Understanding The Phenomenon Of Jacket-Core Separation

I've seen numerous jacket and core separations that were discovered while cleaning dead whitetail deer and feral hogs, however I would not classify them as failures because the game animal was killed quite effectively. These separations usually occur at close distance and high impact velocity is usually the cause for the separation and also resulted in BANG FLOP.

Now having said that I have witnessed several absolute failures.....

130gr Sierra Game King .270win - Shot a LARGE whitetail doe in the shoulder at 125yds distance; she was found dead in a creek 50yds from where she was shot. I was hunting with a doctor that owned the property and while skinning we discovered that the shoulder blade was broken but ZERO damage to the vital organs. After closer look we realized that cause of death was DROWNING after she fell into the creek.

180gr Balistic Silver Tip .300win - While hunting with my cousin I watched him nail a LARGE whitetail buck in the shoulder broadside at 100yds, I was watching in my binoculars when he shot and I'll never forget the massive cloud of hair that blew off this bucks shoulder blade upon impact and watched as it ran off with its left front left bobbing around but otherwise looking quite healthy - we found no blood but tons of hair all over the ground and the buck was never found.

Same stand, same ammo a couple of hours later and a 350lbs+ pig comes out and same thing - Good hit but no blood and pig not found.

The following evening my cousin was hunting another stand close to me with same rifle and ammo. I hear my cousin shoot and he dropped a MASSIVE 8pnt that was standing in tall grass by shooting it in the head just under the left eye.

You would think that a 180gr Balistic silver tip .300Win @ 70yds with a head shot would blow the skull up like a ripe melon..... but no, there was the perfect entrance wound under the left eye and blood coming out it's ears - NO EXIT WOUND!
Not that unusual. Hit in the head or top of the neck, bullet impact can be absorbed by flexibility of neck. I've had it happen several times. Kills them dead but no exit.
 
Alright, Gents. A discussion for you all.

It goes without saying that those of us who've hunted with cup & core bullets... have all experienced jacket-core separation at least once or twice (if not more) in our hunting lives. Especially older hunters like me who began our adventures at a time when bonded or monolithic bullets were completely unheard of.

My question is: Do you always consider jacket-core separation to be an example of bullet failure ?
In today's world, given the plethora (word for the day) of bullet options, I see it more an example of trigger-puller failure - people choosing the wrong bullet for the given conditions.

Cup & core bullets are still a viable option given the expected conditions. My personal (emphasis on personal) rule-of-thumb is when big game live weight reaches ~300+ lbs, I switch to bonded bullets. I switch not because of the live weight, but what the live weight represents - bone structure and chest size. Just more to possibly go wrong on bullet impact.
 
In today's world, given the plethora (word for the day) of bullet options, I see it more an example of trigger-puller failure - people choosing the wrong bullet for the given conditions.

Cup & core bullets are still a viable option given the expected conditions. My personal (emphasis on personal) rule-of-thumb is when big game live weight reaches ~300+ lbs, I switch to bonded bullets. I switch not because of the live weight, but what the live weight represents - bone structure and chest size. Just more to possibly go wrong on bullet impact.
I generally agree with this thought.

I don’t consider it as “Bullet Failure” since the end result is a dead animal even though the core has shed its jacket.
I don't agree with this thought.

when a bullet sheds its jacket, there are a couple things happening, one the bullet is getting lighter (and depending on how many pieces of it, a lot lighter) two, the pieces are likely to divert from their original direction and lastly, the pieces are unlikely to have the weight or integrity to continue to penetrate and do their original job.

i had a sierra game king 175gr (at 2900 fps) come apart on a sitka blacktail deer (under 150#) and recovered the jacket. the deer did die, but, had it been a larger animal or a tougher angle, then the story might not have ended well.

the bullet is truly the most important part of the hunt. if the shot placement is perfect but the bullet comes apart, then a wounded and lost animal is likely.

the historical references of bullets not going as fast, and usually heavy for caliber are in my opinion accurate and mostly correct. the faster moving calibers require a more heavily built bullet to withstand the stresses placed on them with a fast velocity.

kinda why the 3006 with 220 gr bullets got such a great rep. they could not push em fast, they were heavy, good SD and penetrated well. just not a flat shooting bullet. same with 7x57 or 303 brit.

when a bullet comes apart though, if not a failure on THAT animal, it will fail on a larger animal due to lack of penetration and tissue damage.

bullet selection is one of the most important decisions to make regarding a hunt IMHO
 
It is an interesting question. On other forums with more long range hunters I've seen lots of pictures of ELDX bullets and similar bullets that came apart in Elk but still killed well. A friend shot an ELDX through a mid sized grizzly with good results. Another friend shot a 308 150 gr SST through a moose. I don't think a perfect mushroom is as important as a quick kill. I'm going to try some softer bullets this year and see how things go. I'd be tickled if a softer 308 bullet gave performance similar to my .358 for example.
 
