Higher Velocity Can Mean Greater Field Accuracy

[Picher]

It's recognized by many shooters that lower velocity rounds require greater follow-through than higher ones. Shooting .22LR target and benchrest rifles, the rifle tends to move more in recoil prior to the bullet leaving the barrel.

Perhaps it's most evident in handgun and black powder shooting where there is considerable recoil effect, but lower velocity. For instance, with handguns, hotter loads with greater recoil, but higher velocity, tend to shoot lower on paper than lower-velocity target loads.

Therefore, I contend that high-velocity, but lower-recoil rifle cartridges such as .223 Rem, .22-250 Rem and .243 Win, .270 Win, etc.; will tend to shoot closer to point of aim from different positions, both field and benchrest than slower/heavier-recoiling ones because they tend to move the rifle less prior to the bullet leaving the bore than larger, lower velocity cartridges.

Although I've noticed the effect, I don't have extensive testing results to prove it, but you may want to consider velocity verses bullet weight for smaller, through medium-sized game, especially if you shoot at longer ranges from various positions/rests.

 

[MrBorland]

It's recognized by many shooters that lower velocity rounds require greater follow-through than higher ones. Shooting .22LR target and benchrest rifles, the rifle tends to move more in recoil prior to the bullet leaving the barrel...

Therefore, I contend that high-velocity, but lower-recoil rifle cartridges...will tend to shoot closer to point of aim...than slower/heavier-recoiling ones because they tend to move the rifle less prior to the bullet leaving the bore...

I get the feeling you're referring to 2 different phenomena - dwell time vs the amount the muzzle moves while the bullet's still in the barrel.

As far as dwell time, I think it's understood that a slower velocity increases it, and demands good followthrough from the shooter.

As the amount the muzzle moves while the bullet's still in the barrel, though, I've always maintained that physics says it's dependent on the mass of the ejecta, the mass of the gun, and the length of the barrel, but not on velocity. Faster bullets tend to hit lower because they tend to be lighter.

Keep in mind that the higher the bullet velocity, the faster the muzzle moves while the bullet's still in the barrel as well, so time (and therefore velocity) cancels out. It's like 2 guys running - one may run slower for a longer period of time, so he covers the same amount of ground as his speedier counterpart who runs for a shorter period of time.

 

[Picher]

I wasn't considering barrel vibration which is pretty much a constant for a particular load, regardless of hold. Any irregularities in movement of the rifle from ignition to the time the bullet leaves the barrel will cause deviation. Such movements, that include shooter movement or recoil-induced variations, due to hold, rest, etc. will affect POI.

The shorter the barrel time, and recoil-induced motion, the less any inconsistencies in hold and movement will affect a shot.

 

[Erno86]

At short ranges for handguns...a heavier bullet will shoot higher than a lighter bullet, due to the upward vertical recoil impulse.

 

[Double Naught Spy]

Interesting, but I have seen where the same bullet weight, make, and model fired from the same barrel can group differently and different velocities and that higher velocities do not always produce the best results.

Of course, maybe you aren't actually even speaking of accuracy as much as you are bullet drop. Drop and accuracy are not mutually exclusive.

 

[GJSchulze]

I've seen slow motion video of the bullet exiting the barrel of a semi-auto. There is no gun movement of any kind until the bullet leaves the muzzle. This is consistent with physics because it's a closed system until the bullet exits.

 

[Double Naught Spy]

I've seen slow motion video of the bullet exiting the barrel of a semi-auto. There is no gun movement of any kind until the bullet leaves the muzzle. This is consistent with physics because it's a closed system until the bullet exits.

Negative. It is not a closed system. If the barrel isn't moving, it is because it is being held in place or compensated for otherwise.

The amount of movement is often quite small given the amount of time involved and the relative masses between the bullet and the firearm.

Somebody can check my math, but assuming a 36" rifle pivoting at the buttstock during recoil (as opposed to barrel flex), a change of 1/3600" in position of the muzzle before the bullet leaves the barrel will result in the shot being off by an inch at 100 yards. So unless the slow motion footage involves showing a micrometer or a microscope view, then most imagery will be insufficient to show movement that could throw off accuracy.

 

[Jimro]

Picher,

Do you mean "accuracy" as in the shooter can hit where intended?

Or do you mean "precision" as in the rifle/ammo combination is repeatable (making smaller groups than a less precise combo).

