[samuel]

Quote:       Originally Posted by nathangdad

You cannot build a theoretically perfect bullet exactly balanced around a centerline from tip to base with perfect curvature toward the tip. IF any bullet stays airborne long enough stabilizing spin will slow and the tip will begin to move off center. At that moment air pressure is greater on one side of the bullet and less on the other side. Thus what begins as a slight wobble will become tumbling (keyholing). The reason people believe any bullet will not keyhole is that the bullet slows and gravity brings it to the ground before keyholing can occur. The .45 ACP is a short, heavy bullet leaving the barrel at a relatively slow speed without a great deal of stabilizing spin. Therefore it can keyhole before hitting the ground. The lesson to be learned is the greater the diameter of the bullet to the length of the bullet, the slower the velocity, and a reduced rate of stabilizing spin will hasten the keyholing effect. Beyond the .45 ACP you might wish to consider some of the black powder projectiles as obvious candidates for keyholing (especially the larger bore rifles). However, as I mentioned in a prior post, keyholing is not an entirely undesired effect when maximum stopping power is desired. A heavy projectile keyholing will generate a larger entrance cavity and will generally not shoot through the target thus imparting full energy to the target.

Go to Wikipedia and look all of this up.It states in there,the larger the projectile the easier it is to stabilise.also there is a quote about spin,it has a formula and then:-"As the spin rate decreases more slowly than the velocity the gyroscopic stability factor at least close to the muzzle,continuously increases.an practical example is shown in a figure(cant show it).Thus,if a bullet is gyroscopically stable at the muzzle,it will be gyroscopically stable for the rest of it,s flight." In other words the bigger the diameter the easier it is to stabilise and the slower the forward motion the more the spin stabilises.It is all in Wikipedia and a whole lot more I am going to read to learn and refresh my memory.Try getting the facts sometime instead of an opinion. Merry Christmas. sam.

[ouch]

45 ACP is a good round. Make sure you shoot them at enough velocity. My Hipoint will cycle them at lower velocity than the P90.

At some point the round will be traveling at the direction that it was shot but will be nose up at the target.

For comparison look at a long pass or kick at a football game. They are nose up and are still spinning true. Nathansdad is right

[lefty o]

no he's not.

[sammoh]

I'm going to have to say no on this issue. Nathansdad isn't right. I've got a couple of 1911 knockoffs and after replacing the barrels in both guns with actual Colt barrels, I've been able to hit paper at 100 yards (talk about having to lob the ball...). Even at those distances, there was no keyholing.

Just a note, I was grouping about 8 inches at 100 yds. I was just glad to hit paper. With cheap Wal-mart purchased Winchester 230gr ball, I was shooting 4 and a half inches above the target.

[Mooseman684]

If an insufficient twist rate is used, the bullet will begin to yaw and then tumble; this is usually seen as "keyholing", where bullets leave elongated holes in the target as they strike at an angle. Once the bullet starts to yaw, any hope of accuracy is lost, as the bullet will begin to veer off in random directions as it precesses.

Conversely, too-high rate of twist can also cause problems too. The excessive twist can cause accelerated barrel wear, and in high velocity bullets an excessive twist can cause bullets to literally tear themselves apart under the centripetal force. A higher twist than needed can also cause more subtle problems with accuracy: Any inconsistency in the bullet, such as a void that causes an unequal distribution of mass, may be magnified by the spin. Undersized bullets also have problems, as they may not enter the rifling exactly concentric and coaxial to the bore, and excess twist will exacerbate the accuracy problems this causes. Lastly, excessive spinning causes a reduction in the lateral kinetic energy of a projectile, thereby reducing its destructive power (the energy instead becomes rotational kinetic energy).
You can buy perfect Bullets...They are made on a screw machine and are very expensive, but they are perfect in every aspect of the word. They do not vary in weight or dimension and tolerances are closer than can be measured.To say..."You cannot build a theoretically perfect bullet exactly
balanced around a centerline from tip to base with
perfect curvature toward the tip." is just WRONG !!!
Also ,JR is right... Shooting unbacked paper targets stapled on a wood frame can appear as keyholed due to the paper stretching as the bullet tries to go thru, tearing it and giving the appearance of tumbling.

