TargetTalk

jliston48 wrote:...David N's posting on wind deflection contradicts my understanding of vectors. Surely the wind deflection on a moving body is proportional to the period of time it is exposed to the wind so a slower body would be deflected more than a faster one.

Sorry, no.

Wind drift and time of flight are not related, not at all. In the higher velocity ranges, they track each other and thus seem related but that's only true once you get above about 2300 feet per second.

Wind drift is a function of the rate of velocity loss. Transonic buffeting of the projectile starts kicking in at about 900 feet per second. That buffeting starts to make the projectile shed velocity more quickly than at lower speeds. This effect gets worse and worse well past the speed of sound, up to about 1400 feet per second. It then starts to taper off but isn't completely gone until about 2300 feet per second.

Thus, a projectile launched at 875 feet per second will drift a certain amount over a certain distance in a certain crosswind. Keep conditions the same and increase the speed of the projectile. Wind drift will get worse (sometimes, depending on the shooting sport, much worse) up to about 1400 feet per second. Once you get the projectile up to about 2300 feet per second, the wind drift figures will fall back to about where they were at 875.

At even higher velocities, the bullet completely outruns all transonic buffeting and it appears that time of flight and wind drift track perfectly with each other. Thus, many centerfire rifle shooters who never shoot anything at low velocities, when they are exposed to the whole concept that longer time of flight can equal less drift, find the whole idea so counterintuitive that they dismiss it. That's one reason that high-power rifle shooters have such problems at extended range. If you've ever talked to long range riflemen who use most modern cartridges, they'll often attest to the fact that the jump from 600 yards to 800 yards is no big deal. However, going from 800 to 900 is much worse and going from 900 to 1000, things just seem to go to hell. The reason is because their bullets, even though they are staying nominally supersonic, are dropping into that 1700-1400 feet per second range where wind drift just seems to whack your performance so much harder than it should. In many real world cases, bullets fired from high-power rifles will drift more in the wind between 800 and 1000 yards than they did all the way from the muzzle to 800.

Take any projectile and plug it into any ballistics computer program. (Here's a commonly used one: http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi ) Check the wind drift in 100 feet per second intervals from 900 to 2300. It seems weird but it's well documented.

The only people that seem to be aware of it, as groups, are black powder cartridge rifle shooters and pistol silhouette shooters. Both those groups of competitors shoot firearms that force them to deal with those velocity ranges and both groups tend to curse the laws of physics with some regularity.

If someone could recommend some brands/types of .22LR that clock 850-900 feet per second out of a pistol-length barrel, I'd be interested. Even the "sub-sonic" stuff that I've tried runs too fast (according to published specs) to *truly* minimize wind drift. (Edited to add - I really need to break out one of my chronographs and do some testing. If the velocities on the boxes are from testing in rifles, there may be any number of types of ammo out there that shoot close to the ideal for fighting the wind, i.e. ~875 feet per second. I just don't have a place where I can set up a chrono right now.)

As an aside, I have seriously considered building a silhouette pistol with an extremely fast-twist barrel specifically to use that Aguila SSS .22LR ammunition that uses 60-grain bullets. The velocity should be right for cheating the wind and the extra bullet weight would make them suitable for knocking down field pistol targets. I wonder if anyone has ever experimented with the stuff in a re-barreled free pistol? After all, Pac-Nor does make 1-in-6" twist barrel blanks for .22 rimfire. Just a thought...

Hey, we are talking Free pistol here. Most of the finer points of performance don't matter a rat's until you can shoot above a 560.
Some of the things I have learnt are...
1/ There is no correlation between cost of ammo and performance. (I once shot a national record with ammo that was $3.40 a box)
2/ The biggest wind effect is your own stance, holding a pistol one handed in a wind has a vastly bigger effect on impact that any ballistic trait.
3/ Find a ammo of a Standard velocity that is plentiful and available locally (subsonic from your pistol) that feeds well, extracts easily, has low MAD on a chrono and just test it, Nearly all ammo's from a free pistol will hold the ten ring (some a little better than others).
4/ When testing. hand fire some rounds and note the different feel of each ammo. Some ammo's have much better feedback to the shooter than others and are better to work with. Some have a hard or soft feel.

David M wrote:Hey, we are talking Free pistol here. Most of the finer points of performance don't matter a rat's until you can shoot above a 560.
Some of the things I have learnt are...
1/ There is no correlation between cost of ammo and performance. (I once shot a national record with ammo that was $3.40 a box)
2/ The biggest wind effect is your own stance, holding a pistol one handed in a wind has a vastly bigger effect on impact that any ballistic trait.
3/ Find a ammo of a Standard velocity that is plentiful and available locally (subsonic from your pistol) that feeds well, extracts easily, has low MAD on a chrono and just test it, Nearly all ammo's from a free pistol will hold the ten ring (some a little better than others).
4/ When testing. hand fire some rounds and note the different feel of each ammo. Some ammo's have much better feedback to the shooter than others and are better to work with. Some have a hard or soft feel.

Fantastic response and pretty much what I was looking for. I'll start out by shooting what I have and see how it goes.

