Shooting airguns at altitude

by B.B. Pelletier

A lot of you asked for this report but Jay was the first. As we drove from Texas to Las Vegas and the SHOT Show, we passed through several communities higher than 5,000 feet, and my appreciation for how widespread this problem is certainly increased. We think of Denver as the mile-high city, but there are plenty of smaller cities that are even higher, so knowing something about how airguns perform at altitude is important.

When we published The Airgun Letter, one of our readers, airgun dealer Howard Montgomery, did a test of spring guns, CO2 and multi-pump pneumatics shot at elevations ranging from sea level to 8,500 feet. He based his tests on another earlier study done years before by airgunner Ron Balbi.

Howard used the following guns:

RWS Diana 36 in good shape (.177)
Webley Hurricane pistol in good shape (.177)
Crosman 1377 in good shape (.177)
Crosman Mark II in good shape (.177)

Both an Oehler 35P chronograph and 2 Chrony F1 chronographs were used. The light pellets were RWS Hobbys and the heavies were Crosman 10.5-grain Premiers.

Howard also provided a test from Ron Balbi done years earlier and archived by airgunner Steve Gibbons. The guns used were:

FWB 124 (.177)
RWS 45 (.177)
Beeman R1 (.22)

So, the trends operate as shown. If you do your own test today, you’ll get different results, but the relationships will be similar. Remember, temperatures below 50 degrees F will affect CO2 guns and temps below 20 degrees F will start to affect spring guns. Also, note that as the air thins at altitude, a gas gun can go faster. PCPs were not tested, but they should improve at altitude.

26 Responses to “Shooting airguns at altitude”

  • Don Says:

    BB,
    Although the report doesn’t say so, I have to assume that the 1377 was pumped the same number of times at each altitude. This only makes sense for comparing the results at different altitudes. However, since the reduced power at altitude is the result of thinner air, wouldn’t it be possible to pump the multi-pumper more times without exceeding its design limitations for pressure, and achieve the power available at sea level?
    Don

  • B.B. Pelletier Says:

    Don,

    Yes, the pistol was pumped the same number of times at each altitude. And I have always thought it would be possible to pump an extra time of two at altitude to compensate for the thinner air. A chronograph would tell the story.

    B.B.

  • B.B. Pelletier Says:

    Omission!

    Everyone, I read the posting again this morning and realized that I failed to include the Gamo 2000 in the listing of airguns used in Howard Montgomery’s test. It was a breakbarrel spring rifle in .177 caliber that had a muzzle velocity of 820 f.p.s., according to the Blue Book. The rifle used in this test was new, and obviously more powerful than that.

    Writing blogs from an RV while covering the SHOT Show is less than ideal. Things should settle down starting Wednesday of next week.

    B.B.

  • Anonymous Says:

    Living in Denver, I noticed how poorly my high power spring guns performed. So, about 10 years ago I tested high and low power spring guns, an FWB 127 with a top of the line Beeman tune and a Chinese side lever AK 47 copy. My altitude variation was between 1500 feet at Audubon Iowa and 12000 feet above sea level at the summit of Cottonwood pass. The low power gun lost about 10% of its power at the summit, the FWB about 20%.

  • jim Says:

    BB,
    What’s the deal with the HW45 being discontinued?

  • B.B. Pelletier Says:

    Jim,

    I announced a couple of weeks ago that HW orders were not being filled for a year, so Pyramyd Air has decided to drop the line. They will still stock Beeman HW guns, so the P1 and P11 are still available. Once the HW guns are sold, they will not be replenished.

    If Pyramyd Air can get a reliable supply of HW airguns in the future, they will carry the brand again.

    The HW 45 is still being made – you’ll just have to buy it somewhere else.

    B.B.

  • Bar 1 Says:

    Hi BB,

    Hooray, just the data I was looking for! Unfortunately it was posted too late to do me much good….I finally had to buy a chrony last week to find out whether my (second) RWS 46 would have enough power to use on pests out to 40 yds at 5700 ft. In my opinion, it does not, and I am now thinking to trade up to the 460 Mag. Here are my results:

    RWS 46.22, barrel cleaned w/ JB, then 100 shots before chrony. 5700 ft, 60 degrees (inside), one foot from muzzle

    Crosman Premiers 14.3 grains:
    519.3
    521.6
    518.6
    524.1
    519.1 Avg 523.9
    534.2 Hi 534.2
    527.5 Low 517.4
    528.4 Spread 16.8
    517.4
    528.8

    RWS Hobby’s 11.9 grains:

    598.5
    597.5
    594.4
    594.1
    597.8 Avg 596.8
    604.9 Hi 604.9
    593.5 Low 592.3
    598.3 Spread 12.6
    596.8
    593.3

    Plugging these numbers into a ballistic program, at 40 yds the premiers will be down to below 5 f/lbs energy, with about a 6 inch drop. I won’t chance shots at any game with those numbers. Wish I had known this back in December.

    Doing the math for your numbers, I get for the RWS36:
    4500ft 10.5% loss
    6500ft 15.6% loss

    Since I don’t know how my 46 will do at sea level, all I can do is work it backwards, and I get:

    Premiers= 579
    Hobbies = 689

    Two different tuners say the 46.22 is only a 700 fps gun, so these are in the ballpark.

    Oh Well, live and learn in the complex world of airgunning.

    Jay

  • Bar 1 Says:

    Whoops, forgot to extrapolate from 5500 feet instead of 6500.

    sea level extrapolation for my 46 should be:
    Premiers = 589
    Hobbies = 672

    A little low to my thinking, but doesn’t indicate anything wrong with the gun.

