38spl 125gr JHP shooting high.

I'm not 100% sure, but I think the sights are calibrated for 158 gr loads. So anything lighter and faster is going to shoot high. I never would've guessed it would make that big of a difference at pistol target distances, but it sure seems to.
This is just what I've observed with my revolvers, and what I've read.

Are you aiming 6 O' clock or dead center? My S&W 637 shoots to POA when aimed 6 O' Clock, my Colt 1911 Government shoots to POA when held Dead Center. Heavy bullets generally shoot higher at SD/HD handgun distances due to more recoil/muzzle rise/barrel dwell. Same is true with similar weight bullets when one is loader hotter than the other. That is why most fixed sighted guns are regulated for specific weight bullets generating specific velocities. This is also why folks shoot different weights/velocities till they find something that shoots to POA.

My guess is that the +p Golden Sabres are generating more recoil than your reloads, thus impacting the target higher. Nature of the beast.

My 642 and 442s shoot pretty much dead on with 125 grain +p Golden Sabers. It's my preferred load with my j frames. As mentioned, it could be you're accustomed to a particular POA with your reloads and the POA for the Golden Sabers is different. In my guns they shoot to the top of the front sight.

That's the only headache (IMO) with fixed-sight revolvers; you can't change the sight picture by merely adjusting the sights. Instead you have to self-regulate the sights when you change loads. (Or in rare cases return a gun to the manufacturer for a fix if the barrel is aligned crooked, etc).

In your case it looks like either holding low with your standard sight picture, or burying your front sight down in the notch as you aim, will bring the impact point to where you are used to with the other ammo.

This is another good reason to buy sufficient defense-oriented ammo to shoot in your chosen defense guns. Besides finding a bullet that does what you want to (reliably expand, etc), you need to check for the ammo's function, your handgun's reliability with that ammo, and the impact point of the projectile on the target, before you trust the load with your life. At least you figured out the issue beforehand, now you can work to get the impact point back to where you want it.

Stay safe!

buck460XVR said:

Are you aiming 6 O' clock or dead center?

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Key question, because...

Ironicaintit said:

sights are calibrated for 158 gr loads.

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...this. Adjust accordingly.

The Airweight 642 with +P ammo isn't a whole lot of fun to shoot, that's for sure! I practice with wadcutters when shooting mine because I can shoot more rounds without every shot delivering hand-slapping recoil.

I do shoot my usual defensive ammo (Hornady +P Critical Defense) every once in a while to maintain my sight picture/point of impact memory with this gun. My gun shoots them pretty much POI, maybe a touch high at 15 yds.

Federal HST bullets in all of their offered calibers seem to have a good rep, they aren't a bad choice for SD ammo at all.

I find that my revolvers shoot low with lighter bullets. I guess the load or charge has much to do with the time the bullet is in the barrel and how well the recoil is restrained by the shooter.

What I think I know about pistols, bullet weights, and velocities: We tend to think it is the external ballistics of the round that make the difference in the point of impact between different loads. Instead, it is the amount that the pistol recoils in the hand before the bullet leaves the barrel that makes the big difference.

Given the same chamber pressure, a heavy bullet leaves the barrel more slowly than a lighter bullet. This gives the gun more time to rotate UP in the hand before the bullet gets out, and means a higher point of impact for the heavy bullet.

In ohihunter2014's example, we have two bullets of essentially the same weight, but with different chamber pressure. Although the higher pressure gets the bullet out of the barrel faster, it is (apparently) also causing the gun to recoil even more before the bullet emerges. I have to say, this is not what I would have predicted based on my understanding above. Do I not know what I what I thought I knew?

Monac said:

What I think I know about pistols, bullet weights, and velocities: We tend to think it is the external ballistics of the round that make the difference in the point of impact between different loads. Instead, it is the amount that the pistol recoils in the hand before the bullet leaves the barrel that makes the big difference.

