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Airgun test and measurement equipment

by B.B. Pelletier

From the questions that have come in over the past six months, I believe many of you would like to start evaluating your airguns on a more precise basis, so today I’m going to look at some of the tools and test equipment I use to evaluate airguns.

Say the word airgun, and a chronograph is the first thing that leaps to many shooters’ minds. I have even read reader comments that suggest they like or dislike their airguns on the basis of what the chronograph tells them. But I don’t need to get into them here. I have written plenty of posts that deal with chronographs.

Here’s a good one for you:

Shooting with the Alpha Chrony

Tom Gaylord also wrote an article with a short video about the chronograph:

Who needs a chronograph?

The easiest way to measure the size of a shot group is with a dial caliper. Your measurement will seldom be exact, but the margin of error is so small that it’s insignificant. To measure a group, put the jaws of the caliper on the edge of the group at its widest point. This is where the inaccuracy comes in, because with many pellets it’s very difficult to determine exactly where the edge of the group really is. Take the measurement across the widest point and subtract one pellet’s diameter to find the width between the centers of the two pellets farthest apart. Sears sells calipers, and you can find them anywhere tools are sold. Pay around $20 for one made of stainless steel.

A cheap dial caliper like this makes the job of measuring group size a snap. Of course, it has hundreds of other uses.

I have a loupe and a handheld magnifying glass, plus I have a magnifying hood I often wear. Seeing things larger than life enables you to make judgements about such things as the condition of an O-ring, the sharpness of a muzzle crown, whether a discoloration is really a blemish or the start of rust and whether a solder joint is just scratched or cracked. I see them new in big electronics stores. Prices vary based on what you buy.

You can’t work on what you can’t see. Magnifiers are essential to the hobby airgunsmith and even to the general shooter.

Bathroom scale
Only the spring-operated scales work for this. Those with pressure sensors or balance beams don’t work as well. Use the scale to measure cocking effort by breaking the barrel past the detent, placing the muzzle of a gun in the center of the scale and pressing down on the butt of the gun until it cocks. To test sidelevers and underlevers, put the scale on a table so you can elevate the gun. Place the lever just like you would place the muzzle of the gun. This is a good garage sale item that should cost $1-3.

Alternative to the bathroom scale
I used to have a large barn, so I envy everyone who owns one today. One neat thing about a barn are the interior beams that things can be suspended from – including spring scales. Spring scales that go up to 50 pounds are ideal for measuring cocking force. They have a million other uses, but the one I remember was weighing hay bales to find out how dry they were. Find them at antique shops and farm sales and pay around $25-40 for a good one.

Trigger-pull scale
Twelve years ago, I bought one of these things because, if I was going to write about guns and airguns, I needed a way to measure trigger-pull. You can also use the one I have as a small spring scale for weighing things like air pistols. The electronic gauges are easier to use, but I guess I’ll just keep right on using my mechanical gauge. You’ll pay less than $30 for one like mine at Midway USA. They are essential when setting up a competition gun for a competition where the trigger-pull is mandated.

Trigger-pull gauge is one of the few purpose-built test items you need. It can also be used to weigh light things.

Balance beam scale
As rudely honest as these things are when it comes to weighing yourself, they are also absolutely true when it comes to the weight of an airgun. They are poor for measuring dynamic forces like cocking effort, but stellar for determining the total weight of something. These are pricey, selling used for $100 or so.

Postal scale
These are great for weighing smaller things like scopes, mounts, etc. They can handle more weight than a powder scale and are accurate enough for most work. Pay around $20 in an office equipment store.

Powder scale
These are very useful for weighing very small things like pellets and bullets. The electronic ones cost around $100. The mechanical ones go for $30-40.

Any of these things can be found on eBay for a lot less than I have quoted. If you look around your house, you probably already own several of them. You don’t need everything at once, but the most helpful ones are the dial calipers and the magnifiers.

40 thoughts on “Airgun test and measurement equipment”

  1. Hi B.B.,

    Could you tell me what constitutes a pellet that is too small for the bore of a spring piston gun and that may cause damage with air blow-by? I’m not sure at what point I should be concerned. For instance, the RWS Supermags I use always form a very tight fit on all my guns and I know they are fine, but when I switch to Hobbys or Gamo Match I find the pellet slips in quite easily without much pressure exerted. Even though I can’t visibly see any gaps between pellet and bore, I wonder if I should be concerned. Thanks.

  2. Seems to me that if you use a rod to push a pellet down a bore, you should get some idea if it’s too loose. Aren’t some breaches made a little oversize to facilitate pellet loading?

  3. BB –
    What type of grease should be used to lube the compression chamber of a Beeman P3/P17? The manual says to use joint grease, but at $21 for a small tube this stuff seems a bit pricey. Is there a commonly available substitute that is OK to use?

  4. Hello,

    I apologize for being off the topic, but I don’t know how else to ask this question.

    I’ve decided to order either an RWS 48 or 52. Is the 48 stock suitable for shooting with a scope? If so, is the 52 better suited for that purpose?