It is an interesting question. On other forums with more long range hunters I've seen lots of pictures of ELDX bullets and similar bullets that came apart in Elk but still killed well. A friend shot an ELDX through a mid sized grizzly with good results. Another friend shot a 308 150 gr SST through a moose. I don't think a perfect mushroom is as important as a quick kill. I'm going to try some softer bullets this year and see how things go. I'd be tickled if a softer 308 bullet gave performance similar to my .358 for example.
I think impact velocity and shot placement needs to be matched up with bullet construction. Impact velocities 2000-2500 most c&c bullets work well. Above that, and/or if impacting on heavy bone there is an increased risk of core jacket separation. This is from what I’ve read, not from first hand experimentation of course.

Again, this is why I prefer premium controlled expansion bullets and NOT ultrafast magnums and light for caliber bullets. Being able to shoot from any reasonable shot angle appeals to me.
 
I generally agree with this thought.


I don't agree with this thought.

when a bullet sheds its jacket, there are a couple things happening, one the bullet is getting lighter (and depending on how many pieces of it, a lot lighter) two, the pieces are likely to divert from their original direction and lastly, the pieces are unlikely to have the weight or integrity to continue to penetrate and do their original job.

i had a sierra game king 175gr (at 2900 fps) come apart on a sitka blacktail deer (under 150#) and recovered the jacket. the deer did die, but, had it been a larger animal or a tougher angle, then the story might not have ended well.

the bullet is truly the most important part of the hunt. if the shot placement is perfect but the bullet comes apart, then a wounded and lost animal is likely.

the historical references of bullets not going as fast, and usually heavy for caliber are in my opinion accurate and mostly correct. the faster moving calibers require a more heavily built bullet to withstand the stresses placed on them with a fast velocity.

kinda why the 3006 with 220 gr bullets got such a great rep. they could not push em fast, they were heavy, good SD and penetrated well. just not a flat shooting bullet. same with 7x57 or 303 brit.

when a bullet comes apart though, if not a failure on THAT animal, it will fail on a larger animal due to lack of penetration and tissue damage.

bullet selection is one of the most important decisions to make regarding a hunt IMHO
If you lost the animal and couldn’t examine the bullet, how do you determine it was bullet failure by the core losing its jacket?
 
During the last unpleasantness called COVID I could not find a bonded bullet for sale anywhere for use with cow elk hunting. But I'd been testing ELD-Xs. So, I broke my personal rule about bullet choice based on live weight (see above), but I knew I was breaking my rules and adjusted accordingly.

I hunt mature, dry cow elk which typically weigh in the 400lb - 500lb range, and I was using what was effectively a cup-and-core bullet. Normally, I prefer to break down animals of that size with bonded bullets, but I also knew that approach was asking for problems using the ELD-X. So, over a span of a week, I passed up multiple shooting opportunities until I got what I was looking for; a cow elk broadside and just ever so slightly angling away from me. I sent the bullet tight in the leg crease for a high lung shot, avoiding as much bone as possible. No drama ensued. And I did the same 3 more times during COVID.

So, based on taking 4 elk that way would I recommend using the ELD-X on elk? Absolutely not! I was just jammed up on bullet selection then and adjusted accordingly. These days I've been using the Norma BondStrike bullet and it performs beautifully, just like it's older sibling the Oryx.
 
I think impact velocity and shot placement needs to be matched up with bullet construction. Impact velocities 2000-2500 most c&c bullets work well. Above that, and/or if impacting on heavy bone there is an increased risk of core jacket separation. This is from what I’ve read, not from first hand experimentation of course.