Many Thanks,

Joel

David M wrote:Hey, we are talking Free pistol here.

Quite right. jliston48 had requested information and I provided it but I used examples beyond the scope of this sub-forum. My apologies.

Is there any correlation between velocity and how forgiving it is. Air pistol is so criticle with trigger controll because the pellet is doing less than 600fps. how much quicker do you need to go before the time in the barrel doesnt matter. I have access to millions of 22 shorts that I could use to train with but I always thought it would make it harder to shoot

One of the issues is recoil, which will go up with velocity. Physics says the pistol WILL begin to move before the bullet leaves the barrel. As long as your hold is consistent, the amount it moves will be the same & you can dial it out with your sights. If your hold is not 100% the same every time, higher recoil will magnify this and your groups will grow.

So, higher velocity = more recoil = less forgiving.

I never thought of that. So there is 2 ways that affect how forgiving the velocity will be. Firstly lower velocity will be more forgiving than higher velocity for inconsistency in your hold and secondly, higher velocity eg rifle standard velocity will .br more forgiving to mistakes eg things that dislodge your sights.

I have a real problem in that my TOZ shoots Federal UM-1 better than any other ammo.....and I only have a brick left!

Rover wrote:I have a real problem in that my TOZ shoots Federal UM-1 better than any other ammo.....and I only have a brick left!

Ah, Yes! In the world of matching ammo to firearm - ain't it always the way?

Rover wrote:I have a real problem in that my TOZ shoots Federal UM-1 better than any other ammo.....and I only have a brick left!

hmm Id better actually test the new stuff. I had tested this in my toz which averaged 5mm for 10 shots which was better than tenex however I havent tested the new gold medal I hadnt realised the old stuff was a different designate. I wish you could still buy this

Gwhite wrote:One of the issues is recoil, which will go up with velocity. Physics says the pistol WILL begin to move before the bullet leaves the barrel. As long as your hold is consistent, the amount it moves will be the same & you can dial it out with your sights. If your hold is not 100% the same every time, higher recoil will magnify this and your groups will grow.

So, higher velocity = more recoil = less forgiving.

Physics says the gun will move, correct but the direction of travel of the gun will be in a line opposite to the direction of travel of the bullet. I.e straight back. It is only when that travel is impeded that it will go in a different direction - typically upwards, pivoted around the hand/thumb area.

In the real world the question is at what point is the bullet deflected (if at all) by the change in recoil direction and by how much. My suspicions are that any changes will be negligible to the POI but I have no idea how to calculate that or prove it.

Rob.

While I shoot bullseye and not free pistol, I have done quite a bit of ammo testing and maybe you can benifit from my experience.

with my pistol on a bag rest, I tested quite a number of ammos, all subsonic, from most of the major manufacturers. surprisingly, I found that CCI SV, which is the most popular ammo in my pistol league, grouped at about 1/2 inch at 25 yards. There were quite a number of ammos that grouped better at 3/8th of a inch at 25 yards such that I determined that 3/8th of an inch was the best that I could line up with my red dot and my current eyeball and prescription glasses. Therefore, I selected the cheapest 3/8th inch ammo which surprisingly turned out to be eley sport. I also found out that there is a moderate difference in recoil between the ammos, sk pistol match special recoils the most of the ammos tested, whereas eley sport was one of the least recoiling that I could determine.

currently, I am shooting through my second case of eley sport and am very satified with the results.

What I recommend is that you try a couple different ammos, determine the accuracy of your eyeball, glasses, and equipment, and then use the information to select the ammo for your gun.

Regards,
Cranky

The discussions on FP accuracy and ammunition are fascinating for me, in part because these guns for me always were just an alternative to rifles at 25-200 yards for precision shooting.

From my experience (or is it my misunderstanding and inexperience?) of using this type of gun since the 1950's but never in sports competition, the main determinants of accuracy are :

accuracy of aim, and timing of firing from the moment when the aim is fixed,

consistency of the MV, and barrel vibration pattern from the cartridge,

degree AND consistency of rotation of the gun at the wrist when fired, BEFORE the bullet leaves the muzzle,

muzzle blast effects on bullet path and stability,

effects of supersonic-subsonic transition,

wind drift,

and

Annie Oakley effects.

A lot of these are not related to the specific ammunition used, but to the gun itself or to shooting technique. The barrel vibration pattern is related to the specific ammunition, because it changes with the rate of pressure development in the cartridge and barrel, and burn rate and flame temperature of the powder. That however is a "second order" effect. The main factors affected by the cartridge are the MV, consistency, blast effect as the bullet leaves the gun, sonic transition, and bullet momentum/inertia related drift.

Variation in the pressure generated is roughly proportional to [1/(free space in powder)] to the 3rd power. As a result, the degree of powder packing is very important for both primer burn rate and powder burn rate. Depth of bullet seating therefore is very important because this determines the packing density, as is consistency of powder charge. Rim thickness is tertiary, primarily affecting ignition rate and temperature of the primer.

Secondarily, but only secondarily, all of this affects the vibration pattern and amplitude of the barrel.

