Failed bullet expansion at close ranges

Pine Marten

Well-Known Member
Hello everyone.

I've been doing some research into different bullets as I'm preparing to start reloading for my 7mm-08, and one of the people I've been speaking to has been using some bullets that I was considering in his .270Win and his 7mm Rem Mag. He's in France and hunts mostly driven roe, which are shot at what we'd consider short ranges (10-50m) whilst on the move. Several roe that he's shot have run up to 100m before keeling over, some seemed not to notice the bullet impact. It seems to me that what he's describing may be the effects of a failure to expand properly. That said, they were all good and dead afterwards. These bullets are bonded soft points, 150gr in the .270, possibly 170 in the 7mmRM. Both of these calibres have considerably higher velocities than a 7mm-08, in the region of 100-200m/s faster. Would I be correct in thinking that the very high velocities so close to the muzzle could be behind the possible expansion failure, and that you'd be less likely to experience something like that at longer range, and with a slower projectile?

Having sort of worked out loads and so on, I'm looking into terminal ballistics now. Don't jump down my throat please, I'm just asking!
 
Hello everyone.

I've been doing some research into different bullets as I'm preparing to start reloading for my 7mm-08, and one of the people I've been speaking to has been using some bullets that I was considering in his .270Win and his 7mm Rem Mag. He's in France and hunts mostly driven roe, which are shot at what we'd consider short ranges (10-50m) whilst on the move. Several roe that he's shot have run up to 100m before keeling over, some seemed not to notice the bullet impact. It seems to me that what he's describing may be the effects of a failure to expand properly. That said, they were all good and dead afterwards. These bullets are bonded soft points, 150gr in the .270, possibly 170 in the 7mmRM. Both of these calibres have considerably higher velocities than a 7mm-08, in the region of 100-200m/s faster. Would I be correct in thinking that the very high velocities so close to the muzzle could be behind the possible expansion failure, and that you'd be less likely to experience something like that at longer range, and with a slower projectile?

Having sort of worked out loads and so on, I'm looking into terminal ballistics now. Don't jump down my throat please, I'm just asking!

10-50m range and "on the move" I tend to take it that you are describing the Battue... Never underestimate the power of adrenaline, a superb painkiller and chemically a fascinating motive force within a (hitherto) healthy animal.

You'll seldom see our UK deer treated to a hefty dose of such a wonderful drug before being shot. We just don't usually do it that way... :rolleyes:
 
expanding bullets expand more the higher the impact velocity , I think the facts are as tamus describes personally.
 
expanding bullets expand more the higher the impact velocity , I think the facts are as tamus describes personally.

Ah, so nothing to do with possible failed expansion, and more to do with stressed deer being surprisingly resilient. This leads me on to ask what exactly, in the physical world, "knockdown power" is.
 
Ah, so nothing to do with possible failed expansion, and more to do with stressed deer being surprisingly resilient. This leads me on to ask what exactly, in the physical world, "knockdown power" is.

a made up phrase to try and explain 'killing' power but due to so many variables it really isn't that useful ?
 
it's a mix of two things, using a far too powerful rifle for this type of hunting (7mm rem mag for one) on such thin skinned game,and in turn, finding that bullets of traditional somewhat stout construction fail to expand at such close ranges,,and velocities probably north of 3000fps.

..and. of course, like tamus said, adrenaline.


at close range driven game, you cannot accurately plan to put the bullet through bone to help initiate expansion, so as an ethical hunter, you have to pick a calibre and chambering, and load it to deliver a bullet which at this range, and on small thin skinned game, will expand readily if not put through bone.

you will probably find a 120-150g partition in 7mm, loaded at a modest MV, will be an exceptional killer for this type of hunting.
 
Thanks PKL, that's a better explanation of what I thought was likely to be happening. On a related point, they tend to really like calibres that we consider very powerful in France. The most popular by miles is 7x64, but after that it's 9.3x62 (heavy and slow, fine for driven shooting), .300 Win Mag is extremely popular too. 270WSM and 338WM are up there too. I have to say that if I was after a specific driven game gun, I'd go slow and heavy like the 9.3 or the 8x57JRS. Things like the 300WM are really for shooting at much longer ranges. Anyway, it doesn't sound like there's anything wrong with my planned bullet of choice. He's just using it wrong.
 