Again, this is why I prefer premium controlled expansion bullets and NOT ultrafast magnums and light for caliber bullets. Being able to shoot from any reasonable shot angle appeals to me.
I agree I want to shoot from any reasonable angle. But I think core separation does not mean a bullet failed. I saw a 125 gr SST bullet come apart in a black bear but it smashed the shoulder bone first shredded the vitals and anchored the bear. Not a failure in my book. It penetrated enough for any angle I would shoot a bear from. For the record I've seen small black bears stop heavy premium bullets if shot through the rear on going away shots. So Texas heart shots should be ruled out for non wounded game with pretty much anything.
Bottom line - I'm rethinking my ideas about bullets. If I don't need premium bullets I don't want to pay the premium price. Actually I think a soft 308 bullet might make a wider hole then a harder .358 bullet. I like that idea as long as it penetrates enough
 
I agree I want to shoot from any reasonable angle. But I think core separation does not mean a bullet failed. I saw a 125 gr SST bullet come apart in a black bear but it smashed the shoulder bone first shredded the vitals and anchored the bear. Not a failure in my book. It penetrated enough for any angle I would shoot a bear from. For the record I've seen small black bears stop heavy premium bullets if shot through the rear on going away shots. So Texas heart shots should be ruled out for non wounded game with pretty much anything.
Bottom line - I'm rethinking my ideas about bullets. If I don't need premium bullets I don't want to pay the premium price. Actually I think a soft 308 bullet might make a wider hole then a harder .358 bullet. I like that idea as long as it penetrates enough
I think heavy for caliber bullets at modest velocities are very unlikely to fail and a great choice for many hunting situations. We should all understand the limitations of our chosen projectile, but I do believe bullets are better than ever.

C&C bullets at high speed on heavy bone/tissue is not optimum, nor are monometal bullets at low velocity for a double lung shot. All projectiles have limitations IMO. Understanding the limitations of your chosen cartridge and projectile is important.
 
Alright, Gents. A discussion for you all.

It goes without saying that those of us who've hunted with cup & core bullets... have all experienced jacket-core separation at least once or twice (if not more) in our hunting lives. Especially older hunters like me who began our adventures at a time when bonded or monolithic bullets were completely unheard of.

My question is: Do you always consider jacket-core separation to be an example of bullet failure ?

Take myself for example:
In 1974, on my life's first Safari to Africa (Kenya)... I lost a huge male lion (over bait) after my bullet (a 300Gr Winchester Silver Tip fired from a .375 Holland & Holland Magnum BRNO ZKK602) had failed to reach the vital organs. After my white hunter, Mr. Cheffings successfully spoored & finished off the lion with his .458 Winchester Magnum B.S.A Majestic... a postmortem revealed that my Winchester Silver Tip had experienced jacket-core separation & failed to penetrate the six inches of hardened feline frontal chest muscle.

In 1989, I attempted to make a double lung shot on a man eating Royal Bengal tiger with a Winchester Super X 175Gr cup & core point fired from my 7x57mm Mauser Churchill Gun Makers Model Deluxe. The animal succumbed to the gunshot wound on the following day. Postmortem revealed that my bullet had broken through the scapula & only penetrated one lung before experiencing jacket-core separation. The man eater died but one can hardly claim this to be a clean dispatch by any stretch of imagination.

Now, on the flip side of things... I've frequently shot (among other game animals) wildebeest & zebra with the aforementioned Winchester Super X soft points for the 7x57mm Mauser. And also (in recent years) the Prvi Partizan 173Gr cup & core soft point. When used on wildebeest & zebra, both the Winchester & the Prvi Partizan 7x57mm Mauser bullets are guaranteed to experience jacket-core separation (especially when hitting hard bone). But the wildebeests and zebras all gave out within mere seconds of getting shot.

So I'm basically asking: Have any of you experienced jacket-core separation with a bullet during the hunt ? And if so, then what was the ammunition & what was the game animal ? And did you successfully drop the animal or not ?

Warmest Regards,
Habib
Yes, several times with old style cup and core bullets. One was a blacktail buck at about 250 yards. He was quartered away and the bullet hit him in the ribs. It was a 150 grain Sierra Gameking. I found the jacket up in the front of the chest cavity.
I also shot another blacktail at about 35 yards with a 7mm RM. The bullet was a 140 grain Nosler Solid Base Boattail. It was a smallish buck and I hit him in the shoulder. There was no exit and not even a bruise on the opposite e defund of the rib cage. No trace of the bullet could be found.
Later I shot another buck at the back edge of the shoulder with the same 7mm and Solid Base Nosler at about 60 yards. He went down kicking then got up running. Thick brush prevented another shot. I was able to track him back into a steep draw. He was on a dusty trail and I could follow his tracks, but there was no blood. I finally spotted him as he stepped behind a big oak. I put another shot into his ribs. That one passed through, and after a short run he fell into the bottom of the gulch. The first bullet had "cratered" on the shoulder with nothing penetrating onto the chest. We didn't find any part of that bullet either.
Even though that bullet was super accurate in my rifle I decided I needed something tougher. Fortunately, that was about the time Nosler came.out with the Accubond bullets. Since I started using them I have killed a lot of animals and have never recovered another bullet.
 
