Such a thing as pistol harmonics?

S

stagpanther

New member
I've been reloading for rifles and handguns for quite some time--and usually can find the "sweet spot" for rifle cartridges eventually. There is the popular notion of "barrel harmonics" that makes one cartridge combination work better than others.

I usually develop handgun cartridges the same way--but have no idea if the same Barrel harmonics comes together for a handgun load as well. Truth is, I'm pretty bad with handguns in general--and when one group turns out to be markedly better than all the rest--I figure it was mostly because I was lucky enough to hold the gun steady enough through the trigger pull.

Comments?
 
It isn't really harmonics. That was speculation by folks who didn't know better. The harmonic ringing of a barrel occurs after the bullet leaves. The muzzle deflection that occurs when the bullet is still on its way to the muzzle is caused by recoil moment bending and pressure distortion, as demonstrated by former Lawrence Livermore National Laboratories engineer, Varmint Al.

The main thing that allows the barrel deflection is that it isn't rigid enough to prevent it. But as a barrel gets shorter, it gets more rigid. I have not seen signs in handguns that would clearly indicate that such deflections as may occur in the shorter shape affects the group as much as normal noise in the shooter-gun-targets system.
 
It seems pretty common in handguns to not have complete combustion of propellent prior to bullet leaving the muzzle. I guess a better way to ask my question is is there a better way to go about seeking the best/most accurate load for a handgun than what is typically used in developing rifle loads? Part of my problem is that my own "induced technique inaccuracy" in shooting makes it hard for me to see marked differences in the groups. I know--part of the answer is practice more.:o
 
Actual harmonics would depend on the pistol.
I'm sure it's an issue encountered by some T/C shooters.
Maybe some of the really long barreled revolvers.

When i'm doing load development for my 1911, and PPS i use a decent rest.
With the 185gr LSWC out of the 45, fast burning powders like Red Dot work well.
Add a jacket and some velocity for defensive ammo and powders like Silhouette get the nod.
 
It might depend on what gun/platform you're using, as well as what bullets you use, and your method. With handguns, the nod usually goes to the Ransom Rest, but since few shooters have them, shooting of a bench with a sturdy rest is the best method.

The bullets can make a huge difference in accuracy, like a 2-, 3-, or 4-fold difference in group size. Can you give us some details on your gun and loads, and additional information on how many shots per group, etc.?
 
I do a lot of things. Bullet is most important. Some shoot better in different guns.

I was a bullet caster for 20 years. Style and fit are important.

I choose a bullet I hope will work and test. I load different charges and shoot for groups. I have expectations for different guns.

If I don't see even close to what I am after, I try a different bullet

If one shows more potentel than the rest, I mess with OAL unless its a revolver
.
After some testig I found out my latest 1911 9 mm likes FMJ better than HAP. It does not like coated lead at all until I get to 147 grain. I also found out it likes max charges of powder. As I worked up, groups got smaller.

So In the end, I found 115 FMJ over a max charge of WW231 gave me 1100 fps with an SD of 6 and under 1.5" @ 25 yards. A max charge of Unique Gave me just over 1" @ 1225 FPS.

I did find a load of 115 HAP that shoots well out of my other 1911 9mm also shoots well in this one. 115 HAP over 4.0 tite group. I wanted a light load, so I did from 3.5 to max in .2 incraments shooting 5 shot groups. 4.0 stood out clearly being the most accurate. Its 975 in my 4" and 1025 in my 5"

I have yet to see a revolver that will not shoot a HBWC with 2.7 to 3.0 Bullseye.

David
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Stagpanther,

With handguns of either the rotary or linear fed kind, I've found getting the gun accurized, followed by bullet choice followed by charge choice does the most for accuracy. Beyond that, the specific gun needs to be known to do much better. For example, in a 1911, seating cast bullets out so the cartridge seat is bullet contact with the lands has cut target load group size by up to 40% for me. However, in the same gun, it made no difference to how jacketed bullets performed. But in a revolver, that's useless information regardless of bullet type. In a revolver, getting all the chamber throats to a uniform diameter at least 0.0015" over groove diameter and timed to line chambers up with the center of the bore seemed to be most important to mechanical accuracy with cast bullets. Good trigger work has proven to be very important to the operator being able to sandbag good groups.

