Point Of Aim For Distance 1911 Shooting?

[Duane Thomas]

Yeah, that really doesn't make sense. With any sort of factory ammo, or .45 ACP handloads in the Major power range, the bullet should still be rising at 25 yards. It could be the OP's sights are hitting low for him, but at close range, especially with fairly large targets, the deviation is not enough to show, or is masked by overall group size. At 25 yards it is obvious. That strikes me as the most likely explanation. Either that or there's a bit of pre-shot anticipation going on that, also, doesn't really hugely evince itself at close range.

Raymond, are you benching the gun at 25 yards, thus to factor out any possible human error factor, or shooting freestyle? If the gun hits low from the bench, your sights need adjusting. If it doesn't hit low from the bench, but does when shooting freestyle, it's a software and not a hardware problem.

[RaymondMillbrae]

Thanks, guys.

I now understand the fact that the .45 ACP bullet stasrts to drop AT ANY DISTANCE, or the moment the bullet leaves the support of the barrel. (Gravity is now in full force).

I've also known the fact that the bullet will cross the POA two times. At the beginning of the trajectory, and towards the drop of the trajectory at further distances. (Basic training, 1983ish).

I guess what I didn't really understand was that the bullet IMMEDIATELY starts to drop the moment it is fired. And I also didn't consider the fact that the sights, and the barrel, are not perfectly parallel to each other. (From the git-go, the barrel is slightly sloped upward).

But let me take it one step further...I have another thread going, and I am installing a Dawson Precision FO front sight onto my Nighthawk Predator. And when I measured the existing sight, it was .180T. - which is the sight height I ordered from Dawsomn Precision.

But the Dawson Precision folks told me that it was the wrong sight height for a fixed rear sight. (Which is what I have). And they were surprised that the Nighthawk folks had installed that front sight height on my weapon.

The Dawson Precision folks told me that .180T is for ADJUSTABLE REAR SIGHTS, and that .160T are for FIXED REAR SIGHTS. (They even asked me how it shot - which was low, of course).

Long story short...they are sending me out the correct-sized .160T front sight that belongs with my fixed rear sight.

This explains why my "in your face" shots were spot on...but my distance shots were always kinda low.

This new front sight (.160T) should bring my distance shots up a bit.

Thanks again, it was an informative thread.

In Christ: Raymond

Edited November 21, 2009 by RaymondMillbrae

[amaziah]

Hey Ray when you received this gun new or new to you did you sight it in? That is the first thing I do whenever I get a new gun to see how it shoots. You would have noticed immediately that the gun shoots oddly if you would have sighted it in at 25 yards or 50 yards. :-)

[Duane Thomas]

I guess what I didn't really understand was that the bullet IMMEDIATELY starts to drop the moment it is fired.

That's because the bullet doesn't immediately start to drop the moment it's fired. It starts to rise the moment it's fired. It just doesn't do that because velocity by itself somehow causes it to rise. It happens because the barrel is tilted slightly upward.

[ima45dv8]

The sights on the gun ride a distance above the barrel. The makers of guns know this. If the barrel inside the gun was perfectly level relative to the sights, but below them, you could never have point of impact/point of aim because the bullet would always hit below POA. POI would begin below POA, then as gravity had its way as distance increased, POI would become progressively lower.

Knowing this, gun makers actually angle the barrels of their guns slightly upward relative to the sighting plane. The idea being that at some point the bullet, moving upward, will cross the sighting plane and, at the point, you'll have perfect POI/POA integration.

As the bullet leaves the barrel it is travelling upward, but only because, to a minor extent, it's actually being fired upward. At some point in its flight, gravity overcomes this effect and the bullet begins to drop. The bullet doesn't really shoot flat at any point in its travel, its path describes a shallow parabola, up then down.

There are actually two points at which you'll achieve perfect POI/POA integration, two distances: in close and at a much greater distance. The bullet leaves the barrel travelling upward, then it crosses the sighting plane, that's the first point at which POI/POA come into alignment. The bullet continues on past that, at which point it actually travels above the sighting plane. Then as gravity asserts its hold and the bullet begins to arch downward, the bullet crosses the sighting plane a second time.