Given the same chamber pressure, a heavy bullet leaves the barrel more slowly than a lighter bullet. This gives the gun more time to rotate UP in the hand before the bullet gets out, and means a higher point of impact for the heavy bullet.

In ohihunter2014's example, we have two bullets of essentially the same weight, but with different chamber pressure. Although the higher pressure gets the bullet out of the barrel faster, it is (apparently) also causing the gun to recoil even more before the bullet emerges. I have to say, this is not what I would have predicted based on my understanding above. Do I not know what I what I thought I knew?

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You get the general idea, pretty much what I said in my above post...

Heavy bullets generally shoot higher at SD/HD handgun distances due to more recoil/muzzle rise/barrel dwell. Same is true with similar weight bullets when one is loader hotter than the other.

My guess is that the +p Golden Sabres are generating more recoil than your reloads, thus impacting the target higher. Nature of the beast.

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Thanks, buck460XVR!

Monac said:

Given the same chamber pressure, a heavy bullet leaves the barrel more slowly than a lighter bullet. This gives the gun more time to rotate UP in the hand before the bullet gets out, and means a higher point of impact for the heavy bullet.

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Kind of. Remember that the gun & muzzle recoil with some ammo-dependent velocity, too. Yes, the slower bullet travels down the barrel slower, but the velocity of the muzzle rise is correspondingly slower too, so for any given bullet weight (and gun mass and barrel length), the muzzle will rise the same distance, regardless of bullet velocity. IOW, a heavy bullet hits higher because it's heavier, not because it's slower.



EDIT: To be clear, it's actually the total ejecta mass that matters, not merely the bullet mass. A faster bullet of the same mass has more powder behind it, so depending on how much powder, and how light the gun, the faster bullet could hit higher - but again, it's a mass issue. My guess is the OP's +P ammo is hitting higher because of more powder and a relatively light gun.

when shooting my S&W 637 .38 spl Airweight snub I find that the Remington 124 gr GS shoot right to top of sight when the top of the front sight is lined up evenly across the top of the rear notch at 15 to 25 yds. My 158gr hand loads generally shoot 3" to 4" higher.

If you are shooting higher you should try increasing your grip so you don't break your wrist up during recoil and provide a more solid base of hand and arm to resist the upward flip of the handgun.

MrBorland said:

Kind of. Remember that the gun & muzzle recoil with some ammo-dependent velocity, too. Yes, the slower bullet travels down the barrel slower, but the velocity of the muzzle rise is correspondingly slower too, so for any given bullet weight (and gun mass and barrel length), the muzzle will rise the same distance, regardless of bullet velocity. IOW, a heavy bullet hits higher because it's heavier, not because it's slower.



EDIT: To be clear, it's actually the total ejecta mass that matters, not merely the bullet mass. A faster bullet of the same mass has more powder behind it, so depending on how much powder, and how light the gun, the faster bullet could hit higher - but again, it's a mass issue. My guess is the OP's +P ammo is hitting higher because of more powder and a relatively light gun.

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at first read, this didn't seem quite right. so, today i went out shooting to see for myself:



the 357 magnum shows a small rise in poi with the slower load. but, the 44 magnum and the heavy bullet shows a marked rise in poi with the slower load. as this is only ten yards, i would think the rise difference would be greater at distance until the flatter trajectory of the faster bullet would "catch up" with the slower bullet.

i actually learned a bunch from this. one, don't run a hollow based bullet at 1300 fps (accuracy sucks and i'm probably going to be scrubbing lead out of the barrel tonight). two, the 300 grain bullet @ 1400 fps is still difficult to shoot accurately. three, the 300 grain bullet @ 1000 fps out of the heavy super blackhawk is a joy to shoot.

later,

murf

p.s. the point of aim for all groups is at the center of the cross.

ohihunter2014 said:

I was given about 25 124gr +p golden sabers for my S&W 642 and tested their accuracy last night and compared to my 124gr FN bullets they shot very high. High as if I was to shoot a human target in the chest it would hit them in the neck. My 124gr FN shoots right where I aim but these are about 6-8'' high all the time.

