Having trouble with my...

[JohnKSa]

A heavier bullet (147 gr.) will also raise the point of impact a little...

While different bullet weights will generally make a significant difference in point of impact in revolvers, the difference in locked breech autopistols is much less noticeable. That's because the initial phase of recoil during which the bullet is still in the bore results in very little muzzle rise. The slide/barrel initially recoil nearly straight backwards without much muzzle rise until the barrel unlocks. The bullet is out of the bore by then.

Revolvers tend to show muzzle rise as soon as the bullet starts moving and therefore changing bullet weights (or changing anything else that affects recoil significantly) changes the point of impact significantly.

It wasn't until I actually charted sight lines vs bore lines for a couple of revolvers and autopistols that I realized that they were very different in this respect.

 

[Walt Sherrill]

While different bullet weights will generally make a significant difference in point of impact in revolvers, the difference in locked breech autopistols is much less noticeable. That's because the initial phase of recoil during which the bullet is still in the bore results in very little muzzle rise. The slide/barrel initially recoil nearly straight backwards without much muzzle rise until the barrel unlocks. The bullet is out of the bore by then.

Perhaps I misunderstand the mechanics (physics?) of the situation -- always a possibility for me in these discussions... Those who have a better explanation, help me understand, if I mis-understand...

As I (mis?-)understand it, there is still recoil and muzzle rise with lighter or heavier bullets, but because the barrel and bullet are both moving slower with a heavier bullet, the heavier bullet typically takes a bit longer (time) for the bullet to leave the barrel and the barrel will rise a bit more in recoil. In either case, the bullet WILL leave the barrel before it starts to unlock, but arguably with about the same amount of slide/barrel travel.

I don't think the difference in POI will be great with a close target, but faster lighter bullets get there more quickly and the barrel will have risen fractionally less by the time the bullet exits the barrel. So we may agree on what happens, but disagree a bit on how much EFFECT it has... In an earlier discussion here, one of the moderators made this point:

But in a handgun, barrel time affects the point of impact. The lighter/faster bullet gets out of the barrel before the gun recoils very much, so it strikes lower. The heavier/slower bullet is later getting out of the barrel and so the gun can recoil upward more and the bullet strikes higher.

As for revolvers and semi-autos, the difference is mostly seen/felt AFTER the bullet is on it's way.

Why after? If the barrel hasn't unlocked in the semi-auto by the time the bullet has left the barrel, the main difference between the semi-auto and revolver is bore axis. That shouldn't have much effect on POI in one or the other handguns, but it does have a noticeable effect in how much the revolver muzzle rises AFTER the bullet has left the barrel. You make that point. The speed of the bullet also affect muzzle rise -- with heavy rounds moving more slowly.

I think of the revolver as a barrel with a long handle with the shooter holding the end/base of that long handle. The the semi-auto is a barrel with a short handle. Once the bullet leaves the barrel, recoil -- which began when the powder was ignited, continues, and the longer distance between grip and barrel creates a bigger ARC with the revolvers than the semi-auto. It looks and feels different. But, POI shouldn't be that much different between the semi-auto and revolver, as that they are just alike until AFTER the bullet is gone. (Barrel length can play a big role here, too.... so we should be trying to keep most of the variables as similar as possible.)

Apparently, the revolvers with a barrel at the bottom of the cylinder have noticeably less barrel rise than the revolvers with a much higher bore axis.
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[JohnKSa]

In a typical locked breech handgun, the slide and barrel initially recoil straight back. It's not until the barrel hits the stop (which happens after the bullet exits) that the muzzle begins to rise.

Until the barrel hits the stop, there's nothing to make the muzzle rise because the barrel and slide can move straight to the rear essentially unhindered by anything other than the relatively small force of the recoil spring.

When the barrel stops, that force is transferred to the frame which is being held in place by the hand from a point below the bore. Then the recoil force will cause significant muzzle rise to begin, but the whole point of the locked breech design is for the bullet to be out of the barrel before that happens.