Rich

[micallen]

I've shot probably 80 rounds of 200 grain SWC's and no keyholing. Also used cardboard targets.

[samuel]

Some people will tell you anything,like it is natural for a .45acp to keyhole.I advise remembering their name and being ready not to take much credence in the next post they write.Meanwhile,I am glad you got it straightened out from other good advice. sam.

[runfiverun]

if you are not pushing that 230 over about 700 or so it could easily k-hole
you never said what type of ammo you were using
or temp if outside.
the hole in your backer will appear to make key holes also

[Wingwiper]

I just read all of these posts with interest.
I do have a question before my comment.

Sam you said "By the way,the place I saw .40,s and.45,s fired 200yds was rhe police academy in,Tenn..They were practicing laying down suppressive fire to aid a fellow officer that was pinned down.At 200yds the bullets were still hitting point first. sam.'

Does that mean as a observer you then walked down to the targets and examined them all and looked at all of the holes? I know at our ranges, observers are not allowed off of the Ready Line. Just curious how you can make such a statement with so much commintment.

I don't know about .45 or any other pistol ammo but as a rifle competitor, I know for certain that if the Round is damaged as it enters the chamber, such as nicked or scratched it may cause keyholing, depending on the range you are firing at. We have had it happened and would ALWAYS examine our ammo before the Relay. If we received any damaged ammo we exchanged it and you can examine the firearm by cycling without firing.

I have also seen keyholing in cold tempetures and in rain, I can't say it was EVERY round fired though. I have been a Pit Pig as the other relays would fire and you see a lot while in the Butts.

I also remember once we were practicing in sub zero tempeture before a March Match for FORSCOM and we had a heated trailer that we would get into position in and then stick the muzzles out and fire. It was February in te Great North and the 5.56mm would hardly penetrate the cardboard at 300 yds and many of the rounds were embedded sideways in the cardboard. There were 8 of us practicing that day and figured it was the Extreme cold that affected them. I do not know, I do know they were not thru the cardboard and they were sideways. Someone told us the cold affected the powder burn, I am only a shooter, I wouldn't know if that was true or not.

I also know for a fact that in the early 90s the old 5.56mm was still accepted in matches and you had a choice of Green Tip or the older. When we first starting using the Green Tip, our coach would occassionally watch the WASH of a round go between the Target frames. WE had it happen twice in one 400 yd relay. We asked Matt Mcullum the Armorer from MTU Memphis what that was all about and he stated that the Green Tip had a core that was NOT always center balanced and would get a wobble that would take it off of its intended course. From te day on, we fired the OLD 5.56mm ammo in the A2s and never had another wobble to that proportion. Damage ammo was something we were always on the look out for and we would not allow the ammo to sit in the HOT Sun either as we were firing prone slow fire.

These are my observations from experiences and I will now read the responses on what the EXPERTS feel were the cause or if we were told correctly.

[nathangdad]

I seem to get a number of strange responses when I post concerning keyholing of bullets or shotgun slugs from rifled barrels eventually destabilizing if they are in the air for a long enough period of time.

Most people fight against this concept but in reality objects propelled
through the air (bullets, slugs) are not perfectely balanced front to rear
and/or around the centerline. If they stay in the air long enough they will destabilize in flight. They cannot gain rotational momentum after they leave the barrel.

So, I am not going to reply to any more statements of disbelief.
If you want to believe you have a cartridge that just flies true
forever into the wild blue, I leave you with your belief.

[Taurus Fan]

OK ,stop the presses: If your bullets are keyholing, they'd be erratic and scattered all over the place. What kind of accuracy are you getting? That'll answer your question. Even if you have huge shot groups, I seriously doubt they're keyholing, unless you have a barrel with no rifling at all.