Barrel droop

by B.B. Pelletier

Barrel droop is a phrase that I believe was coined by Tim McMurray to describe the airgun barrel that points downward in relation to the top of the receiver (where the scope is mounted). It’s been around as long as there have been airguns, but it was the scope sight that made it visible.

What is barrel droop?
From the name, you might suspect that we’re talking about a barrel that somehow bends downward, but that’s not the case. Barrel droop is actually a straight barrel that’s been mounted in the receiver so that its axis points downward. There are bent barrels that point down, of course, but that’s not what we mean by barrel droop.

Why does the barrel point down?
Good question. Why does the barrel of your Winchester model 70 point down? You say you think it doesn’t? You’re probably right. Yours probably points up! The point I’m trying to make is that almost no rifle barrel points exactly straight ahead in relation to the rest of the receiver and, more specifically, to the machined mounting pads where the scope bases go. Airgun barrels are the worst offenders, by far.

Come with me!
Take a close look at the Webley Patriot. If you’ve followed this blog, you know I think a lot of the Patriot, but look where the front sight is mounted. It’s on the end of the barrel, isn’t it? Where’s the rear sight?. It’s on the OTHER END OF THE BARREL! You may not be able to discern that in the photos, but both sights are mounted on the barrel. This is a breakbarrel rifle. That means the barrel swings down through an arc when the gun is cocked. The sights maintain a perfect relationship with each other because they both move. So, naturally, the gun shoots to where the sights are adjusted. If you mount a scope on the Patriot, where does it go? On the back of the receiver – the part that doesn’t move when the barrel is cocked. So, a scope will be sensitive to where the barrel points, while the open sights just ride along with it.

But it’s not that simple
Let’s now look at an Diana RWS model 52. Because it cocks with a sidelever, the barrel doesn’t move on this model. Plus, the rear sight is mounted on the receiver tube – not on the barrel. Know what? The RWS 48 and 52 have reputations for being droopers! Yes, they do. So, that fixed barrel that you thought would take care of everything didn’t do all you had hoped, did it? Don’t fret, though. The Weatherby Mark V that cost you $1,200 last year doesn’t point straight ahead, either. You took care of that one when you sighted in your scope, and you’ll do the same for your air rifles, no matter what kind they are.

Here’s what’s happening
First, the bore of your rifle does not run straight through the center of the barrel unless you paid a lot of money for it to be made that way. Second, all screw threads have room for fitting – called “tolerances.” They cannot be perfectly machined and still go together, so if your barrel is screwed into your receiver, it isn’t straight. If it is pressed in, as are most airgun barrels, it isn’t straight either because the hole in the receiver isn’t straight, which is my next point.

Third, the hole in a rifle receiver is not bored straight in relation to anything. What would it be straight WITH? Fourth, the grooves or mounting points on top of the rifle receiver are not straight with the receiver, except by accident. In short, in the world of manufacturing, everything is off by just a little. Usually, the amount they are off is so small that you don’t notice it; and it’s cancelled when you sight in. Sometimes, everything works together against you, and the rifle has a REAL problem!

The fact is that most of today’s spring-piston air rifles point down to some extent. If the angle is small, you can correct it with the scope adjustments. If it’s large, you need an adjustable scope mount. Tim McMurray sold a “Drooper” scope mount that corrects downward slant. For really bad rifles, there was the “Sooper Drooper.” He had the rings bored out on an angle so they held the scope on a downward slant. It worked, but adjustable mounts came along and eventually proved even better. We’ll look at them tomorrow!

27 Responses to “Barrel droop”

  • Anonymous Says:

    BB,

    What does Webley Gun Blue “First Class” do in an air rifle.

    Thanks

    CF-X guy

  • B.B. Pelletier Says:

    CF-X guy,

    Webley First Class Gun Blue does just what the description says – it restores the blue color to scratched areas on the metal of guns. All “cold” blues do the same thing. They are a chemical solution that colors steel on contact without heat. They also require a lot of technique to do a good job, so don’t start a project unless you read up on applying cold blues.

    B.B.

  • turtle Says:

    Looking forward to your suggestions on adjustable mounts. I have a FX Revolution coming and am looking for an adjustable that will clear the height of the Magazine that sits on top. Any info the clearances will help a ton. thanx.

  • B.B. Pelletier Says:

    turtle,

    It’s all there on the website. The high mounts have the most clearance.

    There is NO table of clearance heights of mounts compared to individual guns. Too much info!

    B.B.

  • shootin’ blanks Says:

    i recently went out to shoot an old sheridan blue streak and had a problem, it seemed that after a few shots the gun would shoot slightly to the left i figured that it was because the heat from the pump mechanism was warping the barrel am i right in thinking this and if so is this performance typical of a sheridan/benjamin rifle?

  • Anonymous Says:

    Hi B.B.,

    I have a RWS48 and contacted RWS about correctly mounting a scope on it. After speaking with their gunsmith, all RWS airguns are designed with barrel droop. It is not by reputation but fact! After adjusting my RWS C mount as suggested by their gunsmith, my RWS shoots very accurately. Great article by the way.