    Thank You! (and Thank You for a wonderful site)

  5. P17,

    I once topped off the master brake cylinder of my Ford Aerostar with the wrong specification brake fluid and had to have the brake system completely rebuilt. After that, I have tended to stick to manufacturer specifications unless I have a good reason not to.


  6. An off topic question.

    Do you know what speed range diabolo(ish) shaped pellets were actually designed to shoot?

    The design of the pelets, especially those with hollow skirts seem to be absolutely designed for sub-sonic flight, and to shoot straight wheter the rifle is barreled or not.

    It seems to me that I get better accuracy out of nice rifles that fire under 800 fps

    Which brings up my final question. It seems that the next step in airgun design (since there a huge fascination with super powerful air rifles) should be powerfull small bore airguns that fire solid pellets (bullets basically) much like the big bore guns do. Are any companies looking into this that you know of?

  7. Alfred,

    Welcome to the discussion!

    Diabolo pellets were originally designed to shoot in the 350-500 f.p.s. range. They continued to work well up to about 900 f.p.s., where they start fluttering in the transsonic region.

    Solid “pellets,” which are really bullets, have been made and used in modern times for about 15 years. The problem with them is that they are no longer stabilized by a hollow skirt and must therefore be spun faster (rifling twist) in order to stabilize at low pellet gun velocities.

    Lots of interest in them until the experimenter learns what’s been known for 200 years – that twist rate and bullet length/diameter are related. Then they find themselves trying to make an airgun do what a firearm already does.


  8. Alfred,

    You asked whether any companies I know of are looking into shooting bullets instead of pellets.

    Right now this issue is in the hands of some hucksters who don’t know the first thing about airguns. The make their “solid pellets” and then are amazed they nobody buys them because they are too hard to load. The few who are foolish enough to get suckered in to buying them then start touting fantastic claims for power and accuracy, but when anyone else tries to load these “pellets” they quickly discover that they don’t work well.

    So what you are actually asking is whether any company has ir is experimented with the correct twist rates and breech relief to enable solid pellets to le loaded and fired. To my knowledge, perhaps one man in Europe is doing just that. His .22 caliber rifle shoots copper-jacketed 50-grain slugs at 1,060 f.p.s. His rifles start at $2,000 and quickly go up over $8,000.


  9. and that is why my sheridan shoots straighter than my springer up to 30 yards, I suppose.

    My spring gun shoots well enough, but the 20 cal sheridan (inherited from my dad) doing way under that speed is a much more accurate rifle. (the real difference is probably under 1/8″ difference or so, but a guys gotta have his pride)

    Thanks for your response.

  10. WOW,

    Pretty pricey…. Then I have seen air rifles advertised that cost way more than Remington Model 700 (and a nice one at that) would cost.

    I imagine there are probably more hurdles to firing a bullet smallbore air rifle, than just rifling too. (Jump, I believe is the term, comes to mind)

    Thanks for the great info. I was indeed looking to see if a reputable company was looking seriously at this.

  11. B.B.

    Good blog on tools airgunners might need.

    On the Sears web site you can get a caliper for $7.99-$9.99, but the dial caliper is $29.99. Harbor Freight occasionally has a sale on their 6″, steel, digital caliper for about $13.

    Could a fisherman’s digital scale (like item# 94569 at Harbor Freight – http://www.harborfreight.com) be used for trigger pull and possibly cocking effort?

    Just a note on safety. I took the air tank for my converted RWS 850 to a local paintball store to get it filled. They used a SCUBA tank and did exactly as described in your post How to fill a precharged gun from a SCUBA tank. They connected the quick-disconnect, slowly opened the SCUBA valve until air started to flow and then opened it full blast! I wonder how many paintball accidents or problems come from fills?

    I printed off your post and plan to take it to them. Hopefully they will read it.

    .22 multi-shot

  12. I used a few drops of silicone oil (the RC car shock-absorber stuff) in my 2004 when I first got it (2 1/2 years ago), and it hasn’t complained since.

    BB – I’m real curious as to what sort of brake fluid you put in your Aerostar. Do you remember what it was?

  13. .22 multi-shot,

    I suppose a clever guy could rig a digital scale to test cocking effort. It woulde be easier to check trigger pull, but the one important thing you need is a means to record the highest effort, because when the trigger breaks, everything is lost. The RCBS gauge shown has that.


  14. B.B.,

    Inspired by your posts last summer on air rifle tuning, I decided to order some kits for my 2 Diana rifles. The model 46E I have definately needs some work. It should be producing about 12 to 13 ft lbs but is only averaging 10. I saw some pictures of a new 460 stripped down with light rust on the inside from a lack of factory lube. He commented it was spitting out a small amount of rust into the loading port. My 46 was doing the same thing.

    Anyhow, I just got the springs and various lubes today. These springs are huge. It certainly makes you realise the potential for bodily injury if an air rifle is taken apart without a spring compressor.