    Jay

  • Anonymous Says:

    This may be a question already answered, and it’s been quite a while, but are you going to finish the SS1000-H review, scrap it, or try to review another one? At last glance, I saw that you said that you would try to decide whether or not to continue the review, but you never gave a response. If it’s of consequence to your schedule, then I’ll leave it alone and decide on on my own if it’s worth trying.

    14 in Fla

  • Kyle Says:

    Hey BB

    Has anyone ever put a chrony out at say 35 yards and tested velocities of various pellets and compared that to muzzle velocity? I know there are ballistic programs that can tell you these numbers but I can’t imagine that they’re 100% accurate. I would like to try this myself but I don’t think I’m really all that dedicated to airgunning to spend 100 bucks on a chrony of my own.

    Thanks, Kyle.

  • Jonathan Says:

    Hola
    A while ago you asked me to bug you about posting a review on the Crosman 1088 in two weeks, so I’m bugging you about it.

    Bug Bug Bug

    On another note, I’m planning to get the HFC M199 Full/Semi Auto as soon as I get enough money to justify buying it. From everything I’ve read, the HFC M190 is a great gun, and I’m assuming that the M199 is the same gun in all respects except for the grip.

  • B.B. Pelletier Says:

    Bar 1,

    Sorry the data came too late for you, but now you know. And your own numbers expand our little database

    B.B.

  • B.B. Pelletier Says:

    14 in Fla,

    I will certainly complete the test of the 1000H. I spoke to Don Walker, Beeman’s repair manager, at the SHOT Show. He told me one thing that may be wrong with my rifle that I can fix in an instant. But if it isn’t that, I’m going to ship him the rifle and he’ll tell me what went wrong, plus repair the gun so I can continue.

    I will keep you informed of what happens, but if I forget, drop me another line. I want to put this info into a regular blog, because many other readers are interested it it, as well.

    B.B.

  • B.B. Pelletier Says:

    Kyle,

    What you suggest has been done, and, no, the programs are not completely accurate. They are useful, for the most part, however, and they save a bunch of time.

    To test what you suggest requires two calibrated and matched chronographs, or else you’ll wind up with a good guess. No two chronographs read exactly alike.

    B.B.

  • B.B. Pelletier Says:

    Jonathan,

    Too soon on the reminder. After next Tuesday, please.

    I’ve heard good things about the fiull-auto pistol from the Pyramyd Air techs. I’ve never shot one myself.

    B.B.

  • Shooter Says:

    Hi Kyle and BB,

    Just wanted to add to what BB said about the chronograph at a distance. In my case, using a ballistics program would probably save me from buying a new chrony for each test after putting holes in it at 35 yards… ;-)

    /Shooter

  • Shooter Says:

    BB,

    Looks like gas guns, pumps and PCP’s are for us hypoxic folks.

    /Shooter

  • Kyle Says:

    /Shooter

    haha good point, maybe we can back it down to 25 yards haha

    Kyle

  • Anonymous Says:

    Thanks to B.B. and Sumo for yesterday’s enlightening comments about the alignment of air pressure in single shot guns. That will motivate me for each crank of the B30 when my impulse is to blaze away….

    Matt61

  • Anonymous Says:

    Tom would the temps affect a gas spring the same as a conventional one? When I’m out in the summer and it’s close to 100 degrees, I could swear my gun has more power. I would assume (you know what they say)heat would cause a slight increase in the pressure of the gas spring. From SavageSam.

  • B.B. Pelletier Says:

    SavageSam,

    A gas spring has less lube on the piston, which is the part that moves. So, when the rifle fires, there is less to slow it down. I tested a gas spring down to zero degrees, and although it lost 20-30 f.p.s. (probably from the loss of gas pressure that you suspect) it was considerably better (faster) than a coiled steel mainspring.

    But a PCP beat them both. It lost almost no velocity at all.

    B.B.

  • Anonymous Says:

    hey, what getting a dragon slayer
    .50, I live in the Florida woods and I’m 15, I wan a big gun to hunt.

  • Wacky Wayne Says:

    Thanks again for great info;

    We are here in S. Oregon at 2,700 ft. and so I guess that our Avenger 1100s (Mendoza 600s right?) spring rifles are about 8% under powered. But they still seem very fast (not breaking the sound barrier anymore after break in), but, right on target, and bury the .177 pellets 3/4″ into hard dry wood at 60′ indoors 70 degrees.

    We don’t have testing equip. yet so the board test is all we have, but the board is harder than a rat or starling (which is what we shoot other that targets)
    So, we will take some of the same boards shot at 2,700 ft up to 5,700 Mt. Ashland, (20 miles away) and see the difference. (Report later)
    Meanwhile, it seems we wait till march with even more excitement for the “Benjamin duel fuel PCP”

    Also, the mark II was the only gun to have higher fps at the higher elev. it is not offered anymore on PA so what kind is it?

    Thanks, Wacky Wayne, Ashland, Or.

  • B.B. Pelletier Says:

    Wacky Wayne,

    The Crosman Mark II is a single-shot CO2 target pistol. I blogged the Mark I. It is a classic.

    http://www.pyramydair.com/blog/2005/06/crosman-mark-i-target-pist_111919768362235628.html

    B.B.

  • Anonymous Says:

    BB,
    I understand I can expect a power
    decrease of about 15% when shooting around my new home in Ft. Collins, CO (5000ft above sea level). I plink and target shoot at about 25yrds. How will my TX200 MKIII perform at 85% power? Will
    it still be enjoyable to shoot at 25yrds? I don’t have a lower powered gun on hand to compare the TX200 to.

    Thanks,
    David

  • B.B. Pelletier Says:

    David,

    5000 feet should be no problem. When you get above 6500, some guns start sounding funny and their owners feel they are causing damage. I have never studied the problem, so I don’t know if that’s the case, but you are well below that elevation, so I’d say you are safe.

    B.B.

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