  • cold shooter Says:

    B.B
    thanks for the insights into the imperfections of manufacturing. would you suggest a few pellet brands that are over size in .17 and .22 calibers?
    thanks again.

  • B.B. Pelletier Says:

    cold shooter,

    In .22 I always used Eley Wasps. At 5.6mm, they are really oversized! But they aren’t available here in the U.S. I guess RWS Superpoints are a good substitute. They aren’t oversized butbthey have the thinnest skirts I know of and they expand when fired.

    I don’t know a good oversized .177. maybe a reader can help? I do like RWS Hobbys. They aren’t oversized but they are on the large side of normal.

    B.B.

  • Anonymous Says:

    Great article! Everything I wanted to know about barrel droop and then some. I was a little concerned about the barrel droop comment on RWS guns I saw on the web when I purchased my RWS 34. Thanks again for taking the time to address my question.

    On another topic: I had decided to play with the iron sights on my RWS 34 before mounting a scope so I was playing with it yesterday. I was taught that once you align the sights, you should aim just below the target (bullseye in this case). I read in your article on sighting an airgun with open sights that you should be about 1 inch below the target at 10 yards. However at 10 yards I had the rear sight about bottomed out and was not able to get any lower than the target itself. Am I aiming too high? Other problems?

    jw

  • B.B. Pelletier Says:

    jw,

    Move back to 20 yards and try to hit the same target. Then you tell me.

    B.B.

  • Adrian Hunter Says:

    How can i increase the power of my airgun,that is a Gamo Maxima ’22 cal.?What type of lubricant should I use for my pellets to increase their velocity if I want to avoid any dieseling in the barrel that could destroy the internals of my air rifle?Is there any type of this kind of lubricant that doesn’t initiate combustion in the barrel?

  • B.B. Pelletier Says:

    Adrian,

    I didn’t know what a Gamo Maxima was until I looked at the Pyramyd Air website. Boy, that’s a BSA Supersport if ever I saw one!

    As far as power goes, you either need to increase the stroke or the bore and the stroke is the easier of the two. I’d suggest trying to add a half-inch if you can.

    Lubricants all burn, so your gun is burning lube right now. You need to read the Cardew book on that. They did the best testing for the diesel effect in spring piston guns.

    If you don’t want to do the work yourself, I don’t know who works on Gamo airguns. Someone probably does, but I’ve never seen them mentioned anywhere.

    Keep us posted on how it goes.

    B.B.

  • Anonymous Says:

    Hi B.B. According to the latest edition of the blue book of airguns (5th edition),
    I noticed it mentions some design changes on the Beeman R1 using some weihrauch model hw35 parts to increase power,speed,cocking ease and efficiency,1st off has anyone noticed this change and how significant is it, also were the changes made to all 3 calibers .177,.20,.22 also I would like to know since the .177 &.20 are 12 groove & .22 is 6 is there a big difference accuracy wise I read of a gentleman shooting three quarter inch groups at 50 yards with his .25 if this person were using a .22 would a tighter shot group have been capable or are the .25 & .22 equal accuracy wise.

  • B.B. Pelletier Says:

    That’s a tall request. I will take awhile. Might even make a posting of it.

    B.B.

  • B.B. Pelletier Says:

    Okay, mystery solved.

    The R1 was NOT redesigned recently. It is “…an adaptation of the HW 35 that greatly increases velocity, reduces cocking.. ” blah, blah, blah. In other words, the somewhat clumsily worded R1 description applies to ALL R1s. Sometimes they have to cut words to get the pages to come out right and some editing can go awry like this.

    Now, your other caliber-related question still needs an answer, so I’ll make a posting of it.

    B.B.

  • backyard hunter Says:

    Is the RWS 54 a barrel drooper like the 48 and 52? and why havent you done a review on RWS and the quality of there rifles? i think everyone would enjoy that. Thanks

  • B.B. Pelletier Says:

    backyard hunter,

    I ASSUME the 54 is a drooper, but since I haven’t tested one, I can’t say for certain.

    Thus far I have reviewed the following RWS rifles and pistols:

    Diana 35
    Diana 27
    Diana P5 Magnum pistol
    Diana 46

    I’ve also covered the Diana 350 Magnum and the Diana 48/52 in detail in several posts.

    Still, there’s always room for more, and that’s what keeps me going.

    B.B.

  • Anonymous Says:

    Good to see someone explain “barrel droop” correctly. I noticed that my (fixed) barrel was true, but not aligned with the receiver. I commented about this on the “other” forum and was insulted by posters. Barrel droop can also cause poor breach sealing on fixed barrel guns. This can be a real problem on guns with hard delrin breach seals such as some KL3bs. Some people on the “other” forum even talk about BENDING barrels that have a droop. This is not a good idea.
    It is also good to see that you do not display a posters IP address. Hackers and malware pushers troll forums that display IP addresses!
    Thank you for your good work.

  • colt535 Says:

    What can you do about barrel droop? I bought a Korean rifle at a auction. It was new and the action works great. I can’t sight it in with a scope, red dot sight, or the factory sights. I can’t take it back to the auction because they closed. The company has no website. The groupings are always 2.5 inches from where I aim all the time even with scopes etc..