In a revolver, the barrel is fixed to the frame and the hand resists the recoil from a point below the bore. So the recoil in a revolver results in muzzle rise that starts as soon as the bullet starts to move.

Take two UNloaded guns, one locked breech semi-auto and one revolver. Hold one in your strong hand in a shooting grip.

Push on the muzzle of the semi-auto with the heel of your weak hand. Keep your hand high on the muzzle so you don't get mixed up with the recoil spring guide. You will notice that there's almost no tendency for the muzzle to rise until the barrel unlocks and stops. At that point, pushing any farther will force the muzzle upwards.

Push on the muzzle of the revolver the same way and you'll notice that if you want to move the barrel backwards at all, you can't do it without the muzzle rising.

Same thing happens when you shoot the guns but the recoil force does the pushing in that case.

 

[Walt Sherrill]

The fact that both the semi-auto AND the revolver are setting atop the hand, and the hand and arm acts as a fixed base against which the gun's recoil will press and, in effect, as a pivot point. A longer handle (high bore axis) on the gun will make the amount of pivot more noticeable. But most of THAT action happens after the bullet has left the barrel -- but it happens immediately, too.

Here's a YouTube video of a Beretta fired in three modes: without silencer, with a silencer, and with a silencer with slide locked shut (single shot).

You see barrel rise in all three examples. In the third example, THE BARREL AND SLIDE ARE FIXED AND DON'T MOVE, but the barrel still rises. In the last two of these cases, there's a heavy(?), long silencer on the gun, and we still see the barrel rise. What's making that barrel rise in that third case if the barrel and slide are FIXED and LOCKED to the frame?

https://www.youtube.com/watch?v=ShbLWQeZkzc

Other folks who seem to know more about this than I do say that when the round being fired is heavier -- and is moving more slowly -- but the same general force is being applied, the barrel rises higher before the bullet exists, because it takes the bullet LONGER to leave the barrel. It's a TIMING issue. The point of impact will be higher at relatively close distances (like 10 yds, 20 yds, etc.)

 

[TailGator]

What's making that barrel rise in that third case if the barrel and slide are FIXED and LOCKED to the frame?

I won't pretend to speak for JohnKSa, but I suspect his answer may be that locking the barrel and slide makes the whole assembly act more like a revolver, in that the forces of recoil are not absorbed by slide motion and barrel rise occurs for exactly the reasons you perceive - a force being transmitted at an axis above the point of support or rotation causes torque.

To me, the weakness of JohnKSa's argument is that the recoil force is partially transmitted to the pistol frame both by the compression of the spring and the friction of the slide. Muzzle rise can be argued to be lessened by the slide movement, but the forces transmitted by those two factors do not approach zero, and they begin before the bullet leaves the barrel, so it seems to me that they would affect the impact point on a vertical axis.

If I misunderstand or if I am oversimplifying, I expect to be educated.

 

[Limnophile]

A consistent and precise departure of 12 inches from the POA at 10 yards (115 minutes of angle) is not a shooter, sight picture, grip, range, or bullet weight issue; it's a gun problem, almost certainly incorrect sight height. Walt's post above with the math shows how to fix the problem.

Are HPs not test fired to ensure general accuracy before being shipped? Is the testfire target included with the gun? If so, what does it show?

 

[Walt Sherrill]

We MAY all be misunderstanding aspects of this phenomenon. There's science underlying it all, but I'm sure NOT a scientist.

Another video I found (but later lost, and couldn't find again) was of a guy shooting HOT .357 rounds through a long-barreled revolver. He showed the difference in points of impact when he was shooting from a rest, and when that rest included a heavy harness that kept the barrel from rising with recoil. A very obvious difference at short distances -- with the points of impact higher when the barrel wasn't wired down. (It was a very long-barreled gun, and that makes me think that the longer the barrel, the more noticeable the difference would be -- if moving more slowly for a GREATER distance matters...)

