EXPANSION AND WEIGHT RETENTION
At what velocity will GS Custom Bullets start expanding?
Our bullets fall into three categories as far as expansion is concerned.
1. GS Custom HP Bullets.
Our original HP Bullets were designed to give a good balance between expansion and weight retention. We always make a caliber recommendation for each bullet and this is based on the expansion criteria for the particular bullet and caliber from 100 metres to the maximum practical range at which that the bullet is likely to be used. Some HP bullets will start expanding from as low as 1500 fps. Others are designed to only start at 2200 or so. Follow our recommendations and, if you are unsure, contact us for further advice. The three bullets on left were recovered from the range backstop and the three on the right, from game.
2. GS Custom FN Solids
The FN Solid Bullet range will expand if driven hard, and is almost impossible to break or bend. If your rifle is capable of the speed required to expand an FN bullet, performance will exceed that of the "paper ballistics". It is strongly advised that you forget about sectional density and all the baggage we have all accumulated regarding the penetration of heavy bullets. Use the lighter FN bullets to get the speed up and take advantage of the FN technology.
From Left to right:
500gr .470 from Elephant, 540gr .510 from elephant, unfired .510, 450gr .458 from stop box at 2450fps, 450gr .458 from stop box at 2000fps, 450gr .458 unfired
Proving the virtually indestructible nature of FN bullets, these bullets were fired into a steel drum filled with sand. From left to right:
270gr from a 378 Weatherby, 270gr from a 375H&H, 270gr .375 unfired, 450gr at 2700fps from a 460 Weatherby, 450gr at 2300fps from a 460 Weatherby, 450gr .458 unfired.
3. GS Custom
Expanding monometallic bullets have been found to be unreliable up to now. In many cases, hollow point monometallic bullets would act like solids on soft game with bad results. To eliminate this problem entirely, HV bullets are designed to expand reliably from as low as 1600 fps. We have driven HV bullets as high as 4700 fps and weight retention remains at a high 80%. This makes GS Custom HV bullets the most versatile premium expanding bullet on the market today.
The mechanism is that an HV bullet will start expanding soon after submerging in tissue. As the HV bullet penetrates, it expands, forming the wound channel for maximum damage. Where the impact speed is below 2500fps, an HV bullet is likely to retain the petals as maximum weight and momentum is required. If impact speed exceeds 2600fps, there is enough energy and momentum available and it is likely that the petals will tear off, leaving a flat fronted cylinder shape. This ensures good wound formation as the bullet expands and maximum penetration with the cylinder shaped shaft. It is not uncommon for the petals that are torn from the nose of the bullet to penetrate as deep as the shaft.
The pictures below are of a .458" 450gr HV bullet fired into the water tank at the Ballistics/Forensic Laboratory in Port Elizabeth. Velocity was 2500fps.
Further, HV bullets are designed according to the findings of the latest research on terminal bullet performance. This is contrary to the traditional "perfect double caliber mushroom and 100% weight retention" theory. Research done by Duncan MacPherson and documented in his book "Bullet Penetration - Modelling the Dynamics and the Incapacitation Resulting from Wound Trauma", supports the observations we made during field testing of the HV concept.
It has been proven that a high velocity flat fronted cylinder shape will leave a larger primary wound channel than a slower, double caliber mushroom. HV bullets are therefore designed to start mushrooming reliably from much lower speeds than most other premium bullets, typically from around 1000fps. Two to four centimeters of penetration is all that is required to fully expand an HV bullet.
At higher speeds, HV bullets will lose the petals entirely, shedding 12% to 20% of weight and presenting a flat cylinder shape to the direction of movement. The HV concept thus offers, at worst, a good double caliber mushroom, with extremely high retention and, at best, a high speed cylinder shape for dramatic primary wound trauma and deep penetration.
Below left are photographs of a 95gr .264" HV bullet, fired into foam saturated with water. Muzzle velocity was 1900fps and resulted in complete expansion and 60cm (24") of penetration. On the right is a .284" 130gr HV bullet fired from a 7mm RM at a muzzle velocity of 3300fps. The bullet penetrated 120cm (47") on a kudu.
|Photographs courtesy of Alvaro Mazon - Spain||Photo courtesy of Fritz Luttich - South Africa|
I shot two whitetail deer at approx. 160 and 215 yards. Both dropped like stone. Neither shots were spined but both dropped like they were. Both shots were high, being near the apex of the trajectory, but the closest was about 2.5 inches from the spine. Have you heard of this before with your bullets? Do you think the velocity could cause hydraulic spine damage?
