This question isn't about which is a better choice but I have posted before about shooting my M&P F/S 9mm low at 15 yds. with 115gr bullets and some have suggested that I try a 124gr to raise it up I've been shooting for 50 years my understanding is the heaver the bullet the more drop and at 15yds. I wouldn't think
there would be much difference at all. But even at 67 I learn something almost every day.
HAVE A GREAT THANKSGIVING!

Actually, lighter bullets will shoot lower than heavier bullets out of the same gun, for the most part.

Your sights are lined up and you fire. The gun starts to recoil before the bullet leaves the barrel. A lighter bullet will be travelling faster than a heavier bullet so it will leave the barrel sooner, giving the barrel less time to rise up from recoil. The result is that the lighter bullet hits the target lower than where the heavier bullet hits.

Of course, other variables can affect this, like distance from the target, but that's the general idea.

Does that help?

I typically don't see a difference in bullet weight. What I do see is a difference in brand. Some brand of ammo may shoot a little to the left/right/up/down then another brand



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That's been my experience. I don't really notice a difference between 115 & 124gr within the same manufacturer, but I do notice a difference in accuracy between manufacturers.

I have never heard of this whole higher weight bullets hitting higher. don't all bullets leave the barrel before the gun recoils? I would think that if the gun recoiled while the bullet was still in the barrel, it would be highly inaccurate.

Although it seems that recoil should not occur until the bullet leaves the barrel, it actually does start the instant the bullet starts down the bore. Newton's third law of motion ensures that. Heavier bullets generally have lower MVs (assuming equal peak pressures) than lighter bullets, and therefore have a fractionally higher bore residence time. That means the recoil lasts marginally longer, resulting in higher muzzle rise at the time the heavier bullet leaves the bore. For identical sight settings, the bullet departure angle from the horizontal at that instant is greater for the heavy bullet, and therefore the heavier bullet strikes the target higher, at least at closer ranges.

It's more prominent in short-barrel guns. The best example is to look at a snub revolver, like a 642. Here's a picture of mine:



Look at how the sights line up compared with the barrel. If the sights are perfectly horizontal, the barrel will be pointing down slightly.

The reason the guns are accurate is because this is taken into account when the gun is sighted in.

Very interesting I like to see a pistol being shot in slow motion to see the barrel recoil before the bullet leaves the barrel I'am sure there's one out there.
Thanks Guy's

A quick search will reveal plenty of slow motion recoil videos, maybe my old eyes don't see it but it appears to me the bullet is well on it's way before the recoil begins to raise the barrel. Your mileage may vary.

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Back to back World War Champs.

There are indeed high speed pictures of guns being fired, and the barrel only rotates up .020 to .050" before the bullet departs, which is consistent with calculations involving the action-reaction momentum equation. Look closely at the slide/barrel at the front and you can see the slide just start to move back and the barrel slightly rise. If the gun had a linear recoil mount that prevented rotation, it would eliminate the effect of rotation causing barrel rise.
Contrary to "common sense", as often happens with real-world physics, the heavier pistol bullet DOES leave the barrel later when the pistol rotates in the hand, causing a slightly higher strike on the initial crossing of the line of sight by the bullet path. Naturally, the % difference between a 115gr and 124gr 9mm pistol bullet is small, smaller than can be detected shooting offhand at short range.
With rifles, the vibrations in the long skinny barrel dominate, with the muzzle pointing in different directions when different bullets depart. Browning made rifles with "tunable weights" on the barrel to address this issue.


Look closely at the pictures in this link, and you can see the semi-autos just starting to open, and the continued rotation causing the barrels already to point slightly up relative to the bullet axis. Remember, it is only a few thousandths of an inch. Especially note the underwater shot.
bullet leaving handgun - Bing images


In my experience with handguns, most times a handgun shooting several inches low at normal defensive handgun ranges (like 6" low at 20yds) is caused by the nut behind the wheel breaking down as the trigger is pulled, and getting the shot to hit an inch higher with a heavier bullet does not solve the problem. Shooting at 100 meters to sight for metallic silhouette, bullet choice matters a lot.

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Science plus Art

I hadn't given this much thought before but I may have proved it last night. Or at least proved the bolt is moving sooner than I thought. I had a few misfires with a M1 Carbine. (It was the handiest at the time.) The dogs were putting up a big commotion in the front yard so I grabbed the M1 and went to the porch. There about 15' from the porch was a well fed rattler.