So, basically, the progression of POI/POA relationship goes like this:

(1) In close, bullet impacts below POA.

(2) First point of integration, bullet hits exactly POA.

(3) Beyond that, bullet hits above POA.

(4) Second point of integration, bullet hits exactly POA again.

(5) Beyond second point of integration, bullet hits below POA again.

Nicely stated.

With communicative skills like that you should consider becoming a writer.

[North]

[Guy Neill]

The bullet begins to drop the instant it exits the muzzle of the gun.

Think about throwing a ball. To throw it farther, we throw it higher. Watching the arc of a ball is seeing the path of a slow moving projectile. A bullet will follow a similar path, but we can't see it because of the much higher velocity.

One thing that causes a great deal of confusion is the use of the term "drop" when describing the "trajectory," and many ballistics programs and tables make this mistake. Drop is simply how far the bullet falls. Trajectory is the path it takes to the target, related to the line of sight. I really wish they would not interchange the terms.

If we take gravity as constant (good enough for most purposes) at 32.174 fps², we can determine the time it takes the bullet to fall a given distance (neglecting air effects). If the bullet is fired parallel to the ground, meaning that the trajectory values equal the drop values, with the barrel 3 feet above the ground, it will take the bullet 0.0538 seconds to hit the ground. The bullet will never rise above the boreline since it starts at the boreline and falls from there.

If the bullet is fired from the parallel barrel with a muzzle velocity of 800 fps, we can determine the bullet will travel just over 43 feet as it falls to the ground. If it had a velocity of 900 fps, it would travel just at 48.5 feet in the same fall time.

If we fire the bullet at an upward angle, there is a vertical component to the velocity that sends the bullet up until the gravity acceleration overcomes it. Since the gravity is constantly acting on the bullet, the path (trajectory) is arced (or parabolic as has been mentioned)

Also note that the barrel is pointed down compared to the sights. Recoil moves the gun far enough before the bullet exits the barrel to cause the barrel to be pointed up at the time the bullet exits.

It's the combination of velocity and muzzle elevation that gives us the trajectory and range capability of any bullet since gravity is constant.

Guy

[Duane Thomas]

Nicely stated.

With communicative skills like that you should consider becoming a writer.

Gee, I dunno.... Do you think I could, really?

[Duane Thomas]

The bullet begins to drop the instant it exits the muzzle of the gun.

One thing that causes a great deal of confusion is the use of the term "drop" when describing the "trajectory,"

If we fire the bullet at an upward angle, there is a vertical component to the velocity that sends the bullet up until the gravity acceleration overcomes it. Since the gravity is constantly acting on the bullet, the path (trajectory) is arced (or parabolic as has been mentioned)

So you're saying the bullet begins to "drop" as soon as it exits the barrel, in the sense that gravity instantly begins to affect its trajectory, even though it's still travelling upward?

Also note that the barrel is pointed down compared to the sights. Recoil moves the gun far enough before the bullet exits the barrel to cause the barrel to be pointed up at the time the bullet exits.

Interesting. I have heard the "barrel is pointed up relative to the sights" thing for years, and accepted it because it seemed to correlate with observed reality, but I had failed to factor in the human element of barrel rise as the bullet is travelling down the bore. So you're saying that, from a purely mechanical standpoint, most or all rifle or handgun barrels actually angle down slightly relative to the sighting plane?

Guy, thanks for your input here. It's amazingly valuable to get commentary from an honest-to-God ballistician.

[RaymondMillbrae]

Also note that the barrel is pointed down compared to the sights. Recoil moves the gun far enough before the bullet exits the barrel to cause the barrel to be pointed up at the time the bullet exits.

Now THAT is interesting!

I thought the barrel was inclined slightly UPWARD in relation to the POA.

In Christ: Raymond

[Guy Neill]

The barrel pointing down bit is easy to see if you get two wooden dowels or something similar and p[lace one in the barrel and the other on the sights. It's also fairly easy to see on revolvers, especially longer barreled ones, where the front sight gets taller. The recoil causes the barrel to be pointed up, with respect to the original line of sight, as the bullet exits the barrel.