Other videos and forum photos show different points of impacts at the same distance with different loads, with the heavier loads typically hitting higher -- but there are strange exceptions in some of these that don't always make sense.

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[TunnelRat]

I think we lost the plot somewhere.

 

[JohnKSa]

You see barrel rise in all three examples.

To see the difference between an auto and a revolver, you would need to view the gun firing in very slow motion. The differences happen before the bullet leaves the muzzle which is a very short time interval. Looking at real-time videos won't show the difference.

Did you try the experiment I suggested? It really illustrates the difference in a way that's very easy to see and understand.

Other folks who seem to know more about this than I do say that when the round being fired is heavier -- and is moving more slowly -- but the same general force is being applied, the barrel rises higher before the bullet exits, because it takes the bullet LONGER to leave the barrel. It's a TIMING issue. The point of impact will be higher at relatively close distances (like 10 yds, 20 yds, etc.)

That is all precisely correct IF significant muzzle rise occurs BEFORE the bullet leaves the barrel.

I highlighted a section in the quote. It is only correct if there's significant muzzle rise while the bullet is still in the barrel. If the barrel doesn't rise before the bullet exits there's no trajectory difference and it doesn't matter how long the bullet is in the bore. There's ONLY a trajectory difference if the muzzle rises BEFORE the bullet exits.

The issue is that in a locked breech semi-auto, there is very little muzzle rise before the bullet leaves the bore. That is because the barrel recoils nearly straight backwards until it hits the end of travel and is stopped. THEN muzzle rise begins but it doesn't affect the bullet's trajectory significantly because the bullet is out of the bore before any significant muzzle rise occurs.

Revolver
1. Bullet starts moving/recoil begins/muzzle rise begins because the barrel can not recoil straight back and the entire gun must move as a single unit.
2. Bullet travels down the bore and exits with muzzle pointing higher than it was when the bullet started moving.

Locked breech semi-auto
1. Bullet starts moving/recoil begins/no significant muzzle rise because the barrel can recoil straight back riding on the frame rails.
2. Bullet travels down the bore and exits with muzzle pointing virtually the same elevation as it was when the bullet started moving.
3. After the bullet is gone, the barrel is stopped and significant recoil force is transferred to the frame--muzzle rise begins.

Note the difference in where the muzzle rise occurs. In a revolver, it begins as soon as the bullet starts moving. In a typical locked breech semi-auto it doesn't really start until the bullet is already out of the bore.

I think we lost the plot somewhere.

Well, sorta. We're talking about what will and won't affect elevation on the target.

 

[L-2]

Since none of us are there with the OP, someone else will need to be there, hopefully, an experienced shooter. You know, the type of person who can pick up any handgun and be very accurate.

Have that person shoot the HK. Then have them watch you (the OP) shoot. If they're really observant, they can spot what's going on. Since many cell phones can now do video, they can even video you to spot any problems in stance, breathing, trigger press, grip. This is what an instructor would be doing.

As a comparison, do the same things but with the SIGs with which you're not having any problems. Spot any differences in shooting technique.

 

[TunnelRat]

Well, sorta. We're talking about what will and won't affect elevation on the target.

It started that way, but I don't think a comparison between revolvers and semiautomatics in terms of recoil forces and when they impact the shooter is going to help odugrad. I think trying different ammo and/or a slightly higher sight picture will show results, and if not it does look like there are different height front sights available. I get the origins of the academic discussion, I just think it's started to drift noticeably and may be more technical than necessary now. Hopefully Odugrad gets a chance to hit the range and reports back.

 

[Walt Sherrill]

Did you try the experiment I suggested? It really illustrates the difference in a way that's very easy to see and understand.