What you have experienced is classic HV performance. When we started down the road with the HV design, we noticed that the faster we drive the bullets, the more dramatic and the more frequent were the incidents of one shot knockdowns. With no bullets recovered from game in the initial testing phases, we assumed that the bullets mushroomed and had extremely high weight retention, as that was what our HP range was doing. We also noticed that the softer (easier to expand) we made the HVs, the better they worked at all distances on game. All along we were puzzled by the fact that exit holes appeared to be only slightly bigger than calibre size. Close shots produced bigger exit holes but meat damage was still less than what we expected, given the speeds we were getting.
Then, in fairly quick succession, we were confronted by some very strange facts. We recovered a number of small calibre bullets from large animals where the bullets worked extraordinarily well. All of them were the same shape. The petals were completely torn off and the bullet front was expanded to a virtually flat shape. Weight retention was around 80 to 85 %. Experimentally, we then designed some hard bullets and some soft bullets and went shooting animals.
In every instance where we had double calibre or more expansion with full weight retention, the effect on the animal was less dramatic than with the "soft" bullets that broke down to 80% or so. To add to the confusion, our FN bullets were becoming an unprecedented success. Wound channels from the FN bullets resembled those of soft nosed premium bullets that expand to double calibre and more.
Clearly something was better about the soft HV design and the FN flat nose.
For someone like me with forty years worth of input that said "good mushroom, maximum weight retention" it was impossible to figure out.
The results were indisputable though, and the HV concept was born. While we designed HV bullets that would go as fast as possible, completely expand in one to two inches, throw off the three petals and then carry on as an expanded cylindrical shape, we searched for an answer to explain why the effect was so dramatic.
The explanation came in the form of an excellent book by Duncan MacPherson - "Bullet Penetration". His research reveals a couple of things:
1. It removes all doubt that the most valuable wound trauma incapacitation mechanism is a single large wound channel.
2. It proves conclusively that the most reliable instrument with which to inflict the maximum amount of disruption was a vertical faced, sharp edged projectile.
The reason why a cylinder shape is so much better than all other is because of the manner in which it displaces the tissue it encounters.
A rounded shape of any description displaces tissue to the sides of the wound channel in the time it takes for the front of the shape to move forwards and be replaced by the full width of the shape, creating a primary wound channel. Although this happens very, very fast, a rounded shape therefore contains a time and distance element that translates to a level of force imparted to the tissue. This makes the tissue continue to stretch away from the bullet path, creating a temporary wound channel, until the elasticity of the tissue overcomes the force and brings it back to the original position. Some of the tissue would have been disrupted and this would add to the total size of the primary wound channel.
A cylinder shape encountering tissue, displaces the tissue to the side vastly faster on a time/distance basis than any other shape. This imparts a far higher force to the tissue, pushing it much further from the primary wound channel, disrupting more tissue beyond the limits of elasticity and ultimately contributing to a much bigger primary wound channel.
Now there was clarity about the FN bullets as well. The HV design was in fact only an HV in flight. A couple of inches after impact, it would resemble an FN bullet.
In practise we see with HV and FN bullets that soft aqueous tissue such as the lungs, liver, brain, large blood vessels and stomach contents suffer massive trauma with HV and FN bullets. Firmer tissue such as meat, heart and kidneys survive much better.
Another point MacPherson mentioned in his findings was that, when the larger temporary cavity included a vital element, such as the liver (or spine in the case of your two shots), the damage to those elements was enough to cause disruption and incapacitation.
The bottom line is that traditional bullets, that depend on a mushroom, may or may not work. In some instances they break up too much and fail to penetrate deep enough, and sometimes the forces are not high enough and they do not expand at all. With HV bullets the worst that can happen is a good mushroom, if speed falls to really low levels. At speeds over about 2600 fps, the petals part company and it turns into a totally reliable mechanism that works in the same manner with monotonous regularity.
A 200gr .338 HV bullet fired from a 340 Weatherby at 3350 fps. It penetrated the full length of a kudu, from the entrance wound on the back leg to the lower edge of the jawbone, where it was recovered. Impact speed was over 3000 fps.
A 130gr 7mm HV bullet recovered from a kudu. Impact speed, fired from a 7x57, was 2580 to 2630 fps. The bullet entered in front of the shoulder on the quarter frontal shot and was recovered from the ribs on the opposite side.
GS Custom Bullets, situated in Port Elizabeth on the East Coast of South Africa, manufactures solid copper, turned, monolithic bullets for hunting and sport shooting. These bullets are used by hunters on several continents, hunting from the smallest of antelope to the largest of dangerous game, using the smooth HP bullet, as well as the more popular HV, FN and SP bullets with the patented drive band concept. GSC bullets are configured for the highest possible ballistic coefficients. SP bullets are mainly used for sport shooting. All GS Custom Bullets are coated.