Home Forums Hunting & Shooting Ask The Gunwriters Swift A- Frame in Action

Just got my order from Graf and Sons .... 180 and 200 grainers in .308 cal as well as 150 grainers in .277 cal. Just checked and the 180 grain .308 cal are no longer in stock.

I hadn't seen the 180's for quite some time.

Probably why the BBC's have done so well I'd think. When they're expanded their is very little shank remaining, but their penetration is usually complete and on the far side in the skin.

I shot a nilgai cow center of the chest facing me with my 7x57 using a 160 A-frame and drove it full length into the gut region. Evidently the Crested Caracara doesn’t like lead since when I returned to the gut pile an hour or so later, the bullet was just lying there on the ground - the only thing that remained.

That has not been my experience--and the late Art Alphin explained why in his big handloading book.

Centripital force has little to do with it. Instead, in a bullet with a smaller "mushroom" and a longer shank, the rear of the shank tends to keep the bullet mushroom-forward due to sliding alongside the narrower wound channel. Have seen this a bunch of times with monolithic bullets, especially in heavier (hence longer) weights, where recovered bullets are often found with the expanded end forward.

Have seen plenty of short-shanked bullets, especially bonded, that were actually "backwards" under the hide--because they ended up closer to round in shape--or start out that way, such as a 240-grain hard-cast .44 Magnum. One was a 340-grain .416 Woodleigh that killed a 100-pound fallow deer, which was angling away at around 100 yards. The bullet entered the right rear of the ribcage, and was found barely poking through the hide in the right shoulder--because it had turned around. The sharp rear edge of one of the "petals" had cut through the hide--even though the bullet retained around 90% of its weight

Have seen the same sort of thing many times with short-shanked bullets, when the animal was skinned carefully enough to find the bullet in its final position.

John,
Your experience and mine differ on that point…the length of shank. A solid is nothing but shank and they are known to fail to maintain a straight line. Of course one must consider twist and nose shape too.

Garrett 44 magnum hard cast bullets were well known for both straight and deep penetration.

Bill Stiegers who made the BBC bullets shot hundreds of his bullets into various test media and he firmly believed that the shank length wasn’t important but the shape of the nose of the bullet was much more important. Bill also discovered the more twist would keep the nose forward. If you find a bullet reversed at the end of penetration it is most likely because of not enough twist. Bill ran tests comparing 270 130’s out of 1-10 and his 1-7.5 which illustrated the problem. He used 1-9 and 1-8 twists in the 375AI which produced the same results. If you find petals of a bullet facing forward then it tumbled because of loss of rotational velocity.

Any tests of bullets using reduced velocity ammo are invalid because of the change in rpm resulting from down loading.

Most 416 and 375 barrels are way too slow twist wise.

Shoot a wide expanding bullets out of a fast twist and it will keep the nose forward and maintain a straight path. More velocity increases rotational velocity. So fast twist, high velocity, bonded bullets that get wide are all required. All those factors are musts otherwise you will get the results you observed.

RD

Rick,

That's not what various bullet manufacturers I know have observed when testing bullets in various kinds of media, even in faster twists--and not what I have seen either, including during their tests and mine, which included big cull hunts where dozens of shooters participated on various sizes of game.

Yes, quite often bullets will end up mushroom-forward--as a decades-long employee of a major bullet company put it "they'll all tumble." (He was not just a laboratory tester, but a long-time hunter who did it not as a side-light to his "regular career," but as his career.)

I have seen far too many high-velocity expanding bullets end up backwards or sideways, whether in test media or animals. Have also tested a BUNCH of bullets in several kinds of media, from "soft" to "hard." Some bullets would exit the side of a 2-3 foot chunk of media--and no, none of them were shot with "reduced loads." This includes both solids and softs--though flat-nosed solids (or better yet "cup-pointed") tend to penetrate straighter.

Part of the problem is that animals aren't uniform "test media." If the front end hits a harder part of an animal, a bullet can deflect--and even start tumbling. This is more likely to happen if the bullet expands wider. This of course also extends to stuff the bullet may hit before it even enters the animal. Have told this story before, but once shot at an eland that had a very light thorn-branch close in front of the vital spot "behind" the shoulder. I figured the bullet couldn't hit any of the very few sparse, thin branches if I shot a whole box of ammo--and the bullet was a 250-grain spitzer from a .338 Winchester Magnum started at the typical 2700 fps or so, the range about 200 yards.

The eland ran into the nearby brush, and when we followed it up, found it standing with its head slightly lowered. I shot it again, and the bull dropped. Well, the first bullet HAD hit one of the tiny branches, which was so close to the eland that the pattern of the thorns was plainly visible in the hair around the bullet hole. This was a perfect silhouette of the bullet, which had turned 90 degrees in at most six inches. I sincerely doubt an expanded bullet inside an animal wouldn't deflect at least as much if the edge of the "mushroom" hit, say, the edge of a heavy shoulder-bone--no matter the twist-rate of the barrel.

