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Understanding Mono-Metal Bullets
Testing today’s best mono-metal bullets for velocity, expansion and penetration. Are they right for you?
I squeezed the trigger and a millisecond later dust flew from the big wildebeest bull’s hide. Its rear legs kicked out in reaction to the impact and its tail whipped frantically as it bolted from the herd. Guy Swart, my Professional Hunter (PH), was feverishly demanding I shoot the bull again. I was very confident in my shot but obediently racked another round in the chamber. At that point the old bull went into a blind-eyed stagger — but just seconds from total collapse it unbelievably got control of itself and settled down into the dust under its own power. Sure I wouldn’t reach it in time I nonetheless hurried over to finish the job. Amazingly as I drew within 60 yards of what I thought was a dead wildebeest, it raised its head. I sent a second 185-grain GMX bullet from my 338 Win Mag smashing into the boiler room.
Guy came to me and said, “Here in Africa the trackers believe the wildebeest is born sick and every time he gets shot he gets a little bit better.” We had a good laugh over the native folklore but it was easy for me to understand why the blue wildebeest is called the poor man’s Cape buffalo.
Get The Lead Out
Lead free bullets — sometimes called mono metal bullets — have become very popular in the last few years. Mono metal, however, is a bit of a misleading term. In actual fact a solid lead bullet would be considered mono metal. As would a bronze solid used for hunting elephants or Cape buffalo. However, when I use the word’s mono metal in this article I’m talking about bullets that are composed of either copper or copper alloy.
Mono metal bullets first came about as a unique way to control expansion and bullet performance. The major problem of core and jacket separation on lead core-based bullets is pretty much solved today with the advent of bonding. Bonding is when the lead core and the gilding metal jacket of the bullet are chemically or physically bonded together. But in today’s world, lead has fell on hard times and it is considered a health hazard. Lead has been branded by studies showing animals dying from ingesting lead pellets or fragments. California champions the charge by passing a law banning lead and lead containing projectiles for all areas frequented by condors. Soon, the rest of the state will be lead-free as well and other jurisdictions are starting legislation looking to follow. Human health concerns were raised by a surprising study done by the Minnesota government, which detailed lead dispersion from bullet impacts in animal carcasses — another driving force behind lead-free bullets.
Environmental concerns aside, mono metal bullets are incredibly durable and really shine when the going gets tough. With no soft lead core to fragment, distort or separate, mono metal bullets can take impact speeds that absolutely destroy conventional style bullets. With a homogeneous construction, expansion is carefully controlled. These bullets usually expand one–and-one-half to twice their original calibre and very seldom shed any weight. Weight retentions of 95 per cent and above are common. A catastrophic failure of a mono metal bullet would be shedding all of its petals. Even at that, the bullet would still retain about 85 per cent of its original starting weight. These bullets were designed for deep penetration, for smashing through bone and muscle and tissue at speeds that destroy lesser bullets.
Conventional lead core bullets perform well at sub 3,000 feet per second (fps) velocities, above that velocity bullet design becomes critical. The trend to high-velocity cartridges or the use of light-for-calibre bullets in search of higher velocity in the 1960s, ‘70s and ‘80s played havoc with conventional bullet designs. As long as the impact was far enough away from the muzzle, the old technology bullets would work. But if you have 140-grain bullet smoking along at 3,500 fps from the 7mm STW run into a deer’s shoulder at 40 yards and you had a recipe for a catastrophic failure — and a mess.
Today there are three major manufacturers of mono metal bullets. Barnes is the oldest by quite a margin followed by Nosler and the most recent entry Hornady.
Randy Brooks is the genius behind the Barnes solid copper bullet. Mono metal bullets came of age when in the spring of 1986 Randy successfully used a 270-grain X Bullet from a 375 H&H Magnum on Alaskan brown bear. The bullet was made of 99.99 per cent pure copper had an impact extruded hollow cavity in the nose and was scored so that it would open into four petals forming an X, hence the name — X Bullet. The all copper bullet was plagued with reports of excessive copper fouling in barrels.
In 2003 released the TSX, a new bullet with four annular grooves around the shank. As the bullet travels down the barrel and the copper deposits on the rifling the groove allows the freshly deposited copper to scrape off in the groove. Grooves on the shank meant there was less bearing surface between the bullet and the rifling, greatly reducing friction and pressure. The grooves greatly increased accuracy of the bullet and created a huge increase in the number of rifles that shot the new bullet well. In 2007 Barnes followed with the natural evolution and brought out a polycarbonate tipped version of the TSX called the TTSX. With the pretty blue tip came a larger hollow cavity. The theory is the blue tip acts as a wedge to initiate expansion as it strikes the target. Barnes makes the TTSX in 15 calibres and a multiple of weights in just about every calibre.
Introduced in 2008 the E-Tip is a joint venture between Winchester and Nosler. The bullet is constructed of a copper alloy rather than pure copper. Ninety-five per cent copper and five per cent zinc is an alloy commonly called gilding metal. Gilding metal is used for constructing bullet jackets in conventional bullet construction. The five per cent zinc increases the tensile strength of the bullet while acting as a lubricant.
Copper fouling with the E-Tip is no different than copper fouling with any regular jacketed bullet. The E-Tip like all mono metal bullets is extremely durable, Nosler claims 95 per cent weight retention, and it penetrates deep. Reliable expansion has always been an issue for copper or copper alloy bullets. Nosler uses the combination of a polymer tip situated over a dual chambered expansion hollowpoint. Nosler’s E2 cavity or energy expansion cavity works in conjunction with the energy control ring around the mouth of the cavity to provide uniform expansion.