In the process of doing away with the threat, I had three misfires out of five shots taken. I collected the brass and misfires this morning. After examining the rounds, I saw that the misfires had a full and deep depression in the primers. The rounds that did fire had a lighter depression. I can surmise that the bolt starts moving back at the instant the primer/powder fires even as the firing pin is still moving forward.

Not exactly. The operating rod starts to move rearward as soon as the bullet passes the port and pushes the tappet rearward, but the bolt has not unlocked and begun to open until after the bullet has left the muzzle. But the recoil started as soon as the primer went "Bang!"

Just to keep the Safety Police from jumping my case about shooting from the front porch, I live on acreage out in the "sticks". Cougar, feral dogs and coyotes are frequent visitors. And I'm well aware of soil conditions and angles of fire.

Ummmmmm. Yeah, I can buy that. Why then did the fired rounds have a lighter impact on the primers?

Never mind. I think I see what happened. After closer (magnified) examination of the rounds, the primer on the fired rounds look flattened out. Perhaps pressure on the bolt? It makes it look like the strike was lighter. The primers on the unfired rounds look bulbous.

Added: I can try to get pictures if anyone is interested.

The fired primers had a small explosion inside of them trying to blow the dents back out. The dud primer had the full impact of the firing pin but no push back.

Yep.

I'm learnin'.

Simple physics are at play here.
The lighter bullet is easier to get moving from a dead stop than a heavier bullet. Remember 9th grade science class? For every action there is an equal and opposite reaction. - ie recoil. So if it takes a greater shove to start the heavier object into motion there will also be a heavier shove in the opposite direction. This opposite shove is the recoil. Now, since the lighter bullet has less mass it also achieves greater velocity in a shorter time period than the bullet with more mass does. Therefore the lighter bullet will exit the barrel before a heavier one will. You take that along with the increased recoil and what you end up with is this..
The gun is in a higher arc due to increased recoil with the heavier bullet, along with the heavier bullet starting out slower than a lighter bullet = the muzzle is pointing higher as the heavier bullet exits the muzzle. So, because of this simple science heavier bullets at close range will as a general rule print higher on the target than the lighter bullets. This can change should you bump up the powder charge in a cartridge loaded with a lighter bullet to make the gun recoil more and raise the POI also, but it is always caused by recoil or lack thereof. If the gun was locked in a vice where it couldn't move at all there would be no increase or decrease in POI between light and heavy bullets at close range launched at the same velocities.

This explains it all.

I've never noticed a difference between the two. In most cases the 115 gr travels faster than the 124 gr. Which means less bullet drop. But at 15 yards the bullet drop is negligible for both the 115 and 124.

No offense, but have you bench rested the gun? Can't be sure until you do. I bought a brand new M&P a few years ago that shot four inches low at ten yards no matter who shot it. Had to send it back to Smith.

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I have had 115gr shoot low and 124gr shoot high in my 9mm's.
I have also had 115 and 124gr reloads both hit at the same POI.

A certain load can be raised or lowered by changing the fps with
different powders, some more than others.
The problem is, that there is also the possibility of the load
moving left or right from the faster or slower load.

I have a 147gr plated that shoots several loads at POA but this
larger bullet also has more recoil than the lighter 115gr.
It works for me but the girls in the family like the lighter 115gr
at light target speeds for their work.

G'day Mate...Whats a porch???

This is a porch.


It's a place in front, back, or even the side of the house where people can gather or one can sit peacefully by himself. Normally covered but not always.

So what do you folks down under call it?

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Bullets all drop at the same rate. Leonardo da Vinci proved that by dropping two different balls off the Tower of Pisa. It's the DWELL TIME of the bullet in the barrel. A faster bullet leaves the barrel before the gun has had a chance to recoil as much.

Bullet drop through the air is more a function of velocity affecting time of flight, therefore more time affected by gravity. We can't change drop rate, but we can alter trajectory to compensate for it.

Another factor is air resistance. A blunt bullet will slow down faster than a pointed one, spend more time in flight and is affected by gravity for a long time.

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I've have one of the Sig P6's in 9mm. 115 grain bullets shoot a little low for me. 124 grain bullets shoot to the sights. Proved this to myself many times while at the range. The sights on this pistol are only adjustable for windage. Frank

Oh ok...We call that a verandah!

The difference is, on a porch, you don't have to keep your pinkies extended.

Good info. Thanks for the clarification to all.

I think you are correct! More then likely a one handed gut shot!
Or a couple in the upper chest region.

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