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I have a Colt Cobra revolver, circa 1968, that shoots very high (a foot or more) @ 25 yards with Hornady 158 gr XTP ammunition. I realize that 25 yards is much farther than what a snub-nosed revolver would generally be expected to be effective at but I like to sight most of my handguns in at that range.

Opinions so far in this thread seem to be mixed as to whether lighter or heavier bullets will bring the poi down (for a self-defense handgun, I prefer a "dead center" hold as opposed to a 6:00 or "Kentucky windage" hold) but, in terms of "physics" at least, MrBorland's explanation seems to make the most sense. Adding material to the top of the front sight doesn't seem practical to me so, like the op, I'm interested in all suggestions and advice as to the best way to lower the poi to conform closer (if not necessarily exactly) to the poa.

MrBorland said:

Kind of. Remember that the gun & muzzle recoil with some ammo-dependent velocity, too. Yes, the slower bullet travels down the barrel slower, but the velocity of the muzzle rise is correspondingly slower too, so for any given bullet weight (and gun mass and barrel length), the muzzle will rise the same distance, regardless of bullet velocity. IOW, a heavy bullet hits higher because it's heavier, not because it's slower.

EDIT: To be clear, it's actually the total ejecta mass that matters, not merely the bullet mass. A faster bullet of the same mass has more powder behind it, so depending on how much powder, and how light the gun, the faster bullet could hit higher - but again, it's a mass issue. My guess is the OP's +P ammo is hitting higher because of more powder and a relatively light gun.

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This subject gets very confusing very fast. I was assuming that all standard velocity 38 Special loads, for example, had the same powder charge. I guess I also assumed that the weight of the powder charge was negligible compared to that of the bullet, so that the "total ejecta mass" did not differ with anything besides bullet weight.

What I do not understand is how "a heavy bullet hits higher because it's heavier, not because it's slower". I can think of only three factors where the bullet weight affects the point of impact, given that the energy imparted to the bullet by the powder charge is equal:

1) The amount the gun recoils in the hand before the bullet emerges from the muzzle. Given the same gun, this would seem to be greater for the heavier bullet because a) it takes longer to emerge from the muzzle, and b) in my experience, given that the load is of the same class (like standard velocity 38 Special) a heavier bullet has greater felt recoil. (Perhaps here is where I am making a mistake.)

2) The heavy bullet, at the lower velocity imparted to it by the fixed powder charge, takes longer to fly to the target. This gives the force of gravity more time to act on it. If the gun is aimed in exactly the same manner as for the lighter, faster, bullet, it will drop more on the way to the target and have a lower point of impact. (I may have this wrong too, of course, but if so I would like to know. When I first began to shoot a pistol well enough to see the difference between points of impact of groups, the fact that heavy loads did NOT shoot lower, which is what I expected, is what made me learn about this subject.

3) The heavier bullet has greater "sectional density" than a lighter bullet of the same caliber, and therefore does not slow down as much due to air resistance on the way to the target. This would help counteract factor 2 above. "Sectional density" is best understood as the way two objects of the same size but different weights - like a tennis ball ball and a regulation baseball - lose velocity differently. The heavier object has more momentum but the same air drag as the lighter one, and therefore loses velocity more slowly. I think I have this one right, so it's probably the trap.

I am sorry to belabor this point, but I would like to understand how I am wrong about it, if I am wrong. I do not understand the phrase "a heavy bullet hits higher because it's heavier, not because it's slower".

Nor do I understand the phrase"for any given bullet weight (and gun mass and barrel length), the muzzle will rise the same distance, regardless of bullet velocity." It either does not make sense, or it does not meet the condition I made about the powder charge being constant.