Yes - gravity is always ON - it doesn't switch off for any period of time, so drop begins as soon as the bullet is not supported by the barrel. Remember, drop and trajectory are different - even though many charts erroneously use the term drop when they should say for trajectory or bullet path.

Guy

[Sam]

Nicely stated.

With communicative skills like that you should consider becoming a writer.

Gee, I dunno.... Do you think I could, really?

Hey, maybe Guy could do a little moonlighting too?

This has evolved in to a really good thread, I'm glad you started it Ray.

It is pretty amazing, the shooting minds that we can access here at BE.com.

All kidding aside, it is truly humbling. Thank you guys for posting here. -Sam

[Patrick Sweeney]

Barrel pitched up, barrel pitched down, it is all relative. On some; up. On others; down. It depends on the caliber (velocity and bullet mass) and range of use. If you're shooting on the 600 yard line at Camp Perry, your barrel is most definitely pitched up, vis a vis the sights. If you're sighting in an M-329 with heavy cast-bullet loads, your barrel is pitched down. (It will be very much up, momentarily.)

Each firearm model is a unique sample, and you cannot express the angle between sights and bore axis as a single angle for all.

[HRider]

This is a cool thread. Lots of stuff to get the brain working.

I have always thought that the gun did not recoil until the bullet exited the barrel (just my thinking, not based on anything that I read or was told from a learned person) because the bullet was actually pulling the barrel forward as it traveled down the bore. Now, as this was happening, the case was pushing back on the breech face with equal force, causing the gun to remain still (mostly, not talking about the torque from the rifling here) until the bullet cleared the muzzle. At this time, the pull on the barrel is gone and the push on the breech face takes over and the slide begins rearward movement ( and we know the rest of the 1911 cycle).

After reading this thread, I see that you are saying that recoil affects point of impact because the barrel moves before the bullet exits. I guess this explains why one person can zero a rifle and another will usually get a different point of impact with the same rifle.

Hurley

[Duane Thomas]

Exactly. At distance I can stand there and change POI, with the same handgun and load, just by varying grip pressure, thus changing how much the gun moves before the bullet leaves the barrel. The more grip pressure, the lower the POA and vice versa.

[RaymondMillbrae]

Hey guys,

here's the "current" deal:

I removed the front sight that came with my Nighthawk Predator and remeasured it. It was exactly .180T x .127W. (Based on my Dillon calipers).

Nighthawk had it zeroed at 20 or 25 yards. (I cannot exactly remember).

But Dawson Precision said they were the wrong-sized front sights (too tall) - so I ordered the correct height front sight from them, with a narrower blade. (.160T x .100W).

Upon my return from the range on Saturday, I found my new Dawson Precision fiber optic front sight in dee mailbox.

Thirty minutes later they were installed, and as Ricky Ricardo would say, "Looookeeng guuuuud". (Remember, "I Love Lucy")?

Anyhoo, I will be at Jackson Arms on Tuesday evening trying them out. (NRA member 1/2 price night).

Below are a few pictures of the sights.

All I can say is "WOW"!

I can even say it backwards, "WOW"!

The front fiber optic sight is crispy clear, and it stand's-out like you wouldn't believe. (My pictures do it no credit).

The narrower front blade is also a huge difference. I can see to the left and to the right of it - and I can actually see my distance targets now.

As for the front sight being lower...WOW! It was immediately evident that it would make a difference in my POA. I was playing with it, and now I can see the top of the slide when I aim.

I am excited to see the results/benefits of this new sight. Hopefully it will help to correct my distance shots from shooting low. (My "In Your Face" shots were never a problem).

Enjoy the pics, and I will follow-up Tuesday night.

Thanks again.

In Christ: Raymond

PS: I hope yall don't mind all the pictures I post that "bogg down" your computers. But like I told a moderator the other day - I understand that these posts are NOT just for me. When I ask questions, I try to do so in a manner that will be beneficial for other readers to understand, and I also add pictures to give a mind's-eye view to help in the process. It's NOT all about me...but it is for others to be edified as well.

Edited November 24, 2009 by RaymondMillbrae