Because if you say that higher velocity can increase accuracy "in the field" then you are right to the extent that a higher velocity cartridge will have a longer "point blank zero" than a slower one. However, even the sedate 30-30 Win has a point blank zero over two and a half football fields down range, and going to a barrel burning 7mm Rem Mag or 243 Win can only extend that PBR by another football field. So taking range estimation out of the equation does make a faster round easier to be "accurate" with in that limited scope of performance.

In terms of making smaller groups on paper though, I call utter BS. I've seen accurate black powder rifles (black powder benchrest is a sport I have no interest in, but find fascinating the level of precision achieved is impressive). Also the old black powder cartridge silhouette game achieves very impressive precision. Yes they have much more holdover at the rams than the modern centerfires, but it is the shooter that dictates accuracy.

Jimro

 

[GJSchulze]

Double Naught, I should have said that I was talking about a pistol and that with the bullet just exiting the barrel there was no sign of muzzle flip or of the slide moving.

 

[Double Naught Spy]

Then you are still wrong.

See 1:22 in video here...
http://www.youtube.com/watch?v=HaVhfQcqfGY

 

[Picher]

I was mostly talking about field shots being able to hit where a person, with a sighted-in rifle is trying to hit a relatively small area on game (or whatever) from various field positions and looser or tighter holds than used to sight-in the rifle. Shooter movement, including heartbeat, shake, or whatever, during the dwell (barrel-time) could be a factor, especially when using very low velocity projectiles.

Shooting .22 LR benchrest rifles, most shooters use the "free-recoil" system to minimize extraneous pressures on the rifle that can affect the shot, due to the slight movement of the rifle between ignition and bullet exit. Such bullets are exiting 26-28 inch barrels at around 1,000 fps. A rifle will move about an inch under free-recoil on bags (lubed with baby powder for consistency). Only a small portion of the movement occurs prior to bullet exit, but due to the stock slope on the rear bag, shots will print about 1/4" higher then when held against the shoulder. I believe that proves there is rifle motion prior to bullet exit, especially for lower-velocity rifle bullets.

(Earlier, I used the example of handguns reacting to various loads depending on velocity and recoil and it may have clouded the issue, even though it may apply.)

 

[Bart B.]

Food for thought; i.e. facts for reasoning in these issues.....

All firearms move a bit such that their bore axis points to a different place when the bullet exits compared to where it pointed when the primer fired the round. Some examples:

* Double rifles' barrels toe in at the muzzle. Typically, the bore axis crosses at 10 to 25 yards depending on the recoil. The distance between the muzzle axes is less than the distance between the breech axes. They're "regulated" by moving a wedge between the barrels to zero at 50 or 100 yards. The front sight height on a .500 NE Rigby double I measured was higher above the bore than the rear sight's leaves; proof to me the bore axes rise a bit while the bullets go down the barrel. After all, the recoil axis is above the shooter's shoulder where the stock's butt plate is.

* Handgun front sights' top is higher than their rear sight's tops; go measure them yourself. The bore axis points below the aiming point when the firing pin smacks the primer.

* .22 rimfire free pistols were designed decades ago such that their bore axis aligned with the shooter's arm axis minimizing muzzle axis jump during the time bullets went down the barrel.

* Several people shooting the same rifle with a given load will each have their own zeros on the sights for a given range. This is because each person holds the rifle slightly different and its recoil amout and direction varies a bit while the bullet's going down the barrel. I have observed this with both bolt guns and semiautos with scope and aperture sights "hot gunning" the same rifle and ammo in long range team matches. There's easily a 1 MOA difference. It ain't because they each look through the sights differently; an other decades-old myth.

Regarding high velocity, if a 22 caliber bullet at high velocity is so much better than a 30 caliber one at a medium velocity as far as accuracy is concerned, then why did the US Army get the NRA to allow AR10's in .308 Win. to be classified as a service rifle and finally equip them to shoot scores equal to what 7.62 NATO chambered service rifles, (M1, M1A) did out scoring those using 5.56 NATO rounds? The best 5.56 NATO rifles could not out shoot the best 7.62 NATO ones as far as hitting the target's highest-scoring rings at ranges greater than 600 yards.

It's too darned hard to get low muzzle velocity spreads with higher muzzle velocities in any caliber. Which is why such cartridges are not popular, successful nor desired by folks knowing what's best to score and group well.