A general observation I would make is that, with the exception of single-shot handguns, a handgun that will group 2 MOA 50 yards is considered the match accuracy equivalent of a rifle that will group ½ MOA at 100 yards. About a 4:1 accuracy expectation from self-loading and revolving handguns for match shooting. Mostly, you can't see the variation caused by mixed brass, exact bullet jump and other factors that affect load tuning in a rifle in a 2 MOA group, so a lot of that detail just can't be usefully applied to pistol and revolver loads. You simply get a lot more mileage out of the larger load factors, like bullet choice. Even in an exceptionally tight shooting gun like my Redhawk, I can't see signs of the flat spots in an Audette ladder that you get with a rifle, as revealed by Varmint Al's animation showing the exaggerated barrel bending in a rifle with a barrel tuner. I think the shorter barrel is just too rigid to bend appreciably under the upswing caused by recoil. Too many other movement factors are dominating the precision limits. Keep in mind the moment of inertia for a rotation on a horizontal axis perpendicular to the bore axis, where the length of the barrel is the radius of the recoil elevated mass, will go up as the square of the length of that radius (the length of the barrel). So a 4-inch revolver barrel, subjected to the same amount of recoil lifting force as a 24" rifle barrel with the same OD and same bore dimensions would see only 1/36 of the barrel bending at the anchored receiver end that 24-inch barrel would. That explains a lot about why the muzzle swing is MIA from group analysis for the revolver.
 
Great stuff guys, thanks for the useful advice.

What do I shoot? A pretty wide spread of types--ruger Blackhawks in 41 and 44 mag, ruger lc9s carry pistol, glock 20 in 10mm and 9x 25 Dillon, colt 1911 in 38 super. If I can get a group of 4" at 20 yds I'm having a very good day--though that's using typical stock drop in the bucket irons.
 
stagpanther said:
Great stuff guys, thanks for the useful advice.

What do I shoot? A pretty wide spread of types--ruger Blackhawks in 41 and 44 mag, ruger lc9s carry pistol, glock 20 in 10mm and 9x 25 Dillon, colt 1911 in 38 super. If I can get a group of 4" at 20 yds I'm having a very good day--though that's using typical stock drop in the bucket irons.
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So you're not testing accuracy at all? You're just shooting and calling it a good day if you get a 4" group.

Not much we can do under those conditions.
 
Unclenick said:
It isn't really harmonics. That was speculation by folks who didn't know better. The harmonic ringing of a barrel occurs after the bullet leaves. The muzzle deflection that occurs when the bullet is still on its way to the muzzle is caused by recoil moment bending and pressure distortion, as demonstrated by former Lawrence Livermore National Laboratories engineer, Varmint Al.
Click to expand...

Is this to say that the phenomenon commonly referred to as harmonics is misunderstood at to what is actually going on, or just called something that it is not?
By that I mean is what people are referring to as harmonics actually occurring or is it another phenomena altogether?
 
Nathan,

I'd say both. The barrel under pressure doesn't bend the same way it does after the bullet leaves. The bend of the muzzle is the same kind of bend you see if you crack a whip; a bend under an actively applied force (recoil and pressure). Note that it doesn't happen in a barrel mounted to recoil straight back into a machine rest. It's due to the recoil vector that causes muzzle rise and is due to the barrel line being above the point of support (buttstock on the shoulder). This is why bullpup rifle designs often lack muzzle rise and without that, don't get the bend. The point of impact is affected by the phase of the muzzle bend at which the bullet left the barrel, so it looks like the barrel was ringing rather than being cracked like a whip. For POI purposes it would be indistinguishable.