    I just got home from work a couple hours ago and the New Yankee Workshop was on PBS. As Norm would say, there is no more important tip than to wear your saftey glasses. Having a few extra pairs for your shooting companions is always handy too.


  15. Hi, my first time posting here.I like this blog very much.Dont know if this is the right place to ask you if you could shed some light on how the mechanical/recoiless actions of the British Park Rh 93 series air rifles works.
    I know they use two opposing pistons but with different weights and spring power.
    I have one and a pellet stood on the gun stays there after the shot.Their accuracy is outstanding.

  16. David,

    It’s been so long since I heard anything about the Park rifle. I believe there were two models and the opposed pistons were pulled apart with a miniature bicycle chain.

    It has a Lothar Walther bbarrel and is very smooth-shooting, if a little difficult to cock.

    That’s about all I know.


  17. bb,

    I had never heard of park airguns before this day, That means most airgun fans havent. It also means theres a couple of other manufacturers i havent heard of. I just recently heard of twinmaster. Food for thought.


  18. Sumo,

    Like I said, I don’t really have enough information to report on the Parks. And what about the Parker Hale Phoenix? I can’t do that one, either.

    I do try to run in guns I have tested or have information on when I can. Like right now I’m thinking of reporting on the Mag Air 1180, a 118-caliber beast that makes even today’s big bore pale in comparoson.


  19. bb,

    i was not asking a question, i was just saying i probibly have not heard of many airguns if i havent heard of park.

    Heres a question,
    Out of the rws 460, gamo hunter extreme, webbly patriot, what would you say is the most powerful if they are all using the same pellet. I think a bunch of people want to know. Are there any small bore spring guns out there that are more powerful than any of them?

    In a nut shell, what is the most powerful spring small bore airgun.


  20. Sorry if this was answered before somewhere, but is the Walther LG300 Dominator no longer in stock on pyramidair? I searched the site but found nothing. Was it discontinued?

    Secondly, are you guys planning on stocking up any Walther 1250’s? Umarex says they are basically a lot like the LG300’s but instead have 8-shot clips.

  21. Sumo,

    Since the RWS Diana 460 isn’t available for testing, it’s difficult to answer your question.

    The funny thing is, the Patriot isn’t that powerful in .177. The one I tested couldn’t drive CP 7.9s to 1100 f.p.s. But in .25, it shines.

    I would expect the reverse from the Gamo, though I haven’t tested it. If it really can shoot a .177 to 1400 (I believe 1600 isn’t possible without tricks) then it’s probably not as good in .25, though it isn’t made in that caliber. The guns seems to be optimized to one caliber, or possibly two, but not all four.


  22. BB,
    I only like 22 caliber airguns. It realy limits my options on guns. I only buy pre-charged guns so i guess it doesent matter. The 460 may be good enough to change my mind. The guns i have already are hard to beat. I will get another career before i get another rws. I had an rws 54 until it broke.

    1250 guy,
    the 1250 does not look like much of a replacement for the LG3000. They look like they have differant puroses.


  23. Question about measuring a rifle’s capabilities. Lets say I place my rifle in a stock, barrel perfectly horizontel pointed downrange, fully loaded. Barrel is, say, 4 feet above the level ground. I fire, then measure the DISTANCE to the pellet’s impact site (on the level ground). Crunching the numbers with the proper equation for the amount of time calculated for the pellet to drop the 4 feet, would this give me an “average” pellet velocity for the entire downrange flight without divvy-ing up the dough for a ballistics chronometer?

  24. BB,

    Two questions for you and one for all.

    1) Quote : To my knowledge, perhaps one man in Europe is doing just that. His .22 caliber rifle shoots copper-jacketed 50-grain slugs at 1,060 f.p.s : Unquote

    Is that the Beaumont rifle you are refering to ? If so, would it be possible to do a post on it ? Am very keen to know about it.

    2) Any material/post on AirMag 1180 ? Never heard of that one.

    All Readers,

    Any one can translate this article by any chance ? Go to : http://www.qsa-trading.nl/

    Click on Airguns, and then on Beaumont. There are two links that read as : Review of the Beaumont® Tactical by VISIER Magazine Part 1 / Part 2

  25. MasjorKonig,

    Yes, I think I was talking about the Beaumont. I will be pretty difficult to test one as they are handmade for customers. I have seen them and they are gorgeous. The one I saw was an $8,500 rifle.

    Yes, I will do a report on the MagAir 1180. I also tested one of them and it is an awesome airgun (not a rifle).


  26. Great blog on tools of the hobby. Have one suggestion for pistol shooters.

    When you change the wiper blades on your car save the steel stiffening bars from the rubber. The metal is smooth, rust resistant, and stiff. This makes it great for use as a push rod for short barrels. It will fit either 177 or 22cal.

    Bend one end to a 90-degree a 1/2 inch or less from the end. Then use the full length to push out stuck pellets and the short bent end to seat pellets when loading.

    They also make a great disposable stirring stick for epoxy and hundreds of other things.

    It is free and your saving it from the land fill.

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