Velocity and accuracy

L

L. Boscoe

New member
as a purely recreational shooter of 45acp, I tend toward kinder gentler loads.
I occurs to me as a retired technical person, that there is probably a relationship between velocity and accuracy.
Right now, I have coated and plated 200gr swc rounds and some 185 swc coated I haven't tried yet.
Norma has 45acp in 200 gr hollow point that they say is specially designed for
accuracy. I ordered some of those, but they are $$. Norma says theirs are in the 820fps range.
So the question: at what fps does accuracy suffer, given 25yard or less distance?
I will be chronographing several loads next week, but won't have any opinion
on accuracy until much later.:cool:
 
I shot NRA Bullseye Match , 22 LR , 38 Special & 45 acp , for a number of years .
3 gun Match shooting with target ammo involves a lot of shooting ... 10 shots Slow Fire , 10 shots Timed Fire and 10 shots Rapid Fire ... 30 shots in each caliber .
You want a accurate load but one with a light bullet with just enough velocity to reach the target . The recoil must be low so all the shooting doesn't pound you during a match .

Now some of the most accurate loads I have ever fired out of a 45 acp were handloads on the hot side with Speer 225 gr. JHP's ... they were probably over todays book Max. but they would group into 1 ragged hole at 25 yards ... we were trying for 1000 fps for hog hunting loads in our 1911's and the book claimed that load was 1000 fps !
My 45 acp target load was a cast 200 gr.SWC with 5.0 grs. Unique at 725 fps .

So both loads are accurate ... one at 725 fps and the other at 1000 fps !
I don't think you can say at X-number of fps accuracy suffers . Each bullets design , your guns rifling twist and I'm sure a few other factors have a lot to do with what velocity a particular bullet hits it's accuracy sweet spot .

I have learned that in 45 acp the starting load or just a little above starting, is usually a good place to start . The pistol has to function , so loads must be heavier than a revolver would allow .
In 45 acp with 200 gr. cast or coated lead SWC the starting loads are between 700 fps and 800 fps .
My all around general use , tin can , range load in 45 acp is the 200 gr, lead SWC over 5.2 grains Unique for about 750 fps ...accurate out of my 1911 and it doesn't beat the gun or shooter .
Gary
 
Coming from a pistol standpoint, if velocity effected accuracy, they why are rifles a thing?

The only factor that I can think of is bullets going transsonic. With rifles accuracy can degrade rapidly when going through the transonic range going sub sonic.

With handguns it could be reasonably easy to get them into the transonic range or unstable out of the gun. or get them supersonic only to have them drop through the transonic range 15-20yds later and become unstable at the target.

Personally I would say the shooters ability, the quality of the firearm, and the consistency of the ammunition will have more of an effect on accuracy than velocity, presuming you stay a reasonable distance away from the speed of sound.
 
The velocity (speed) of the bullet is not the prime factor in accuracy. Not even in the top few. It has to be enough to push the bullet out of the barrel, and not so high that the bullet strips the rifling's grip, other than that, the actual FPS does not play a part in accuracy.

Where velocity does play a big part in accuracy is consistency. The actual speed doesn't matter, what matters is that each round is moving at the SAME speed.

Not visible to the naked eye but every gun barrel "whips" as the bullet travels down it. This moves the muzzle and this means that bullets moving at different speeds exit the muzzle at slightly different times, This means they exit the barrel at different points on the muzzle's arc of movement.

Accuracy as commonly defined is "putting all the shots in one hole" or as close as we can achieve (small groups). TO do that, each shot needs to exit the barrel at the same point of its movement arc as the one before it, and the one after.

This is why shot to shot velocity differences matter, and why we look at "extreme spread" in the velocity of a load as a measure of its potential accuracy.

Bullets are "designed" for accuracy by ensuring their uniformity, and suitability of materials for the expected range velocities, and for their fit in the barrel.

I would expect better accuracy from a group of shots where they are all in the "820's" fps than from a group where some are in the 820s and some are in the 700s and some are in the 900s for speed.

it is load consistency that makes accuracy, not the precise speed in fps.

I will also add that guns are individuals and a certain gun may prefer (be more accurate) with a certain bullet at a certain speed, more than it is with that same bullet at a different speed.

But this is not due to the speed alone, but due to factors unique to THAT gun and ammo combination. And whether its most accurate at 800fps or 1000fps with bullet A is a result of the gun, the bullet and the load "working well together" not just the amount of velocity in fps.
 
I would add that stability is a factor. Usually the velocity that gets that is pretty wide.

Factors are the barrel twist, the bullet type, the BC and the velocity shot at.

As I recall, there is a formula (can find it on internet) and 1.5 and over is stable.
 