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@Hunter-Habib question was:

My question is: Do you always consider jacket-core separation to be an example of bullet failure ?

If you go back in time when the range of bullets on offer was not comparable to that of today, the answer is NO and that still applies to such bullets that are still in use.

The fact that soft point bullets have lost a significant amount of weight or even completely disintegrated in the game's body was accepted in the past. One have prepared to this and selected the caliber, cartridge and weight of the bullet according to the game and the eventually shooting distance. The fact that there were problems with the magnum calibers that were emerging at the same time was inevitable and contributed to the bad reputation of some of these cartridges, especially from Weatherby.

Nowadays things look but different as many bullet manufacturers more or less promise a weight retention of at least 90% if not almost 100% in the case of lead-free bullets. If such bullets lose the core or parts of it, this can be viewed as a failure, but that does not mean they cannot work well.

Ultimately everything is a question of impact velocity and therefore also the shooting distance. At long range, classic bullets such as the GK from Sierra still work very well, sometimes much better than modern bullets like the Scirocco from Swift, for example.
 
I have experienced core jacket separation on several occasions but have been lucky in never losing an animal. In my experience there are two factors that contribute to this phenomenom. The most common being driving a cup and core bullet too fast beyond its design envelop. The second as mentioned by others is hitting heavy bone. I have altered my reloading for cup and core bullets by using heavy for caliber bullets and when available using round nose bullets. It sounds counterintuitive that a Spitzer bullet would separate more often than a round nose but that has been my experience. As far as partitions losing their front half I don't really consider that bullet failure as that is exactly what they were designed to do and I have never had a partition Fail to kill and do it quickly. Just one old hunters experience.
 
It is an interesting question. On other forums with more long range hunters I've seen lots of pictures of ELDX bullets and similar bullets that came apart in Elk but still killed well. A friend shot an ELDX through a mid sized grizzly with good results. Another friend shot a 308 150 gr SST through a moose. I don't think a perfect mushroom is as important as a quick kill. I'm going to try some softer bullets this year and see how things go. I'd be tickled if a softer 308 bullet gave performance similar to my .358 for example.
Not likely unless using heavy for caliber 308 and light for caliber 358 at medium to longer ranges.
 
I think it has a lot to do with marketing and fashion. Magazines and shows push new ideas and concepts and that's not all bad. We had the magnum craze- flat trajectory so you could reach out. The 300 win mag could do what the 308 does but 100 yards further out. So people reduce the weight of the bullet in their 30-06 to get a flat trajectory. Now the old cup and core 180- 220 gr cup and core was reliable but the same 150 gr cup and core at 3000 fps was not. But the gun writers were doing it. So bonded and mono metals bullets were designed. Now the rise of long range. Shooters at long-range want to spot their shot so recoil is bad. They want heavy for calibre bullets for aerodynamics. So we have newer calibres like 6.5 creedmore. Marketing also tells us that a monometal is better than a 180 gr bonded bullet so we can reduce the weight for better trajectory while in reality the 180 gr simply would not spin stabilise because it has to be longer because of light materials. Marketing tells you it is lighter for better trajectory and because it has 99 percent weight retention… no,it simply cannot be 180 gr and hit the broadside of a barn.

So if you understand bullets and marketing then cup and core are good when used correctly. My 30-06 shoots 180 gr and 220 gr cup and core Interlock and pmp (I think some sort of bonding in the pmp ammo). I would shoot an Eland with either but I would choose shots missing the shoulder bone (which destroys meat anyway). If you have a 300 prc then you are better suited to bonded bullets as the whole point of that caliber is heavy,high BC bullets(so monometal softs are shooting yourself in the foot..) With a 300 win mag, you could use bonded or mono, whatever floats you boat. I think the current long range fashion pushes cup and core hunting bullets beyond their limits and they do fail. But heavy and slow like 308,7x 57 and 30-06 and they are excellent . I have seen many animal taken with these three calibers up to a big eland bull with no bullet failure. by the way I do not consider a loss of weight to be a failure. If a bullet penetrates through the vitals from a reasonable angle reliably then it is succesful. Weight retention does have bearing on penetration and wound channel.

