? I’d be after a decent, maybe worn shooter… Just wondering about a ballpark figure. You said it would be a $500-600 new if it were made… Would it be the same, more or less for a original, or way more?

            Can you tell I kind of like the looks of this one?


  7. Yeah, I’m planning to do a write-up, but I can’t guarrantee when that’ll get done. Sorry ’bout that.

    I appreciate the kudos, but prudence dictates that they be withheld until the gun has some more mileage under its belt. WHY I say that will become obvious.

    Now – as to what was really wrong with the rifle? I’ll drop a hint:

    Rubber Baby Buggy Bumpers.

  8. OT…woohoo…this past Saturday I wrote my PAL (possession and acquisition license) up here in Canada.
    50 question written test and a practical test with three firearms (bolt, lever and pump shotgun).
    Passed (of course 😉 )
    So in about 6 weeks my paperwork will come in the mail…meaning the Savage .22WMR I purchased before Christmas (paid for and stored at a friends home who is legal) can be transferred to me).
    But just as important…I emailed my dealer and asked them to order the HW97 I’ve been drooling over.
    Ooooh…can’t wait for both of them.

  9. Off Topic

    Thought I just post a quick note. I had a broken spring in my old RWS 36. I bought a drop in replacement spring from Vortek and thanks to BB’s hint on putting the rear pin in first the gun easily went together. (Thanks again!) After a few dozen shots I chrono’d the gun. I had picked up over a 100 fps from my last spring. However, even though the velocities were very consistent the accuracy was horrid.

    I had just bought some Daisy pellets and my gun didn’t like them at all. I finally picked up some Crosman Premiers, which worked well before, I am now again able to hit coke size cans at 50 yards fairly consistently. This is the most I feel I can hope for when shooting while standing and with the standard iron siights.

    I have to say that changing the spring in my gun wasn’t anywhere as hard as I had read and with a little care, very doable. One thing thought, in one article I read where someone was able to rerplace a spring in his RWS 34 without a spring press. All I can say is if true I’d hate to meet that guy in a dark alley!

    • Yes, you wouldn’t want to meet me in a dark alley. Or anywhere else, for that matter, if you have any standards when it comes to your acquaintances…

      Seriously, though, it’s really quite easy. And the ’34 isn’t that bad. I’ve done Diana 48’s, Powerline 1000’s, AR1000’s, and (in a fit of absolute insanity) an MP513. I’m still amazed that I EVER got THAT one back together.

      I’m average size (well, vertically, anyway) and strength. There’s no great trick to it, really.

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