Ammo Accuracy Questions

[brian5271]

[Dark Mod]

1. about a trillion different factors. Subtracting any oddball contingencies and assuming both bullets fit the bore, are the correct size and shape etc..., the largest difference will probably come from velocity.

Velocity dictates where a bullet will impact vertically on target. If there is a large spread from top to bottom, its likely the velocities vary quite a bit. horizontal groupings are usually the shooter.

There are tons of other variables, but without writing a novel, the largest difference a box of factory regular ammo will produce is probably velocity related.

The name of the game is really consistancy, not so much accuracy. Once you find ammo that more or less impacts at the same point every time, you can file down the sites and move that group into the bullseye.

As far as deviation, ive never shot from a ransom rest so i cant be sure. Ill tell you that when i test a ladder of rounds i consider to be imprecise, the spread is over 10" vertically. In fact if im shooting from a rest at 15 yards and some of the shots dont hit paper, i consider it to be prohibitively imprecise and i move on to another load.

math gurus will be able to figure it out. I would assume somewhere around 6" in deviation at 15 yards, and maybe 2 or 3 inches at 7 yards between horrible and great ammo.

2.

I couldnt tell you if 115 or 124 grn projectiles would be more acurate. Ill tell you that 115 grainers are capable of higher velocities, which will equate to a flatter trajectory. This really wont translate over to acuracy, since you dont need high velocity, you need consistent velocity if that makes any sense.

If you need to meet power factor, are shooting at long ranges, or need higher muzzle energy for hunting, would all be factors in choosing a 115 grain bullet vs a 124. Plain old accuracy at close range wont be as important.

[M27]

The name of the game is really consistency, not so much accuracy.

this, accuracy has nothing to do with the first shot, is has to do with the second shot hitting the first.

powder primer and projectile all play into this consistency.

assuming the lawman really is more accurate than the blazer than it is probably fair to say that the lawman is more consistent in manufacturing than the blazer.

find your ammo that is consistent then adjust your sights accordingly

[J-cat]

Gun voodoo.

[nothing4u]

Gun voodoo.

This.

[stevec223]

yep

Gun voodoo.

yep again....keep it low...

[brian5271]

I asked the above questions on a couple of forums and here is what I got out of it; higher quality ammo is not necessarily more accurate, just more predictable primarily due to more consistent materials and manufacturing processes. Either that or it is gun voodoo.

Is that a fair statement?

Last question; can anyone recommend a decent book on this subject that you don’t have to be a genius to follow?

[J-cat]

Lookit:

Here is how this works- you first need an accurate firearm. This means it needs to be mechanically sound with tight clearances so that everything is the same from shot to shot. The bullet to bore fit is critical. The case to chamber fit is critical. Accurate ammo needs to be dimensionally consistent and fit the chamber and bore.

Accurate ammunition is made from consistent components. This means all the bullets, cases, primers, and powder charges are as consistent as possible in the manufacturing process. The powder itself is developed for a particular application, say a 147gr 9mm load, and the ammo is tuned to shoot tight groups from a test barrel.

No one knows why one powder produces better accuracy than another. Manufacturers have the ability to tune the powder composition to suit their application. We can't. All we can do is try a different powder. This is why I said gun voodoo. Even if you have a perfect gun and you assemble perfect ammo, that does not guarantee perfect accuracy. It guarantees a likelihood of perfect accuracy. And that isn't with all loads either. Some custom gun builders have special fixtures allowing them to test barrels before they spend eight hours fitting them to the customer's gun. This is because even the best barrel sometimes just doesn't want to shoot. No one knows why.

[GeoffLinder]

Most "pistols" will put most ammo to the same point of impact round to round (for each ammo type). It usually takes pretty piss poor ammo to not do this. That said, it is typical for different ammo to have a slightly different point of impact in the same gun, but not always. The more consistent the ammo is (OAL, case volume, crimp, powder charge consistency, etc...) the smaller the average group size will be. BUT, some guns favor certain ammo and some do not.

In general, I have found that sight picture consistency coupled with trigger control to be more important for the average shooter than the ammo itself as far as how well anything shoots

[LynnJr]

If you take a look at 22 long rifle ammunition you will quickly learn good ammo shoots very well and poor quality ammo is a waste of time in the same gun.

I don't find this to be exclusive with rimfire ammunition I find it a commonality with all ammunition.

[bubbapug1]

1. First the gun has to be accurate. If your chamber is not concentric to the barrel, than forget it. Also, the barrel must be free to vibrate. Next, do not add anything to the barrel to impede or distort the harmonics of the barrel.

2. The bolt face must be true to the chamber, and the center pin center to the rounds primer

3. The bullets must be consistent around their axis. This is critical to how they spin. Weight is also critical, but not that critical as one may think.

4. The bullet must be loaded into the chamber concentrically. That's why benchrest shooters trim necks and have barrels reamed to fit the neck OD exactly! The best brass to fit a chamber is brass that has been fired in that barrel and than neck sized. Now you have a piece of brass which fits concentrically into the chamber, and a bullet which is seated concentrically into the neck, and fits concentrically into the leads. Besically all the bullet now has to do is be fired and it has a good chance of going straight without any deviation or cant.

5. The powder charge and barrel exit time need to be near a node in the harmonics of the barrel. As the barrel vibrates it creates a sine wave of sorts. When people say they found the sweet spot, what that means is the load velocity allows the bullet to exit the barrel at a point on the sine wave e which varies least based on the load variation....as it at a far point of the curve, which varies the least per unit velocity.

6. Brass internal volume also should be consistent to produce the exact pressure each shot. Variances in volume produce variances in pressure per boyles law P= v x t Pressure = volume x temperature....any scuba diver knows that rule!

7. Primers should be consistent.

8. Crimping pressures have been shown to not affect accuracy except that crimping can and does ruin the concentricity of a bullet, and once that is ruined, the bullet is not stable in rotation or bearing surface, so blow off crimping if possible to excess. All you need to do is hold the bullet in place. You don't need to kill the bullet. If your kinetic bullet puller needs more than 4 whacks to remove the bullet, its probably too tight.

9. You need to aim well......most people don't ...and blame the ammo.

Be honest with yourself and test the ammo on a bench or in prone.

Gun Voodoo...like science, , evolution, etc....its all BS if you watch Faux news....

[GeoffLinder]

Most of that is specific to rifles and rifle ammo (barrel harmonics, concentricity, case volume. etc...), but good stuff nonetheless. OP is mainly talking pistol ammo here.

[brian5271]

I would like to learn more about ballistics in general, can anyone recommend a good book on the subject? One that you do not have to be a rocket scientist to understand.

[bubbapug1]

A GREAT book on accuracy pertaining to firearms and ammunition is called

"Rifle Accuracy" written by Harold Vaughn. It is, without a doubt the best single source on the causes and effects of various modifications done to rifles and ammunition.

The book does delve into math a bit, but there is also a plain English interpretation of the data to explain what the examined issue had pertaining to accuracy.

After you read it you'll realize just how much
"Urban mindless repetitive myths" there are surrounding guns.

[LynnJr]

5. The powder charge and barrel exit time need to be near a node in the harmonics of the barrel. As the barrel vibrates it creates a sine wave of sorts. When people say they found the sweet spot, what that means is the load velocity allows the bullet to exit the barrel at a point on the sine wave e which varies least based on the load variation....as it at a far point of the curve, which varies the least per unit velocity.

Is this what Harold Vaughn wrote in his book?

Another good book on ballistics is called the bullets flight by Dr Mann