.338 Bullet Yaw and Tumble

[Lastgun]

This winter I set out a old chest freezer at 700 yards for a target. Works great, you can easily see your bullet holes.

Thing I found was when hit by both my .308's, the 155gr. SMK bullets passed through both sides clean like a needle.

When hit with .338 Lapua 250gr. Scenars the first side of the freezer was punched through clean but all the .338 bullets keyholed the back side wall of the freezer. All the keyhole bullet exits were oriented the same way horizontal...This load is chrono'd at 2980fps with a 1/10 RH twist and maintains .5 MOA from 100 yards all the way out to 700 yards.

What I am assuming here is even at 700 yards, the .338 Scenars still have a lot of yaw in their flight and when hitting a solid target are tumbling because of this pitched entry...Any one know what's going on for sure?

One thing I would think, anything living gets hit by that massive projectile, then with the bullet tumbling, has to create a much larger diameter but not as deep wound channel then say getting hit by a non yawing bullet.

Sorry no pictures...Dial up and a not so high tech red neck out here.

 

[sunray]

There's a lot of stuff in a freezer wall for a bullet to hit. Don't think I'd claim instability from that.

 

[hoytcanon]

"A lot of yaw in their flight"... but they hit the cooler at 700 yards... you didn't comment on the accuracy... were they in the center of the cooler? Shooting out all four corners?

 

[Lastgun]

There's a lot of stuff in a freezer wall for a bullet to hit. Don't think I'd claim instability from that.

Thing is the .308's go through both sides like a needle every time and the .338's keyhole every time...So I'm thinking yaw...I don't believe the .338's are unstable as the rifle makes a 3 inch group at 700 yards in the calm...When I shot a microwave at the same range I found the same results both with the .308 and the .338.

When a bullet has some yaw in it's flight I guess it does not mean it is not stable in it's flight but when it hits something solid with that yaw it tends to tumble...I think?

I really enjoy shooting different mediums here on the farm in the name of terminal ballistic research as you are at times suprised at the results...Like the other day pounding propane cylinders, 5 gallon pails full of water and farm implement discs...ha ha.

 

[Lastgun]

"A lot of yaw in their flight"... but they hit the cooler at 700 yards... you didn't comment on the accuracy... were they in the center of the cooler? Shooting out all four corners?

The rounds were all hitting around the center mass of the chest freezer...As in not hitting any edges or the compressor and such...The groups are in the range of .5 MOA, under 4 inch groups...When I have a bunch of holes on one side I give the freezer a turn and shoot the new clean side.

The yaw is what I don't understand, how can the bullets fly so true and yet keyhole after impact...I don't think many shoot through two walls on a regular basis as to show the tumbling that occurs after the initial impact with a fairly solid object...If you follow...This could be cutting edge stuff you know?

 

[the wrench]

could be a combination of bullet weight and twist.The military intentionally designed ammo to do this by adjusting bullet weight,velocity etc.

 

[Boomer]

The .338/250 Scenar is a long for caliber bullet whereas the Sierra .308/155 Palma bullet is short for caliber. When a bullet passes through a dry medium, it is less likely to perform as designed, particularly a long bullet who center of gravity is near the base. In a dry medium, a long bullet will have a tendency to bend and hook through the material, whereas in fluid medium, the bullet expands as designed, moving it's center of gravity to the nose, resulting in straight line penetration.

Cast bullets recovered from dry sand - low impact velocity - high target density


.375/380 gr Rhino recovered from an old dry 16"X16" timber - high impact velocity low target density


A trio of .375/380 gr bullets recovered from a snow drift - high impact velocity low target density


A fully expanded .375/380 gr bullet (270 XLC & 300 gr X bullets for comparison) recovered from wet drill mud - high impact velocity high target density


Match bullets though produce unpredictable results at impact: sometimes they grenade, other times they slip through like a needle through cotton, and the target material and/or density doesn't seem to matter . . .

 

[Lastgun]

The .338/250 Scenar is a long for caliber bullet whereas the Sierra .308/155 Palma bullet is short for caliber. When a bullet passes through a dry medium, it is less likely to perform as designed, particularly a long bullet who center of gravity is near the base. In a dry medium, a long bullet will have a tendency to bend and hook through the material, whereas in fluid medium, the bullet expands as designed, moving it's center of gravity to the nose, resulting in straight line penetration.

BINGO...Now that the snow is retreating I have been picking up bullets down range...The .308's are blunted but straight...The .338's are like you say hooked...Where have you been to know this fact, very impressive...I scratched my head when I found these bullets last week but no light came on.

Years ago I used to fly prospectors up and down just inland from the Hudson coast...Saw the bones at Padlei, the black bedrock at Kaminak, the hills at Henik and the seals on the Thlewiaza, Angikuni and Tulamalu...Only got as far north as Baker...Awesome vast country, multitudes of caribou, lake trout every cast in many places, unbelievable black flies except when the wind was howling which was often.

The wife and I were based out of Windy River on Nueltin for ten seasons...Sure do miss that country.