I saw a Remington Core-Lokt which did not fail on a bushbuck but I wasn’t happy with the performance.The ram did not move more than a meter. But it was from a 300 win mag at about 70 m or less. Front of the bullet was gone and the back was pretty much turned inside out like the jacket of the cup and core sometimes. There were bits of jacket with lead adhered to it found in the lungs etc. I think it would have failed on a zebra or Wildebeeste. No exit wounds and it barely made it to the second lung with no bones hit. On a little bushbuck with a 300, I think that is pretty poor. Wasn’t my rifle, but I would guess light bullets at high velocity, I just saw him loading from the Remington box of ammo. He would have been better with a 30-06 and cup and core !
 
IMO - Bullet “failure” is not just core separation but failure of the bullet to perform as expected. If a monolith copper bullet that’s supposed to expand doesn’t, that’s a failure. If you expect an animal to die quickly and in a relatively short period of time (less than an hour) and it doesn’t…regardless of if the animal eventually dies it’s a failure.

The NP can be the perfect bullet for certain game animals because of the energy dump but for the most part lack any consistent straight line penetration. Other non-bonded cup and core designs suffer the same results.

I will continue to use the Barnes TSX/TTSX and Swift A-Frame for all big game animals because of their proven track record.
 
As old hunters from the time when there were no bonded core bullets or monolithic bullets for hunting purpose, we know that in the past, let's say 50 years ago, in nearly all cases one had a jacket-core separation, sometimes even a completely broken bullet in the body of the game.

I also have shot roe-deers and wild boars with the cartridge 8x57IS and SP bullets like the ones on the picture below. There was often not much left of the bullet, but it was enough for shooting light to medium game where not too much depth penetration of the bullet was needed. Nowadays the use of such bullets would be unthinkable.

IMG_0005 (5).jpeg
 
As old hunters from the time when there were no bonded core bullets or monolithic bullets for hunting purpose, we know that in the past, let's say 50 years ago, in nearly all cases one had a jacket-core separation, sometimes even a completely broken bullet in the body of the game.

I also have shot roe-deers and wild boars with the cartridge 8x57IS and SP bullets like the ones on the picture below. There was often not much left of the bullet, but it was enough for shooting light to medium game where not too much depth penetration of the bullet was needed. Nowadays the use of such bullets would be unthinkable.

View attachment 598831
Times have changed, and like it or not things are not going back to the way they were.
 
IMO - Bullet “failure” is not just core separation but failure of the bullet to perform as expected. If a monolith copper bullet that’s supposed to expand doesn’t, that’s a failure. If you expect an animal to die quickly and in a relatively short period of time (less than an hour) and it doesn’t…regardless of if the animal eventually dies it’s a failure.

The NP can be the perfect bullet for certain game animals because of the energy dump but for the most part lack any consistent straight line penetration. Other non-bonded cup and core designs suffer the same results.

I will continue to use the Barnes TSX/TTSX and Swift A-Frame for all big game animals because of their proven track record.
I would change this slightly to ‘failure of the bullet to penetrate and expand as designed given appropriate shot placement.’ Bit darn wordy though, isn’t it.

I bought 208 g LRX for my 300 PRC. I may be pushing the envelope too much with that heavy of a monometal for caliber, but we’ll see.
 
I would change this slightly to ‘failure of the bullet to penetrate and expand as designed given appropriate shot placement.’ Bit darn wordy though, isn’t it.

I bought 208 g LRX for my 300 PRC. I may be pushing the envelope too much with that heavy of a monometal for caliber, but we’ll see.
Should have one hell of a SD!
 
Should have one hell of a SD!
Yes, SD is .313:). MV is 2860 on the box, hope my rifle likes it. Have mostly used the 7 mm RM 160 gr tsx with good results, but am hopeful the ‘long-range features’ increase expansion at normal hunting ranges. It should since Barnes claims expansion down to lower velocity than the TSX or TTSX. We’ll see.

Wonder if it’s a different copper alloy or just the bullet shape and design that’s purported to open better at lower ranges. Of course, could just be marketing nonsense, but I am hopeful it will have great penetration with improved expansion.
 

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