  • B.B. Pelletier Says:

    colt45,

    You need an adjustable scope mount. The mount slants the scope downward (in your case) to bring the strike of the round up.

    The downward slant is very common in pellet rifles, and not just breakbarrels, either. Two and a half inches at ten yards (I assume) is pretty typical. I’ve seen 4.5″!

    B.B.

  • Anonymous Says:

    I just picked up a rws 48 on clearance, without a scope. I’ve read lots of comments on difficulties of scope mounting due to droop. I’m sure the RWS c-mount is right for the application, but the accushot are listed on the pyramid site – which are much cheaper. Should I find a scope first before deciding on the mounts – and do you have recommendations for recreational target shooting out to maybe 100 yrds?
    Thanks
    ozark22

  • B.B. Pelletier Says:

    Ozark,

    Don’t be so sure that the RWS C-Mount is right for the 48! There have been three designs of C-Mount over the years and not all of them perform well.

    To stop the mount from moving backwards on the base, you must hang a scope stop pin IN FRONT of the scope base on the rifle.

    Diana didn’t design this base for scope mounting, and RWS USA didn’t understand the problem (they do now!).

    Pyramyd Air is developing a nerw scope mount that should solve the problem for all Diana spring guns, but for now just get a one-piece mount witha vertical scope stop pin.

    B.B.

  • Anonymous Says:

    Thanks BB -

    I notice that the pyramid site lists an Accushot 1-Pc Mount w/30mm Rings, High, 11mm Dovetail – under accessories for the gun now – are they the ones you mention? They’re much cheaper than the c-mount / bsquare AA.

    Thanks,
    Ozark

  • B.B. Pelletier Says:

    Ozark,

    Yes, those are fine if they fit your scope. They don’t adjust, but you can shim under the back of the mount to get some droop.

    B.B.

  • Charles Says:

    Barrel droop is a GOOD thing when mounting scopes on air rifles because air rifles normally shoot quite close compared with firearms and require absolute minimum parallax error for good accuracy when varying the distances of your shots. Parallax error is caused by the center-line of the scope not being the same as the center-line of your gun's barrel (bore). The closer-in you shoot, generally, the more significant this error becomes. However, the closer you mount your scope to your barrel's bore, the less parallax error will be a problem to shot placement at you go from one distance shot to a different distance shot. Because the scope is mounted behind the barrel, when there is a built-in barrel droop (as on RWS Diana air rifles, like my model 54) this forces one to mount the scope at a canted angle with the front of the scope down to sight the scope in properly. Now, when the barrel is drooped forward (down at the front) AND the scope is canted to match that angle, this is a nice design-engineered trick to bring the center-line of your scope closer to the bore-line of your air rifle and this, in turn, reduces parallax error. Reduced parallax error makes shot placement more accurate when shooting at different air rifle distances. So, barrel droop is a good thing, not bad. We have often complained about barrel droop, but the RWS engineers are not to blame for this good feature. It WOULD have been nice if RWS Diana folks had provided a scope base with the rifle which compensated for barrel droop which actually worked (RWS C-mounts don't generally have a good reputation, but there have been three c-mount RWS versions with some less bad than others). Now that UTG Leapers makes their great 11mm dovetail to Weaver-picatinny scope adapters specifically for your RWS model with your model's droop compensation built-in, we can now rejoice at reduced parallax error made possible by barrel droop without suffering mounts which don't hold zero or having to pay alot. At this time, Pyramyd sells these UTG Leapers adapters for just $17.50 which may be the best money you can spend on your RWS Diana air rifle if you want a scope which does what it should. Shoot safe – always keep your barrel pointed in a safe direction which also means a direction in which no-one is likely to cross. Charles

  • Anonymous Says:

    Barrel droop is actually caused by the mass of the barrel over its length being affected by gravity. The extent of the droop affected by the strength and ductility of the metal and the degree of hardness is has been given during the quenching and tempering process during manufacturing. This is not new to air rifles and has been around since the first guns & cannons were invented. Just ask any metalurgist, engineer or artilleryman. Movement in any direction other than down is NOT caused by barrel droop.

  • FRED Says:

    Anonymous, I would tend to agree with you, especially if we were discussing a 15" gun on a battle ship. It's thought that barrel droop is caused by a number of other conditions, as BB discussed in his blog. RWS rifles seem to suffer more barrel droop than any other manufacturer and this gentleman solved his problem thus:

    http://www.network54.com/Forum/419052/message/1203813573/Barrel+droop+fix+by+Scottg%2C

    Anonymous, most of the participants on this blog don't monitor these older blogs (this one was posted back in 2006). There are a core of volunteers, I being one of them, that do monitor them to address current comments. If you would like more responses to your post, you'd be much better off posting on the current blog. , even if your comment happens to be "off topic". It can always be found at:

    http://www.pyramydair.com/blog

    Welcome to our airgun blog. We look forward to you participating on it.

    Fred PRoNJ

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