And no, the standard twist-rates of .375 and .416 barrels are not too slow. One of the interesting factors in twist-rate is that its proportional to caliber. As an example, the 340-grain .416 bullet I mentioned has a "stability factor" in the typical .416 twist-rate of 1-16 that's MUCH higher than a 7mm 175 spitzer in the standard 1-9 twist.

I've seen tests with solids that mirror your post exactly, but at some point once cavitation is over they may go off line or tumble unless nose stabilized

Jwp,

Yep, cavitation has an effect as well on all of this as well!

John,

I always enjoy our exchanges.

Consider that bullet stability calculations measure the bullets passage through air. As you have observed in other writings, the denser air at sea level requires more stability than at higher elevations because the air is denser. Similar differences are temperature dependent. Basic college chemistry pv=nrt etc.

Now consider that an animal is a leather bag full of bone and water. The necessary stability factor to stabilize a bullet in an animal is much much higher. Can’t draw any meaningful conclusions about how much twist is needed based upon that which is needed to move a bullet through air. It is necessary to keep the bullet from tumbling or exhibiting yaw.

These issues are multi factorial eg exceedingly complex. Reminds me of attempting to deal with matrices in college calculus.

RD

Mushroomed bullets travel “point forward” due to shoulder stabiliaztion. This is pretty well understood in terminal ballistics. Same reason a keith style bullet penetrates so straight. As the bullet travels forward, the forces on the outside edge of the bullet front keep the the bullet from turning over.

An expanded bullet or flat nosed solid may turn over near the end of penetration as the forces acting on front decrease as slow down and the force to turn over is greater. Also uneven expansion may turn over as well or as uneven densities

Bullet spin does not keep bullets “stable” in flesh. Think about it. Flesh is 1000 times more dense than air and no amount of twist will keep a bullet stable. Heck you can go unstable by couple thousand feet elevations change in air density. What twist does is potentially give you more stability before entering flesh (angle of incidence). Amounts to few inches difference in straight penetration. This is particularly important for some bullets at short ranges (small deep hollow points for ex) to reach terminal shape (ie blunt front) but after 70-80 yards bullets are pretty stable assuming started that way

I have my doublts on the long shank doing anything for straight penetration. First reason is that the front of an expanded bullet (at least any decent velocity) forces material significantly away from the bullet. In fact, the sides dont touch at all for most of penetration. This is why bullets still spin during penetration until near the end where bullet slows down enough there is no cavity behind front and then rotation stops almost immediately since there is little energy (couple 10s of ft-lbs) there to move anything. It is same reason a bullets rotational velocity in air slows down much less than forward velocity

Lou

John, your experience with an eland and light brush was almost exactly the same as mine just last May in Zimbabwe. I was using 375H&H and 300 grain Swift A-frame. Bullet hit exactly where I aimed, but sideways! Thank goodness the follow up shots had enough penetration from the rear. I could have lost that eland, through no fault of the good Aframe bullet. I like A-Frames.

I posted a photo over in the image gallery section, but don't know how to make it show up here.
https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/galleries/18062284/eland

Interesting! Thanks for posting the photo.

This is not my experience with close to 1000 expanded bullets observed in taking big game from "deer-sized" to 1500+ pounds. Those that were recovered that penetrated in a very straight line were, by a large majority, those that retained a long shank, whether lead-cored or "monolithic."

Could provide plenty of examples, but whatever....

I think that the wider the mushroom the faster the bullet looses angular speed and the more prone it is to tumble.

See those artistic ice skaters spinning wildly with their arms stretched up and hands together?

When they want to stop they spread their arms out.

Maybe someone more illustrated than me in physics can abound on the subject.

You might want to research Col. Alphin's background in ballistics, and actually read his conclusions about longer-shanked expanding bullets.

Thanks MD. I have the Asquare manual. Also have several books on terminal ballisics. I will reread the Asquare chapter. as been a while. I have no doubts on observations. The bullet would have to be oscillating at some pretty extereme angles if shank is keeping it straight. Never seen that in gel unless a bullet spins off in some non-straight direction. Of course gel is not game. In any case I googled shoulder stabilization as described in textbooks for straight penetration and found a video describing what I was referring to:



Lou

I suppose my druthers are for two holes, but naturally appreciate the issue when hunting herd animals. I used Swifts almost exclusively in Africa. Below are 300gr/375 H&H pills recovered (operative word) and one 180gr Hornady Spire Point out of a 300 Weatherby.

L-R
Zebra @125 yds, shoulder shot, perfect broadside on the shoulder
Eland bull175 yds Same
Wildebeest @ 65 yds frontal chest shot.
Impala (300WBY)@ 80 yds This impala was shot quartering towards me on the point of the shoulder and recovered in the opposite ham. This bullet just about lost all of it's core, If memory serves, it weighed about 80gr. All the Swifts were in the 90 plus per cent weight retention.