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How much down angle does a typical AR-15 have?

This is a special guest report from Philip Pages of STNGR Industries, LLC. That’s pronounced Stinger. Today Philip will tell us about the droop in a typical AR-15. He calls it down angle.

STNGR has a blog that Philip tells me gets around 30,000 visitors each month. For a shooting sports blog that’s pretty active. He asked to write a guest blog and I suggested this topic for some reasons I will reveal at the end.

If you’d like to write a guest post for this blog, please email me at blogger@pyramydair.com.

Take it away, Philip.

How much down angle does a typical AR-15 have?
By Philip Pages

STNGR YivinxkYIDc unsplash
An AR-15 with a 10.5-inch barrel.

This report covers:

  • What is down angle?
  • Trajectory
  • Definitely not what we’re aiming for (pun intended)
  • A LOT of barrel options out there
  • So, what’s the standard down angle for an AR-15?
  • Of course, this is just a rough estimate and your mileage may vary
  • Why this guest blog?
  • Frustrated shooters

When it comes to firearms, there are many different options on the market for consumers. One of the most popular types of firearms is the AR-15. This weapon has become extremely popular in recent years due to its modularity and versatility. From different barrel lengths to a plethora of aftermarket accessories such as handguards to different chambering options, the possibilities are endless. So much so that building an AR-15 has become known as “Legos for adults.”

However, one question that often arises is how much down angle does a typical AR-15 have? Down angle is something that those familiar with airguns know a lot about.

But does that same principle translate to the AR-15? In this blog post, we will explore that question and give you some insights into the down angle of this popular firearm.

What is down angle?

First, it’s important to define what exactly “down angle” is. In the context of airguns and firearms, down angle is the difference in elevation between the muzzle of the gun and the point of impact. In other words, it is the angle that the bullet will travel in relation to the ground. The higher the down angle, the more horizontal the trajectory of the bullet will be.

Yards down range
A lot of factors can affect down angle, such as the type of gun, the type of ammo, the weight of the bullet, and even the weather.

Trajectory

Another important point is that, contrary to popular belief, bullets exiting a rifle’s barrel do not fly in a straight line. Rather the flight path follows a parabolic arc similar to the trajectory of a thrown football.

Think about it this way. As soon as the bullet leaves the barrel, it is immediately impacted by a host of factors such drag, muzzle velocity, gravity, wind and even the external temperature. Not to mention factors such as bullet size, shape and weight.

That’s why precision shooting is so difficult. A seemingly small and insignificant change in any of these factors will be magnified over a few hundred yards which could translate to being off target by multiple feet.

Definitely not what we’re aiming for (pun intended)

So do AR-15s have down angle? And if so, how much? The answer to the first question is yes! However, the next part is a lot more complicated.

Remember how I said that AR-15s were so popular because of how modular and customizable they are?

Well I wasn’t kidding. For example, a quick google search reveals that an AR style firearm can be built with barrels in the following lengths: 20″, 16″, 14.5″, 10.5″, 7.5″… you get the point. 

A LOT of barrel options out there

And that’s just the barrel length. Different barrels, even those of the same length, can have different twist rates. For example, a 16″ barrel from brand A can have a twist rate of 1:8 (one turn of the rifling in 8-inches of bore travel) while another 16″ barrel from brand B may have a twist rate of 1:7.

Each of these barrel lengths and twist rates changes the exit muzzle velocity which alters the bullet’s flight path which in turn changes the required down angle when zeroing the weapon.

Shop SIG Sauer Airguns

So, what’s the standard down angle for an AR-15?

Unfortunately, there is no definitive answer to this question. Like we said before, there are just so many different factors at play that it’s almost impossible to determine a universal standard.

However, we can make a few generalizations. For example, most AR-15s will have a down angle between 0-30 minutes.

Of course, this is just a rough estimate and your mileage may vary

Hopefully this gives you a better understanding of down angle and how it relates to the AR-15.

At the end of the day, airguns and AR-15s share a lot of the same similarities. A lot of the principles learned from shooting airguns can be applied to AR-15s and vice versa. That’s the beauty of shooting sports, the skills are so transferable.

Why this guest blog?