Last edited:
PM,

I think popularity over there is largely due to the old restrictions on military calibres, and the wish to be able to double up as a boar rifle,,for the obvious reasons.

but yes, a stout bullet, delivered fast, on a thin skinned small deer, will only mean one thing...even a BT or similar explosive bullet would more often than not either A. explode on the shoulder, or B. pin hole (depending on what was hit on entry).

the reason I mention the partition is it has fast expansion, and also delivers an exit wound for tracking in woodland...probably, IMHO, the best bullet ever made.
 
All the above seem right. I notice the continental Europeans just can't seem to find hard enough bullets that in turn are supposed to create almost no meat damage. Reading German forums there are two main subjects ...."what calibre and what bullet creates the least meat damage" and "why do my deer run over 100m after a good hit?"
If one has a big game bullet in say 7mmRM that is supposed to go through two shoulders and exit on a red deer sized animal one can guess what kind of energy is dumped into a narrow Roe deer if not even a rib is hit. In those conditions a varmint bullet out of a 223 would put the animal down quicker. I have seen running sika been hit by a 220 swift and just summersaulted. Same point of impact they ran over 100m shot with a 150gr SP from my 30-30.
Hit any animal on the spine or close to it and they'll drop on the spot.
At the end of the day the bullet must match the animal and where one shoots it.
edi
 
All the above seem right. I notice the continental Europeans just can't seem to find hard enough bullets that in turn are supposed to create almost no meat damage. Reading German forums there are two main subjects ...."what calibre and what bullet creates the least meat damage" and "why do my deer run over 100m after a good hit?"

There's a guy on a French forum I use who mentioned that his hunting association forbids the use of rifles on roe. They have to use large shot instead, and it's specifically to prevent meat damage.
 
+1 more speed means more expansion cannot work any other way.


it's not as simple as that, if you take a 160g soft point with a 300 win mag and drive into a roe yearling, it will be almost through the deer before it starts to expand, so there's not 'shockwave' that travels up to the spine, in addition, the temporary wound channel is narrow and pulls together quickly, bleeding is slower, the deer is in a dead run...

take the same bullet in a 7x57 at 2600fps and you will have a bullet that expands just inside the rib cage, drives shock, and blows up the vitals. it collapses quickly.
 
Things like the 300WM are really for shooting at much longer ranges.

not necessarily
200-210gr 300WM bullets are starting at 27-2800fps MV depending on load
the velocity and low drop advantage is less and you have turned it into a big thumper for terminal energy
its is very good at delivering big bullets faster than a 308/30-06


I find that close range shots with the .270 for instance result in over expansion
I shot a stag with 130gr Interlock at the tail end of the year and it was under the offside rib skin
expanded well past the lock ring and dumped over 45% of its weight

ideally I would have preferred an exit but it did the job


it is possible to lose the expansion of a bullet because of the velocity
20gr hollowpoint HMR is an example I know first hand
too close and the pencil through without expansion
 
Last edited:
it's not as simple as that, if you take a 160g soft point with a 300 win mag and drive into a roe yearling, it will be almost through the deer before it starts to expand,

...

take the same bullet in a 7x57 at 2600fps and you will have a bullet that expands just inside the rib cage, drives shock, and blows up the vitals. it collapses quickly.

This is not in keeping with what the physics would dictate. A higher velocity bullet will penetrate less (not that this matters in a roe deer) but there is more energy to do work to deform the bullet and so expansion will tend to be greater and more rapid. The ultimate end point of this situation is the very high velocity bullet that will "blow up" on impact, lightly constructed bullets will do this at low velocity but even the strongest bullet will have a velocity (probably beyond what a rifle can produce) at which it suffers catastrophic failure on impact.

The force involved is proportional to the mass of the bullet and its acceleration. In this case it is actually slowing down rather than speeding up of course so the acceleration is negative. A bullet that is travelling faster will be subject to more negative acceleration and so if the bullet is the same and the path through the animal is the same then the faster bullet will be subject to more force to cause deformation and the energy to cause this deformation will be available "faster." Also, the more the bullet deforms the greater the acceleration will be and so the more work will be done deforming the bullet - it is a kind of vicious circle.
 
This is not in keeping with what the physics would dictate. A higher velocity bullet will penetrate less (not that this matters in a roe deer) but there is more energy to do work to deform the bullet and so expansion will tend to be greater and more rapid. The ultimate end point of this situation is the very high velocity bullet that will "blow up" on impact, lightly constructed bullets will do this at low velocity but even the strongest bullet will have a velocity (probably beyond what a rifle can produce) at which it suffers catastrophic failure on impact.