I'd argue that your experiment is a different exercise. You're pushing BACK on the slide, rather than having the slide powered to the rear by a bullet moving forward. No equal but opposite reactions being demonstrated, there. And while the semi-auto's barrel is moving to the rear and a revolver's barrel is fixed, the moving slide and locked barrel ARE pressing against the frame through the recoil spring. The effect of that interaction, while modest before the bullet exits, does exist. (Is it non-trivial-enough to affect the POI? The way to find out is to lock the slide and fire it. I haven't found an example of that, yet.)

It may be that the visible rise we see in all three versions of the Beretta (1 with no silencer, 2 with silencer, and 3 with silencer and LOCKED slide) occurs AFTER the bullet has left the barrel. It would be hard to see in even the best slow-motion videography. We don't have any data about the POI of the rounds fired by the Beretta in those three modes. A view of the targets from all three options would be informative – for that could show the consequences of a locked slide. Total recoil is noticeably different -- but recoil after the bullet has left the barrel isn't of interest.

On this and other forums there are a number of discussions with targets shown, and videos on line showing how different rounds of different weights have noticeably different points of impact. Generally, the heavier bullets tend to hit higher but, and it's a BIG “but,” we don't know that the only difference between the rounds was bullet weight... So without more details, they aren't evidence.

None of this really addresses how a heavier bullet affects point of impact when fired in a semi-auto when most of the other variables are kept similar.

Your explanation makes sense, but I don't find it totally satisfying. Mine doesn't satisfy you. I'll just have to wait until I find more convincing evidence, one way or the other. If anyone finds anything that clarifies this topic, please post it. I'll try to do that if I find any of value -- as a new topic...

 

[TailGator]

Did you try the experiment I suggested?

I did. It seemed to me that I felt upward torque with the semi - less than the revolver, but not zero. Wouldn't that be because the recoil spring is being compressed and it is a bit above the center of my hand providing the resistance? I don't see how we can ignore the force on the RSA. I grant that it is lower than the barrel, but it still is above the axis of my hand, wrist, and arm.

 

[JohnKSa]

You're pushing BACK on the slide, rather than having the slide powered to the rear by a bullet moving forward.

The bullet pushes back on the slide in EXACTLY the same manner as your hand but much more abruptly.

I did. It seemed to me that I felt upward torque with the semi - less than the revolver, but not zero.

There will be some because the recoil spring weakly couples the slide/barrel to the frame. But there's very little because the recoil spring's effect is pretty weak early in recoil cycle and because the recoil force is applied very abruptly.

The very obvious thing the experiment shows is the difference between the two. Any recoil causes the revolver's muzzle to rise immediately while it's possible to push the slide back on a semi-auto without the muzzle rising at all until the barrel unlocks.

The way to find out is to lock the slide and fire it.

That's one way.

Another way to see the difference is to do some careful diagrams that show the boreline vs the sightline in a sampling of autopistols and revolvers. It immediately becomes clear that there's very obvious compensation by the sights for the muzzle rise in a revolver and virtually none in autopistols.

None of this really addresses how a heavier bullet affects point of impact when fired in a semi-auto when most of the other variables are kept similar.

The answer is that there's very little effect because there's very little muzzle rise before the bullet exits.

By design, a locked breech design is designed not to unlock until the bullet is out of the barrel. Therefore the slide and barrel recoil virtually straight back with no significant muzzle rise the entire time the bullet is in the barrel.

It started that way, but I don't think a comparison between revolvers and semiautomatics in terms of recoil forces and when they impact the shooter is going to help odugrad.

Perhaps not, but he's not the only person reading the thread. Also, the last time he logged on to TFL was 2 days before my first post.

 

[JDBerg]

I've had three HK pistols and I still have the P30 9mm and the HK45. All of these guns shot right on top of the sights out to 25 yds. regardless of what they were loaded with. But yours is so far off that I would waste no time to get on the phone with HK CS to make arrangements to send that pistol back for factory service. Putting it as nicely and as mildly as I can, HK CS is not exactly my favorite bunch to deal with, so I'd be very interested to know how they will address this problem for you.