As I said, I thought the reason for the heavier bullet having a higher point of impact was the greater amount of recoil in the hand before the bullet emerges from the muzzle, (assuming that the fixed powder charges gives it a lower velocity, but everything else being equal). If it is not, what is? I would like to understand this. Thanks!

Monac said:

What I do not understand is how "a heavy bullet hits higher because it's heavier, not because it's slower".

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Sorry for the delayed reply.

As I wrote earlier, the slower bullet travels down the barrel slower, but the velocity of the muzzle rise is correspondingly slower too, so for any given bullet weight (and gun mass and barrel length), the muzzle will rise the same distance, regardless of bullet velocity.

If it's confusing, let's consider an example...a 4" 42oz S&W 686 firing 158gr and 125 grain bullets, at both standard velocity (750fps) and magnum velocity (1200fps). Dump the data into a recoil calculator (since we're not considering the effects of different powder mass, assume 6gr of powder for all loads), and check out the recoil velocity in FPS. It's correspondingly lower for the slower rounds.

Now use the approximate barrel dwell time to calculate the distance the gun travels while the bullet's in the barrel. You'll see there's more time to travel, but the velocity is lower, so the net distance is the same for the fast and slow round for both the 125 and 158gr bullet. You'll also see the gun travels farther when shooting the heavier bullet, which is why a heavier bullet hits higher, and why it's because it's heavier, and not because it's faster or slower.

158gr bullet:
..................fps......dwell time (msec).......recoil velocity (fps)..........recoil distance (inches)
Fast.........1200............0.28.........................11.7.....................................0.04 (=0.00028 x 11.7 x 12)
Slow.........750.............0.44...........................7.8.....................................0.04

125gr bullet:
..................fps......dwell time (msec).......recoil velocity (fps)..........recoil distance (inches)
Fast.........1200............0.28...........................9.5.....................................0.03
Slow.........750.............0.44...........................6.4.....................................0.03



EDIT: As I noted, for simplicity, and to look solely at bullet weight, I ignored differences in powder charge in the above example. For any particular bullet, though, the faster bullet will obviously have more powder behind it, so the mass of the ejecta (bullet + powder) is greater than that of the slower bullet, and the bullet will hit higher. IOW, a fast 125 ought to hit higher than a slow 125, but again, it's not because of the velocity and bullet dwell time, per se, but because of mass (the total mass of the fast 158 being greater).

MrBorland said:

Sorry for the delayed reply.

As I wrote earlier, the slower bullet travels down the barrel slower, but the velocity of the muzzle rise is correspondingly slower too, so for any given bullet weight (and gun mass and barrel length), the muzzle will rise the same distance, regardless of bullet velocity.

If it's confusing, let's consider an example...a 4" 42oz S&W 686 firing 158gr and 125 grain bullets, at both standard velocity (750fps) and magnum velocity (1200fps). Dump the data into a recoil calculator (since we're not considering the effects of different powder mass, assume 6gr of powder for all loads), and check out the recoil velocity in FPS. It's correspondingly lower for the slower rounds.

Now use the approximate barrel dwell time to calculate the distance the gun travels while the bullet's in the barrel. You'll see there's more time to travel, but the velocity is lower, so the net distance is the same for the fast and slow round for both the 125 and 158gr bullet. You'll also see the gun travels farther when shooting the heavier bullet, which is why a heavier bullet hits higher, and why it's because it's heavier, and not because it's faster or slower.

158gr bullet:
..................fps......dwell time (msec).......recoil velocity (fps)..........recoil distance (inches)
Fast.........1200............0.28.........................11.7.....................................0.04 (=0.00028 x 11.7 x 12)
Slow.........750.............0.44...........................7.8.....................................0.04

125gr bullet:
..................fps......dwell time (msec).......recoil velocity (fps)..........recoil distance (inches)
Fast.........1200............0.28...........................9.5.....................................0.03
Slow.........750.............0.44...........................6.4.....................................0.03



EDIT: As I noted, for simplicity, and to look solely at bullet weight, I ignored differences in powder charge in the above example. For any particular bullet, though, the faster bullet will obviously have more powder behind it, so the mass of the ejecta (bullet + powder) is greater than that of the slower bullet, and the bullet will hit higher. IOW, a fast 125 ought to hit higher than a slow 125, but again, it's not because of the velocity and bullet dwell time, per se, but because of mass (the total mass of the fast 158 being greater).