This is BB talking now. I asked Philip to write this blog because we airgunners jabber about “barrel droop” all the time and I have often said that firearms have the same problem. Today he has addressed it. In case you didn’t catch it, down angle in the first paragraphs is different than trajectory, though they both do similar things — drive the bullet lower than the point of aim. But firearm bullets move so fast that at typical airgun distances of 0 to 50 yards the droop or down angle doesn’t stand out that much. Please note that Philip says an AR-15 can have 0-30 minutes of down angle. That’s droop, folks.

Frustrated shooters

I see this at my rifle range a lot. A guy brings out a new AR and a new scope, and he either mounts it right at the range or at home just before he comes. Then he tries to sight in at 100 yards and discovers his bullets are impacting 12-inches low. Sometimes it takes a lot of shots before he realizes that, because he wasn’t expecting it. So, what does he do? He does what all of us once did — he cranks in 48 clicks of elevation (quarter-minute clicks take 48 to raise the impact of the bullet 12 inches at 100 yards — yes, I’m being sloppy about yards and meters, but that’s not the point).

If his scope is a premium one that’s also new he may have solved the problem. If it’s an El Cheapo or a scope he took off another rifle (i.e. it’s been adjusted already), he may have relaxed the scope’s erector tube return spring so much that now his rifle will not hold a zero. The erector tube and therefore the reticle bounces around with every shot. And finding that out takes a lot more ammo! When that is discovered he usually blames either the rifle or the ammo or both.

I once helped a guy in just that situation. He was shooting about 6-inches below his aim point at 100 yards. We made some makeshift shims that got him on the point of aim without all the extra elevation adjustment. There was some but not as much as before the shims. But 30 minutes of down angle? There is no way to shim for that! 

My thanks to Philip for today’s blog it’s an interesting subject of which both airgunners and firearm shooters need to be aware.

38 thoughts on “How much down angle does a typical AR-15 have?”

  1. B.B. and Philip,

    Before Flat tops I had the Smith give me a 20, 25 or 30 MOA Picatinny rail where the handle used to be. The best solution is to specify a rail that corrects (most of the aiming error) or use a set of adjustable scope rings/bases. I also had different front posts made for my Vietnam era Mattel-o-Matics (just for RidgeRunner) just like all my other Service Rifles. I let the unit/squadron armorers know that messing with my sights/sighting system was VERBOTEN!

    shootski

  2. FX makes a variable angle rail. Why not just use that?
    Friend of mine who retired to a farm has an AR-15 with a fancy “bull barrel”. He says 1 MOA. I shot 3 MOA at 300 yards. What is the effective range(yes I know cartridge and barrel dependant), but a round number average?

    Thanks,

    -Yogi

    PS fastest twenty bucks I ever spent!

    • Yogi,

      3 MOA at 300 yards is about a 9″+ group…is that what you meant?
      There really isn’t any ballpark number since the platform shoots so many different caliber rounds and powder loads.

      shootski

    • Yogi,

      I have killed a deer at 250 yards with a Springfield bolt action rifle chambered in .223. I hit him in the neck at the base of the skull (where I aimed). This was a free floated, bolt action rifle with anal hand loads. I frequently shot groundhogs in the head out to 300 yards with that rifle. After that, the drop became so significant I would not bother.

      1 MOA at 100 yards with a Mattelomatic is good.

    • Yogi,

      For entry-level ARs I guess the average would be about 2 MOA. My bull barrel AR that’s designed for past 600 yards is 0.3 to 0,7 MOA at 100 yards and 1 to 1.5 MOA (with me shooting) at 200 yards. But I shoot 69-grain bullets that are loaded so long they must be loaded single into the chamber.

      BB

    • Yogi, good shooting. It seems to me, effective range for any gun has to include what you are shooting at and what you need the projectiles to do when they get there. Target shooting vs hunting, for example. If hunting, the bullets still needs to have enough “oomph” to do its job reliably and ethically, and the size of the animal will inform the size of the group you need to maintain, groundhogs vs deer, for example. Shooting at targets seems to me to be a simpler question as all you need to do is penetrate paper or ring steel.