 

[Picher]

Bart's comment:

Regarding high velocity, if a 22 caliber bullet at high velocity is so much better than a 30 caliber one at a medium velocity as far as accuracy is concerned, then why did the US Army get the NRA to allow AR10's in .308 Win. to be classified as a service rifle and finally equip them to shoot scores equal to what 7.62 NATO chambered service rifles, (M1, M1A) did out scoring those using 5.56 NATO rounds? The best 5.56 NATO rifles could not out shoot the best 7.62 NATO ones as far as hitting the target's highest-scoring rings at ranges greater than 600 yards.

It's too darned hard to get low muzzle velocity spreads with higher muzzle velocities in any caliber. Which is why such cartridges are not popular, successful nor desired by folks knowing what's best to score and group well.

With the exception of the partial quote above, most of what Bart wrote in his post corroborates my theory. However, I wasn't talking about ultimate target accuracy of various cartridges at 600 yards, but rather, variations in hold and shooter movement as it relates to faster bullets from relatively lower-recoiling rifles compared with heavier-recoiling, slower bullets.

 

[eldermike]

Just as an example: With sufficent magnification you can see gun movement watching through a scope, from a bench rest on a dry fire. Even if it returns to zero as it should on a solid rest the firing pin impact moves the gun.

 

[Bart B.]

Most of the "reticule movement" one sees through a scope when dry firing a rifle is caused by the bouncing of the erector tube off of the two adjustment screw flats. That tube's weight is tiny compared to that of the rifle. And it's got the reticule in it. Sometimes the reticule wires themselves will vibrate a bit themselves.

 

[Picher]

Most reticles today are etched on glass. The older ones, especially on surveyors transits were made of black widow spider web. I had to replace the one on my old transit, after ruining the original.

I've had some cheap scopes that had crappy internals, but some good scope reticles don't seem to move much on dry firing. Some old military guns had very heavy firing pin mechanisms with slow lock time and they would really shake the reticles.

 

[Jimro]

With the exception of the partial quote above, most of what Bart wrote in his post corroborates my theory. However, I wasn't talking about ultimate target accuracy of various cartridges at 600 yards, but rather, variations in hold and shooter movement as it relates to faster bullets from relatively lower-recoiling rifles compared with heavier-recoiling, slower bullets.

If that were the case, then the 7mm Rem Mag should shoot circles around the 308 Win with same mass bullets. For example the 175gr 284 caliber SGK and the 175gr 308 caliber SMK. Shoot the SGK from the big seven, and the SMK from a 308, and the higher velocity of the big seven does what exactly?

We could drop it down to 150gr bullets, and the 7mm Mag would still always have a higher velocity. But would it translate into better field accuracy? Heck we can even compare a 140gr 7mm bullet screaming out at 3200 fps and a sedate 2550 fps 175 smk 308 load and come to the logical conclusion that field accuracy isn't dependent at all on bullet velocity.

So in my experience velocity is not a useful tool in enhancing or predicting accuracy, not at "hunting" ranges with field positions. Even from the bench the accuracy difference between tuned loads is miniscule, and saying that the higher velocity of the 7mm bullet makes up for user error sounds silly. A faster bullet just means you can miss faster.

Jimro

 

[Picher]

Jimro: The 7mm Mag does NOT qualify as a relatively low-recoiling cartridge, given as examples in my posts.

 

[Metal god]

I think I understand what your point is Pitcher and the way I read your post you are correct . When comparing a low velocity round to a high velocity round you will need to hold the rifle more still for a longer period of time . The part that I think some are confused about is what are your velocity's that determine low and high . A 22lr with a velocity of 1200fps will need much more of your concentration then a 223 with a velocity of 3100fps to keep the rifle from moving before the bullet leaves the barrel . I don't think you have the same issue when comparing the 308 @ 2700fps and the 300 WM at 3200fps . I dont think the 308 to 300wm 500fps difference is no where close to the same as the 1900fps difference between the 22lr and the 223 .

 

[Picher]

Metal God: There were several items mentioned; velocity, recoil, and variations in holding the rifle in the field. Sometimes we shoot sitting, standing, or leaning against something like a tree. Provided the cartridge is adequate for the game being shot, the more quickly a bullet leaves the barrel, and the less recoil to move the rifle, the better the shot.

The more comparable the rest, hold and lack of movement of the shooter, compared with the sighting-in conditions; the less velocity and recoil matter for an accurate shot.

(Higher velocity does play a role in hitting running game at fairly long range, because the amount of lead necessary to hit a vital spot, is reduced, but that's not directly related to this discussion.)