If you look at harmonic nodes that Al modeled, they do occur as damped ringing after the bullet has left the muzzle. But up to the moment the bullet leaves, the barrel is not ringing yet. It is, in effect, a different structure because of the pressure in it, and therefore, if you would ring it with pressure inside (bullet stuck in bore near the muzzle and breach perfectly sealed) it would ring at slightly different frequencies.

So, bottom line, it's a barrel bending-induced muzzle deflection and not harmonic ringing that causes the effect on POI that shooters see in an Audette ladder.
 
IN simplest terms, a gun barrel is a bar held at one end, and not held at the other. Strike the end that is held, and the far end moves.

Call it harmonics, whip, ringing, or any other term that applies, the effect is a constant. The AMOUNT of the effect varies, and can vary a lot.
 
Handgun barrels are too short for harmonics.
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I disagree. Length (and stiffness) only matter in the degree of movment, and the ease of recognizing and measuring it. Any solid, stuck at one end will transfer the vibration to the far end. All that differs is the degree.


The shooter can't hold a handgun still enough for it to matter anyway.
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Agree. Generally. But there are situations where the "harmonics" of a pistol barrel can matter. If possible, rest the pistol barrel on a solid object, and shoot. Repeat without the barrel rested and see the difference. Support the frame and not the barrel, and see the difference. There can be a difference. Sometimes a significant one.

Now, some pistols can't do this, because the barrel is enclosed in the slide, but others (like revolvers and some autos) can. Most guns show a tendency to shoot "away" from point of aim when the barrel is in contact with a solid object. Rest the stock, or the frame, or your hands on a solid object, its different harmonics then when the barrel itself is in contact with something when fired.

Again, it is most noticeable in rifles, but pistols do it, too. Just to a lesser degree.
 
Agree. Generally. But there are situations where the "harmonics" of a pistol barrel can matter. If possible, rest the pistol barrel on a solid object, and shoot. Repeat without the barrel rested and see the difference. Support the frame and not the barrel, and see the difference. There can be a difference. Sometimes a significant one.
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Yes!--this is what I've experienced--and in fact drove me to the original post.
 
When you rest a gun on something you change the recoil dynamics. Have someone stand to the side and observe how much muzzle flip you get, then change your support position and see if that doesn't change as well. I took a slow-motion YouTube video of a 460 S&W with Magnaporting being fired and marked it with lines so I could see, between the flash appearing at the barrel/cylinder gap and appearing at the ports, how much muzzle rise there was. It's small but real and since it is happening before the bullet clears the muzzle, it raises POI. Putting the same gun on a bag, so it starts with the weight of the gun plus downward pressure from the weight of your hands, you should not only add friction to the rearward recoil but reduce how much flip you get before the bullet clears the muzzle because of that downward pre-loading, tending to lower POI. Conversely, a rest that lets you grip the gun lower on the frame will tend to raise POI because that increases the moment arm the flip pivots around. Consistency is everything in pistol accuracy.
 
Sure there are barrel harmonics, but not enough to make any measurable differences in the short barrels of most pistols and revolvers. Even more so than rifles, powder charge variation is a contributor to larger SDs. While 1/10th of a grain might represent a change of say 0.1% MV in a rifle, that can be 2 or 3 percent in a pistol. Powders that are relatively slow (based on barrel length) and are burning longer than the dwell time of the bullet in the barrel typically produce higher SDs as well.
 
Sure there are barrel harmonics, but not enough to make any measurable differences in the short barrels of most pistols and revolvers. Even more so than rifles, powder charge variation is a contributor to larger SDs. While 1/10th of a grain might represent a change of say 0.1% MV in a rifle, that can be 2 or 3 percent in a pistol. Powders that are relatively slow (based on barrel length) and are burning longer than the dwell time of the bullet in the barrel typically produce higher SDs as well.
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Makes excellent sense--thanks for that.
 
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