Nosler gives the E-Tip a performance window from 2,000 fps at the lower threshold to 3,200 fps and beyond. Because the bullet doesn’t have annular rings cut into its shank to mess with its aerodynamic profile, the E-Tip as a much higher ballistic coefficient than the comparable bullet in a Barnes TTSX. Selection of the Nosler E-Tip is somewhat limited, with bullet weights available in seven calibres.
Released to the shooting public in 2009, the GMX is Hornady’s foray into the no-lead bullet discipline. GMX stands for Gilding Metal eXpanding, which tells us the bullet is also composed of gilding metal. Hornady uses the same 95 per cent copper and five per cent zinc alloy composition as Nosler does.
In addition to the bullet being made out of solid gilding metal, Hornady also designed two annular rings on the shank of the bullet. Hornady wasn’t looking so much for the antifouling properties of the rings or grooves as much as the ability to efficiently seal the bore — increasing accuracy. The grooves reduce friction and pressure in the long-for-weight bullets. In fact this was one of the design criteria for the GMX bullet, it had to exhibit the same pressure curve is other Hornady bullets — so the exact same powder loads could be used for the GMX as are used for the other bullets. Penetration is never been an issue with monolithic bullets, in fact the opposite is true; very seldom do I get to recover a bullet. The GMX is designed with a red polycarbonate tip to initiate the bullet opening in a six-petal configuration. Six smaller petals open easier and curl back to the shank similar to the way the jacket on a lead core bullet does. This creates greater frontal area and more reliable expansion, especially at the lower threshold velocities. Hornady produces the GMX in eight calibres, bullet weights are on the lighter end of the scale for each calibre.
Range Velocity Testing
I loaded up a bullet from each manufacturer’s lineup in my 7WSM Rocky Mountain rifle and headed out to the range. (One thing to keep in mind while reading this comparative is the fact that each rifle is an individual and each rifle has its preferences as far as bullet type, velocity, powder, etc. All this comparative is going to show is what my rifle likes on a given day.) So take this for what it is: a comparative of how these bullets performed in my rifle.
The bullets I used were the 140-grain TTSX from Barnes, 140-grain E-Tip from Nosler, and the 139-grain GMX from Hornady. I worked up a load for each bullet, slowly increasing the powder charge until pressure signs showed up or accuracy was affected. I played around a little bit with bullet seating depth until each bullet showed a preference. Seating depth varied from 35 thousands of an inch to 50 thousands of an inch off the rifling. These bullets should never be set too close to the rifling; they shoot a lot better with a little jump for a windup before engaging the rifling.
I shot three groups of three with each bullet at 100 yards. Accuracy was good with all of bullets but in particular the GMX shone, with a 100-yard average of .62 inches for the three groups. None the bullets shot over one inch at 100 yards; with the average for each being sub MOA. I shot all the bullets through the chronograph to check for velocity while shooting for penetration and accuracy.
These loads were designed using accuracy and pressure signs as the criteria; nonetheless the E-Tip was substantially slower than the other two as pressure signs on the longer bullet showed up well before they did on the other bullets. What is substantial? Nearly 200 fps on average — nothing that the critter at 200 yards would notice but certainly a factor if long-range is your game. All the loads averaged over 3000 fps muzzle velocity — definitely the hyper-velocity range that mono metal bullets were designed for.
Penetration & Expansion Testing
The penetration and expansion test was frustrating and predictable. I’ve shot many copper and copper alloy bullets into ballistic gelatin before this test so I had a pretty good idea what to expect. The biggest problem is stopping them, especially the TTSX. In fact I never did manage to stop a TTSX and collect it for photography. To my layman’s eye the GMX and the E-Tip have deeper cavities that allow for expansion past the root of the metal petals. This allows for much larger frontal area as once the petals curl back along the shank past the root it creates a frontal surface that is full diameter of the expansion, almost exactly like a jacketed lead bullet.
The Barnes bullet petals are shorter, the edges stay very sharp and the gaps remain between the petals so the total frontal area is reduced. Less frontal area equals less resistance and deeper penetration. Less frontal area can also equal a smaller wound channel and a much smaller temporary channel as the bullet smashes its way through the animal.
My setup to measure penetration and expansion consisted of 35 inches (90 cm) of Perma Gel (ballistic gelatin) followed by a 12-inch (30 cm) airspace then a hanging heavy-duty mudflap off a semi followed by another 12-inch (30 cm) airspace and a last mudflap. I shot each bullet through the setup and other than one E-Tip, all of the GMX and E-Tip made it through the gel to strike the first mudflap and fall to the ground. The one E-Tip made it through the first mudflap and hit the second but not penetrate it. All the TTSX cleared everything and kept on going.
The gel was at the 25-yard mark on the range, I did this so that impact velocities would be as high as possible in order to determine the durability of each bullet. Not a single bullet shed a single petal. I assume it was the same for the Barnes TTSX, as I didn’t find any errant petals in the gel. Expansion on the recovered bullets was uniform and beautiful — both the E-Tip and the GMX expanded to twice the .284 calibre, or slightly more.
There were no surprises brought to light in the testing. These bullets are incredibly durable and penetrate deeply. Perhaps too deeply in some cases, as a front-on shot can both kill the animal quickly and create a stinking mess when the bullet penetrates back into the guts.
Are copper or copper alloy bullets for you? That question can only be answered by the animals you hunt and the cartridge you use to hunt them. If you’re hunting style calls for high impact velocities or tough angle shots on big game than these bullets are definitely your first choice. If you’re looking for a new hunting bullet and are having a hard time finding one your gun shoots accurately — then the new mono metal bullets are most definitely worth a try.
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