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i was trying to be nice in my last post. i ran a test and disproved your statement that muzzle rise is the same for different velocities with the same bullet/gun combo. so, that statement is wrong.

muzzle rise is caused by the acceleration of the bullet down the barrel, not the acceleration of the powder "ejecta". powder "ejecta", while it is in the barrel is called pressure and has a net force of zero. so, while the bullet is traveling down the barrel, the only recoil is from the bullet acceleration. so, "ejecta" having an affect on muzzle rise before the bullet exits the barrel is also wrong.

fwiw, after the bullet leaves the barrel, the "ejecta" will increase recoil because the "pressure" now is only pushing back on the gun and not forward on the base of the bullet. but, this is irrelevant to this discussion.

this seemingly simple idea of the affects of velocity and mass on muzzle rise is, actually, quite complex. everything affects everything else. the only way to find out is to shoot the gun and see the holes on the paper.

murf

murf said:

i was trying to be nice in my last post. i ran a test and disproved your statement that muzzle rise is the same for different velocities with the same bullet/gun combo

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Neither escaped my attention. Thanks for posting .

At any rate, only half of your test "disproved" my statement - the other half supported it, since both your slow and fast 148gr HBWC loads printed pretty much to the same spot (well within shooter error). FWIW, I've tested different loads in the same bullet weight and found they typically print to very similar POAs. YMMV.

I'll also point out that the above is the theoretical description, and really applicable when you take the shooter out of the equation, so the valid test is a Ransom rest. Your offhand results are a bit inconclusive, which supports this.

murf said:

this seemingly simple idea of the affects of velocity and mass on muzzle rise is, actually, quite complex.

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I agree it's more complex than my admittedly simple description. But the basic physics says it's also velocity-independent, so the common "time in the barrel" assumption & explanation just doesn't jive with the basic physics (or my personal experience).

MrBorland said:

Neither escaped my attention. Thanks for posting .

At any rate, only half of your test "disproved" my statement - the other half supported it, since both your slow and fast 148gr HBWC loads printed pretty much to the same spot (well within shooter error). FWIW, I've tested different loads in the same bullet weight and found they typically print to very similar POAs. YMMV.

I'll also point out that the above is the theoretical description, and really applicable when you take the shooter out of the equation, so the valid test is a Ransom rest. Your offhand results are a bit inconclusive, which supports this.



I agree it's more complex than my admittedly simple description. But the basic physics says it's also velocity-independent, so the common "time in the barrel" assumption & explanation just doesn't jive with the basic physics (or my personal experience).

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nice try. you are still wrong. and those reading this thread need to know this because most here put a lot of importance in your posts.

thank you for acknowledging the complexity of this topic.

also, you need to show the physics instead of just saying so. show us how linear acceleration is equal to angular acceleration in this scenario.

murf

like post 2, I think most 38 revolvers are setup for 158 at around 800, or 148 at around 750. More kick, higher hits.

Thank you for your kind reply, MrBorland. I will concentrate on understanding it rather than saying anything else. If I understand it now, you are saying that, everything else being equal*, increasing the bullet weight increases recoil travel, which in a pistol is partly expressed as muzzle rise, and that is why heavier bullets hit higher. No reference to the time the bullet spends in the barrel is necessary.

If I continue to misunderstand it is not your fault, and I will continue to study your reply.

*except for the fact that increasing the bullet weight while keeping the powder charge constant means the bullet velocity decreases.