  3. The way it was explained to me that made it real clear was that if you shoot a rifle perfectly level the bullet fired will hit the ground at the same time you drop one from your hand from the same height.
    When I first got my stock Colt A2 I decked it out with a detachable rail for the handle, scope, a Colt Delta HBAR cheek riser with the cut out for the charging handle, a quad rail, sling and bipod. Heavy, yes but recoil was nice. Later on I thought, this was supposed to be a defense/offense weapon ? Who cares about 100 yard accuracy, really don’t have to worry too much about a person that far away. Unless, I’m his target !! I guess.
    Anyway It now has a shorter barrel, flat top, dot sight and adjustable stock. AKA Carbine. Save the 308 for things that far away that need attention.

    • Just realized the scope I had on the AR15 at the time may have been a CenterPoint TAG 3-9×40 bullet drop compensating out to 600 yards. I remember a shinny one? May be too new but it was on it at one time. Getting old.
      Actually No, the dots are missing from the lower reticle. Must have been an earlier TAG scope. Still newer ones are a noteworthy scope for long range use. and not too costly.

    • Bob M what a fun example of gravity.

      Then I had a thought, what about the relative time for those two bullets? As the fired bullet travelled much faster, it’s time passed relatively slower. Therefore it took longer for the simply dropped bullet to arrive on the ground. Oh what fun… 🙂

      • hihihi
        I’m going with Roamin Greco on the bullet speed time warp thing.. But hey, things would definitely be different if you were shooting from the rim of the Grand Canyon. 😉

  4. BB-

    30 minutes of angle would only be one half of one degree. So, yes it could be shimmed. Better solution is a Pic rail with the desired correction angle. Lots of variables to be considered to make the line of sight coincide with bullet impact. Some styling trends make it more difficult for airgun shooters with their (usually) shortened pellet trajectories. First is the trend to larger scopes, in both body diameter and objective size. This raises the line of sight in relation to the bore axis. Another trend is for shorter overall length of guns. The closer the muzzle is to the scope’s front lens drastically affects the geometry.

  5. OK, even though I (think I) know the answer, I’m going to ask anyway. Assuming that the line of the bore is not parallel to the line of sight, and the trajectory is a parabolic curve downwards, I thought barrel droop was the difference between the line of the top of the receiver and the line of the bore. For example, if you mount a scope without any droop compensating mounts, I would assume that the line of sight is parallel to the top of the receiver (if the dovetails are properly machined), but the line of the bore (perhaps exaggerated in breakbarrels) “droops” downwards from those lines. Then the curve of the trajectory is even lower than it would be if the bore was parallel to the line of sight and the top of the receiver. In fixed barrelled guns, this droop might be more or less, but hopefully minimized by manufacturing methods to line up the barrel (and hopefully the bore) with the receiver. I always figured this is why the rear sight was on the barrel and not on the receiver of most guns, to minimize the effect of this droop vs. the line of sight. And I have to say, as an avid follower of the articles written by Jim Carmichael in “Outdoor Life” and David Petzal in “Field and Stream” over the last 40 years, I never heard of the problem of adjusting a scope so high as to relax the erector. The first time I read about that was in this blog, and many times since, especially in reference to mounting a scope on the receiver (note, not the barrel) of a breakbarrel airgun. So I guess I have been confused on what we are specifically calling “droop” and whether that is moot.

    • I guess what confuses me is the diagram of “down angle,” while typical of the illustration of trajectory, doesn’t really show the barrel drooping. It actually shows the barrel pointing up relative to the line of sight.

    • Roamin,

      You may never have heard of it. I have done it repeatedly, both intentionally and by accident.

      But keep adjusting up and wonder why your rifle won’t stay zeroed.

      BB

        • Roamin,

          I wasn’t lecturing, but it sure reads that way. Go ahead and question. I once had to correct someone who read from I think George None, a gun writer, about the intricate one-way valve in a spring-piston rifle.

          I think perhaps a blog on this with some proof is in order?

          BB

          • BB,,, and RG, as well,

            I think I understand droop, as it happens in break barrel,, and even some that aren’t break barrels. But what RG said about barrel to receiver alignment seems correct to me. In the above article, Mr. Pages never struck on this phenomena. I think there must be some misunderstanding on my part.