There are a lot of versions of the simplified estimator Don Miller came up with, but it is geared mainly toward rifle bullets. One that estimates axial and transverse moments of inertial to solve the basic stability equation is here, but it takes more input. It does, however, show twists and stability through the transonic range. For a 230-grain .451 round nose military (the longest at 0.68" and most difficult to stabilize) the regular 16" twist is so much faster than necessary (about 40") it is impossible to have a twist-rate-related stability failure. This so-called overstabilization hurts nothing because the actual R.P.M. of the bullet is nowhere near fast enough to cause failure coming out of the pistol, and benchrest accuracy isn't required. It would be interesting to try one with a slower twist, but I've seen experiments done to show handgun ammunition likes a bit more spin than is considered optimal in supersonic rifle bullets.

As far as velocity effects on accuracy, keep in mind that well-made air guns can put ten pellets through the same hole at 10 meters going just around 400 fps. It is consistency and not velocity that matters to this. In firearms, especially those with large capacity cases, lowering velocity means lowering the case fill, making consistent ignition more difficult to guarantee. This results in irregular velocities. Also, at lower velocities and longer ranges, the drop of the bullet becomes significant. The bullet's fall is becoming more and more rapidly due to acceleration by gravity, so the difference in time of flight caused by variation in velocity makes more difference to the vertical point of impact than at shorter ranges, and thus, irregular ignition can cause accuracy problems that way. In general, a fuller case and higher peak pressures make a powder burn more consistently if all else is equal. Usually, all else isn't equal and the change in vertical POI from a ballistics program assumes a perfectly rigid gun rather than one with muzzle rise and whip, which can, if times correctly, tend to compensate some for velocity changes. Nonetheless, it has long been reported by many benchrest competitors that they usually find their most accurate load at close to maximum, and ignition consistency is a likely candidate to explain this observation.
 
Good stuff, Nick- I will test the Norma against hand loads and some factory loads that, while I don't know the speed now, shoot pretty hot with mucho recoil.
Unfortunately, no Ransom rest is available, so they will be shot hand rest as
best as I can.
 
no Ransom rest is available, so they will be shot hand rest as
best as I can.
Click to expand...

yeah, and if you manage to put 5 .45caliber bullets in one ragged hole, probably best to keep it to yourself, otherwise, some one will post how "that's not accurate..." :rolleyes:

though I think it is..
 
44 AMP said:
yeah, and if you manage to put 5 .45caliber bullets in one ragged hole, probably best to keep it to yourself, otherwise, some one will post how "that's not accurate..." :rolleyes:

though I think it is..
Click to expand...

Some people think the arrangement of hits is more important than the group size? :rolleyes:

I guess we can throw out our rulers. :rolleyes:
 
I've shot some competition pistol, including a nice 1911 in .45 ACP. Better shooters than I told me 185 or 200 grain lead sem-wadcutters and just enough Bullseye powder to have the gun function reliably was the ticket to success.

I used Hornady swaged lead 200 grain for a while and then switched to 185 grain because they were a little cheaper.

I know you want, heck every shooter wants, as much accuracy in your gun and ammunition as possible, (it can only help your scores right?) but I never felt the need to go with expensive bullets...good enough was more than good enough when there were all the other factors affecting my scores.

P.S. As usual there is a wealth of information in this thread from folks that have "profound knowledge" ("profound knowledge" is a W. Edward Deming thing. It means these folk really know what's actually going on) so take my advice for what it's worth, anecdotal information from one guy.
 
Low recoil is a big concern for Bullseye shooters. You might find a really accurate load at 1,100 fps, but the recoil would be awful.
 
That's correct. The standard 25-yard timed and rapid-fire target black only encompasses the 9-ring. The 10-ring is 3.36 inches at that range and because a scratch score gets you the next higher score, you add your bullet diameter to the ring diameter to figure out how wide your group can be and still clean the target. It works out to 3.811" which is 14.56 moa at 25 yards, so you don't need one-holer precision to clean one. But you are required to fire standing off-hand in Bull's-eye Pistol, and when shooting one-handed, the m1911 tends to jump a bit. So the deal for light 1911 target loads is to minimize sight picture recovery time between shots in timed and rapid-fire, and not to guarantee the highest precision load. At 50 yards, the same ring diameters are used, cutting the angle subtended by the 10-ring+bullet diameter to 7.28 moa and the X-ring+bullet diameter to 4.1 moa, which is about the limit of most accurized copies of the pistol with the best-sorted cast bullets. It takes both accurate ammunition and good shooting technique to clean the 10-ring at 50 yards. Many of the folks I shot bull's-eye matches with years ago had different loads for 50 yards than for 25 yards. Mine prefers 200-grain bullets for precision and needs to have them to clean a 50-yard target in my hands. But it shoots the soft swaged 185's just fine for timed and rapid.
 
For me this is how I look at pistol shooting. A pistol only serves one purpose, self defense since I don’t hunt with a pistol and am not a bullseye shooter. So as far as accuracy goes, if I can empty my gun as fast as I can and keep all hits in a 4” circle out to 15 yds I’ve achieved my goal. So I do all my shooting free hand, no rests even when working up a load. My personal experience is that recoil plays the biggest role in this type of accurate shooting. So I strive for as hot a load that I can shoot to this level of accuracy. This counts in all my pistols, both revolvers in DA and semi auto’s.
 
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