The force involved is proportional to the mass of the bullet and its acceleration. In this case it is actually slowing down rather than speeding up of course so the acceleration is negative. A bullet that is travelling faster will be subject to more negative acceleration and so if the bullet is the same and the path through the animal is the same then the faster bullet will be subject to more force to cause deformation and the energy to cause this deformation will be available "faster." Also, the more the bullet deforms the greater the acceleration will be and so the more work will be done deforming the bullet - it is a kind of vicious circle.


what you say makes sense, but,,...again, you fail to consider that a think skinned deer like roe has such soft tissue that with semi and stout bullets there's just not enough 'meat' to initiate expansion until the bullet is almost through the deer.
 
what you say makes sense, but,,...again, you fail to consider that a think skinned deer like roe has such soft tissue that with semi and stout bullets there's just not enough 'meat' to initiate expansion until the bullet is almost through the deer.

I see what you mean but too much velocity causes more not less expansion of the projectile.

the higher the impact velocity the sooner expansion initiates so in your roe example slowing down the projectile would have the opposite effect , what would be needed would be a more fragile bullet construction if you wanted to initiate expansion sooner in your example not less velocity.
 
I think there are several factors at play here.

Assuming that this was not purely the effect of adrenaline, I have seen unspooked deer run for 100 yards with no heart after a shot, the issue of whether the bullet is at fault or not depends more on perspective than a right or wrong answer.

At close range and high velocity, you would expect a bullet to expand as much as it's going to. The danger can sometimes be that the bullet blows up and fails to reach the vitals resulting in a runner. In the cases you describe there were not extensive surface wounds that would indicate that this was the case.

Low velocity and long range reduce the expansion potential of the same bullet.

Therefore if a bullet of normal construction is going to pencil through without causing enough damage to kill the beast quickly, it will either be at long range or as a result of some bullet QC issue.

The bullets I am thinking of seem very well made and of a construction that suits velocity, ie bonded and internally reinforced. It seems unlikely that they blew up due to excess velocity for that reason.

Velocity can sometimes also cause hollowpoint type bullets to fail to expand, though this is rare and these bullets are not hollow points.

This leaves as the chief culprit the idea that the bullet is too well constructed almost, so stoutly made that even on a close impact and at high velocity it does not open up enough to cause the usual damage from a soft point.

This is not necessarily a fault, for big game a smaller hole all the way through is much better than a bullet that barely makes it through ribs and hide but utterly devastates the same. This is why a nosler partition is such a versatile bullet compared to say a Swift A-Frame, the latter is a bonded version of the former. The unbounded partition loses it front half in the heart lung area and the almost calibre sized shank that remains usually holds together to exit. The result is good damage in the cavity and an exit. This make it work better on smaller animals such as deer than the A-frame because the latter being bonded tends to expand to about 1.4 calibres and stay that way no matter what it hits. More damage, deeper in always makes for a more sure kill.

You may also want a heavily constructed bullet if you shoot deer through the shoulders to drop them where they stand, assuming a neck shot is not on the cards. A bonded bullet will in this case damage slightly less meat than a conventional.

The net effect of all of this is that if you are receiving reports that a bullet shot a few hundred feet per second and at close range is not expanding enough for quick kills, shooting it from a slower calibre and at longer range is not likely to improve matters in that regard.

Having said all of that, placement of course counts for more than anything and if you are worried you can always shoot them through the shoulders if in or near heavy cover.

Big holes make for faster kills too, the reason a 9.3 is popular is that it will shoot stem to stern on a red stag with ordinary 286 grain bullets and very reliably given the low velocity.
 
I see what you mean but too much velocity causes more not less expansion of the projectile.

the higher the impact velocity the sooner expansion initiates so in your roe example slowing down the projectile would have the opposite effect , what would be needed would be a more fragile bullet construction if you wanted to initiate expansion sooner in your example not less velocity.

I have to apologise for this, but,,you're wrong! LOL...

what I'm trying to say is, yes, more velocity DOES give more expansion, but the bullet needs to hit something of sufficient counterforce to 'initiate' that expansion, and the very soft tissue on roe means that the bullet almost doesn't 'realise' it's entered flesh until about 6-10" into the body, where it 'then' begins expansion,,,which is too late.

if it had been a thick skinned roe deer, the thick skin would probably be enough to initiate expansion with a stout fast bullet,,but it's all about when the bullet starts to expand, and that is not always the second it 'touches' anything, it needs to reach a certain amount of restriction before the expansion begins..

makes sense?
 
Back
Top