            Ideally, the bore of a barrel should be parallel with the receiver, and it is in most PCPs and rifles I have handled. This is quite easily seen using long straight edge,, like a four foot level. The droop,, or “down angle” will be seen,, if it is significant. But this is only if this is the “down angle” Mr Pages was referring to.

            Still confused, I guess.

            Ed

          • No offense taken. Just trying to understand. Pictures always helpful. I have a small collection of powder-burning and air rifles now, perhaps I can find a way to measure what I understand to be barrel droop and show it in pictures or in a diagram and we can compare notes.

      • This is so relevant to FM’s recent “stupid is as stupid does” experience! Make long story short – since FM IS short – mounted the CenterPoint scope that came with the recently acquired Benjamin Maximus .22, the “Hunter” version and tested scope and rifle in the backyard shooting at a 25-yard pistol target – from 25 yards. The first group of 3 Crosman Premier HPs (14.3 grain) impacted outside the target rings, very low about the 5 o’clock position. The group was 1″ or less which for FM was satisfactory. The scope had not been adjusted at that point.

        Then FM got going with the “elevation and windage clicking ritual,” yet the results got worse and worse so that eventually pellets were missing the target and the backstop. Moving the target to 15 yards did not help. Thought the scope was messed up or FM had screwed it up. So, consulted with my enabler-friend Gunfun, who requested some pics of the scope mounted on the rifle and, well, the emails tell the story. Bottom line: when mounting your scope, make sure up is UP and side is…on the SIDE. Back for another zeroing-in session this weekend. Hope this gives all who read it a good laugh.

        From GF1 – ”
        When you are shouldering the gun to shoot you need to rotate your scope 90 degrees to the right. Then the scope will adjust right.

        You have the up adjusting knob on the left of the gun. It should be facing straight up and the windage adjusting knob should be on the right side of the gun.

        When you do that the scope should adjust correct after that.”

        From FM – ‘thought to look for your reply right after reading this morning’s airgun blog, since Tom talked about excessively adjusting a scope so as to relax the erector tube and seemingly losing your “zero” forever.

        I really appreciate your help because the error is so simple, the possibility of mounting the scope with the adjustment wheels BACKWARDS went right over my SIMPLE brain – feel like a dumbass with an oversized dunce cap on! Either that or getting blind as a bat – let’s call it a DSM (Double Senior Moment) for me. “Fawlty” Manuel is a good nickname for your friend here. Speaking of Manuel, did read the manual that came with the scope, but if it mentioned how the adjusters were to be positioned, sure missed it. So, back to the backyard by this weekend. Hope FM did not mess up the scope. My friend-boss who’s legally blind but can shoot with a good scope will laugh at this story. Don’t think he’s ever made this mistake.

        Take care and many thanks for your always good advice.”

    • Exactly right! Break barrels have an excuse. Others don’t. A company that knowingly builds in droop should be avoided. I think most droop happens due to misalignment of bases. That is poor quality control.

      I don’t own an AR15 and am not likly to. The lego aspect has been a lure that might get me…someday. I am old fashioned, wood & blued steel! I am ready to repel boarders with an 1100 & 00 buck.

        • If the wildfires keep going, there may be no trick or treating this year in NM. I wouldn’t t or t at my house either.

          Funny, but the only monsters that have visited have been bears. I put up a powerful security light last year. Now, no more bears. I have 5 hummingbird feeders out and none have been torn down this year. Umarex & Hatsan have been protecting feeders by day.

  6. Noticing that on my phone a reply takes me down to the bottom of the comments now rather than opening a box just after the comment I am replying to. I liked the old way much better.

  7. Completely off subject but completely frustrated. Does anyone know how to copy or insert or paste a photo or even an emoji using an IPad in comments?

    Thanks in advance!

    Deck

  8. The 5.56mm/.223 is obsolete now, the military is going with the Spear in 6.8 mm. because of a thing called body armour. About the same as a .308, but at over 80K cup it needs special stainless/ brass case and special powder, it uses a 13″ barrel, and cost $8K . 12K round barrel life. Not really intended for civilians, a step in the right direction I’d say. Deers dont wear body armour, and a big bear doesn’t need to, especially in tight brush. Stick with prayerie dawgs. 1stblue

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