Ever wonder about.....

[philthephlier]

bullet rpm in flight. Take a 45 ACP bullet at 900 fps coming from a barrel with a 1 in 10" twist. 900 feet X 12" per foot is 10,800" divided by rate of twist of 10" is 1080 revolutions per second or 64,800 rpm. A 30-06 at 2700 fps with the same rate of twist is 194.400 rpm. Incredible. Eh?

[Reloader06]

Amazing anything stays together at all.

Matt

[Dframe]

I've done a few of those calculations in the past and have always been amazed. I'm surprised that some soft boolits are not distorted by the huge inertial forces undergone by a bullet in flight. I've also can not imagine how lube could remain on what is nearly the surface of the bullet. But recovered bullets always seem to still have lube in the grooves.

[noylj]

It isn't the rpm, it is how many revolutions does the bullet go through to reach the target. It is NOT in flight for even a minute;
Now, if we fired the bullet in space, where the bullet could be in flight "forever," we might see some bullets being dusted.

[Centaur 1]

Anyone who's ever seen a grinding wheel fly apart can appreciate how fast this is, and they only spin at around 3400 rpm's. Here's youtube video of a bullet spinning on a frozen lake.

http://www.youtube.com/watch?v=0h3MBNpQHS0

[Larry Gibson]

Is someone baiting me............:drinks:

Larry Gibson

[22Short]

I just finished watching a "Mythbusters" episode about the frozen lake and the spinning bullet. Confirmed. It reminded me of an experience I had surrounded by sand dunes, where it worked even better... I fired a 45 ACP at a dune about 50 feet away and the bullet deflected up at a low velocity, landed about six feet to my right and proceeded to spin at an unbelievable speed, buzzing and dancing for what seemed to me to be at least 20 seconds. Anybody here have a similar experience?

[MtGun44]

Not personally,but Hatcher reported that .30 cal bullets fired straight up and landing nearby
hit base first and were still spinning quite rapidly when they came down.

Pretty interesting to see bullets in a .22-250 or .220 Swift detonate in midair if driven too
hard. HUGE centrifugal loads, and as they travel through the air at Mach 3+ they are
getting heated by air friction drag. I figure as they warm up they materials weaken a bit
and if they are right on the structural edge - a blue smoke puff and no hole in the target.

Couldn't figure it for two rounds working up some hot .22-250 loads with thin jacketed
50 gr bullets, one hole in the target, then no hole, and no hole again, finally guessed
and fired one with my head up, not looking through the scope and saw the puff as the
bullet blew. Got some harder jacketed projectiles for that load.

The rifles are way over 200,000 rpms in some cases.

Bill

[OBXPilgrim]

Is someone baiting me............:drinks:

Larry Gibson

I don't think so, most of the folks posting have only been on a couple years or so (except MtGun44). Good times......

I saw the Mythbusters show last night as well. Interesting. I heard a story from a vet once that a guy saw a bullet spinning in the dirt next to him, and tried to pick it up - blistered burns.

[gray wolf]

Not fer nutin but I thought 45 ACP had a 1/16 barrel ??

[skeet1]

I bought what I think were Hornady 50 gr. SX 2nds about 30 years ago. I don't know what was wrong with them but even in my .222 they left a vapor trail through the air like they were shedding some of the lead off the nose. They shot OK and they killed a lot of ground squirrels in Colorado when I lived there. They would not shoot in anything larger than .222 without coming apart. It was kind of fun to watch the vapor trail all the way to the target.

Ken

[cbrick]

Ever wonder about bullet rpm in flight.

Seems to me there was a post or two about that very subject. :coffeecom

Now lets see, who was that? :rolleyes:

Rick

[Wayne Smith]

Is someone baiting me............:drinks:

Larry Gibson

I was wondering that too, Larry. I was gonna tell them to do a search for your posts.

[Larry Gibson]

I bought what I think were Hornady 50 gr. SX 2nds about 30 years ago. I don't know what was wrong with them but even in my .222 they left a vapor trail through the air like they were shedding some of the lead off the nose. They shot OK and they killed a lot of ground squirrels in Colorado when I lived there. They would not shoot in anything larger than .222 without coming apart. It was kind of fun to watch the vapor trail all the way to the target.

Ken

The 222 Rem was the first cartridge I saw the vapor trails with also, was using the 50 gr Sierra Blitz at 3350 fps back in '75. Swithced to the 50 gr SX and the same thing. Tried them in the .223 at 3400 fps and several didn't make it to the target, puff of smoke at 40 - 50 yards. I had a chronograph back then so the velocities are correct. Was puzzling at first until I discovered the concept of RPM via an article in one of the gun magazines. The .222 had a 14" twist and the .223 had a 12" twist. Switched to the 55 gr SX in both which lowered the velocity and RPm and have been a happy varminter with that bullet ever since. It is my preferred bullet in 12 and 14' twist .222s and .223s.

Larry Gibson

[rays308]

Had some 40gr XTPs that would explode out of a 22-250. I was told they were about 20yds out when they vaporized. If they weren't exploding at the muzzle, they must have been swelling until finally they burst.

I wondered what distortions they must have gone through before letting go. Kind of like a drop of water falling through the air or a balloon getting bigger.

Might have a little to do with over speeding boolits to. Swells out of round and goes off course.

[Centaur 1]

A dremel tool on high speed rotates at 35,000 rpm's, so most boolits spin 3-5 times faster. Even if they don't fly apart with those kinds of rotational forces, it's amazing that slight imperfections don't cause them to fly off at wierd angles.