Primer ignition is a piezoelectric effect, and therefore the initial timing of ignition is not closely related to rim thickness. However, the burn rate once ignited does depend on the free space available to the primer, and rim thickness.

When the bullet leaves the barrel, muzzle blast effects at the base of the bullet distort its path. This can reduced by a muzzle break, counterboring the barrel, or a boat tail bullet. The main approach is to use a low velocity ammunition, with minimum muzzle blast. The old Eley Zimmer was the ultimate in this, and could be extremely accurate in free pistols. RWS FP50 was second in line, with slightly higher MV but much better consistency in seating depth. Both are gone, but Fiocchi occasionally makes an Exacta in a slightly higher MV range.

The disturbance of bullet path at the supersonic transition is marked, but this is very abrupt. It is not gradual, unless the bullet is ascending or descending in altitude at the same time, or air temperature is changing drastically by going across a marked thermocline. This is a second reason that supersonic ammunition is not usually used for FP use, UNLESS the target is within the supersonic speed range. If the subsonic transition does not occur while the bullet is in flight, it has no effect.

Otherwise, wind drift is just what: a vector related drift. The sonic transition can behave like wind drift in a sense, but it really doesn't act like wind drift. It's a random inaccuracy effect, while wind drift is very consistent unless the wind is changing directly while the bullet is on its path.

The Aguila 60gm subsonic bullets do give very good accuracy with standard FP rifling, IF the cartridges are sorted for consistency. Otherwise, they are poor. A higher twist rate does not work well, because it drops the MV too much, and introduced too much wobble in their not-the-most-precise bullets.

I have not tried extremely high MV (over 1700 fps) in a free pistol. In other handguns with 5-6" barrels, the highest I've used is about 3600 fps. Accuracy seemed to deteriorate due to problems in bullet stability. This also was the Swedish experience with testing HV rifle cartridges in the 4000-5500 FPS range, including when the target was within the supersonic flight path range.

Some FP shooters have found rifle HV ammunition to be much better than standard in FP shooting. For this to work the velocity must be high enough that the sonic transition does not occur before the target, the cartridges must be extremely consistent in burn rate and pressure, and ideally, either the barrel is counterbored or a muzzle break is used. Most likely the increased accuracy they reported is from a change in barrel vibration pattern, and not shorter flight time in the barrel (which was why the user tried this in competition).

For Joel's use, the muzzle break on one of his FP will alter the effects of HV ammunition blast, but will not change the super-subsonic transition effect. Pistol barrels (2-6") do not give much higher velocity with HV ammunition than with standard due to the incomplete powder burn. The large blast however does worsen accuracy, as does the super-subsonic transition that occurs very soon after leaving the barrel. With a 10" barrel (or 8, 11, or 12 for some FP), the MV is closer to that from a rifle with many cartridges (but usually not equal to it). However, the same issues apply.

Recoil is important in the FP, because it is not in a straight line, except for one FP (the Steyr). All others rotate at the wrist BEFORE the bullet leaves the barrel. This is the reason that the best FP designs place the barrel as low as possible (and with the Steyr, at the exact center of the wrist), and reduce the moment (lever arm) of the gun on the wrist pivot. That way, the rotation BEFORE the bullet exits the gun is minimized, and easiest for compensation by the shooter.

Another issue with FP ammunition is chamber size. Some FP use a very tight chamber dimension. Some "standard" ammunition becomes quite difficult to load, or to eject due to that. This does not affect accuracy, but it does affect convenience, or if dealing with 100 targets in 100 seconds, speed of operation.

Finally, there is the Annie Oakley effect. Her accuracy, consistently, was far beyond what should have been obtainable under the laws of physics and rules of statistics, with the cartridges and guns of that day. I remain baffled by how she did it, but after trying poor quality ammunition (very old Soviet Temp ammunition) in a variety of guns, one possibility is that she found a way to utilize chaotic behavior of the guns and ammunition in a useful way.

Anyway, that's my village idiot's view of FP ammunition in FP use.

Please keep in mind, this idiot's perspective is from uses of these guns that did not involve their use in competition in a target shooting setting/ It is from use of the guns where the requirements were accuracy better than 0.5 MOA and ideally better than 0.2 MOA under what could be very adverse conditions, at distances from 25 to 200 yards. That's quite different from the usual requirements of FP shooting.

Umm, Annie Oakley used .44 cal shot shells in some of her performances:

http://annieoakleycenterfoundation.org/faq4.html

My apology. I should have been more specific .... edge-on card splitting at 90 feet, followed by hitting the falling pieces with separate shots demonstration of hers was the specific action that exceeded predicted ability for the ammunition and guns of the time.

The video in the link above also is interesting .... the accuracy in that is within what would be expected from guns and ammunition of the day, if the perspective on distance is correct.

Give CCI Quiet a try for practice.

I haven't seen anybody talk about the 20 Grain Aguilla low velocity stuff....
2 different rounds, one at 350 FPS the other at 500FPS.

Wouldn't that be much too slow and light for 50 meters?

spektr wrote:I haven't seen anybody talk about the 20 Grain Aguilla low velocity stuff....
2 different rounds, one at 350 FPS the other at 500FPS.

Tried it - very inaccurate and dirty.