The Secrets Behind the Killing Power of TSS

The Secrets Behind the Killing Power of TSS

Many hunters are curious about Tungsten Super Shot (TSS), but they wonder whether it's worth the cost and how it performs. TSS is the most effective, but also the most expensive, bird shot ever engineered. Its density of 18.1 grams per cubic centimeter (g/cc) allows ammo makers to load more, smaller-sized pellets in each shell than any other shot type, adding to its downrange effectiveness.

Tungsten is also an incredibly hard metal, requiring steel-type shot wads that protect the inside of your shotgun’s bore from scoring. An advantage of that hardness is when TSS pellets exit the muzzle they experience little to no deformation. Softer lead and bismuth pellets can deform or fracture, which can result in inconsistent patterns.

And since TSS pellets are smaller, they reduce wind resistance and will not lose velocity as quickly as larger pellets. All that adds up to more pellets on target that hit harder than any other non-toxic or lead shotshells on the market. But you do pay for that performance.

A single shell of TSS for a turkey, waterfowl, or upland hunter can cost as much as $10, an expensive limit of ducks even if you shoot one shell per bird. Comparatively, Hevi-Shot (12 g/cc) is around $4 per shell, bismuth (9.7 g/cc) is $1.75, lead (11.7 g/cc) can retail for less than 50 cents per shell, and steel loads (7.8 g/cc) are $1.30. Steel is still the most popular option for duck hunters, and most upland hunters continue to rely on inexpensive lead offerings. However, there is a massive uptick in the number of turkey hunters that employ TSS, likely because you only need to shoot once (hopefully) to kill a spring tom.

Understanding TSS Pellet Size

If you are a waterfowl, upland, or turkey hunter, Nos. 7½ to 10 shot will anchor just about any bird, though you may need to steer toward the larger end of that spectrum on late-season mallards or Canada geese after they develop their down feathers. Predator hunters can shoot BBs, 2s, or 4s, and hog and deer hunters (where legal) will use BBs. A common rule of thumb for TSS load developers is to take lead shot and reduce it by two to four sizes. So, a turkey hunter that typically shoots a No. 4 or 5 lead load can shoot TSS No. 9s.

The U.S. Fish and Wildlife Service once conducted a test in which over 4,000 mallards were shot in a controlled environment with a variety of loads. At the end of the study, it was concluded that an energy density of 235 ft/lb./inch squared killed ducks more than 95% of the time. Energy density is a complex scientific measurement I won’t go into great detail on, other than to say it is a tool that gauges the amount of energy needed at the target to dispatch quarry.

Ballistics software has shown that a No. 9 TSS pellet with a muzzle velocity of 1,550 fps will generate 348.2 ft/lb./inch squared of energy at the target when shot from 40 yards. Comparatively, a No. 4 lead pellet with a 1,350 fps muzzle velocity generates 291.1 ft/lb./inch squared of energy at the target from the same yardage. That’s a fairly wide gap in performance. Also, consider that 355 pellets are in a 1-ounce payload of No. 9 TSS as opposed to just 170 pellets in a 1¼-ounce lead load. There are far more projectiles, hitting the target harder downrange with the TSS offering.

TSS Is Not Safe For Every Shotgun

Most shotgun barrels built before the 1980s did not account for the hardness of steel shot or TSS, so they may be unsafe for tungsten-based loads. Shooting TSS through an older shotgun could damage the barrel or choke tube.

Talk to a gunsmith to make sure that the gun can be used with TSS. For instance, TSS should not be shot through a Belgian-made Browning Auto-5 barrel, but the Japanese variant of the Auto-5 has a stronger steel alloy barrel that is safe for TSS.

TSS Load Development

When it comes to loading TSS, the engineers at Apex Ammunition are some of the foremost authorities in the U.S. I’ve talked to them at length about the development of TSS, which Apex popularized (many hunters were hand-loading it themselves as well) before the larger ammo makers started producing their own offerings.

TSS (and other non-toxics that are denser than steel) have really energized the small-bore revolution. But it’s a balancing act to pair bore diameter, payload weight, and pellet size all together. Apex has found that the largest pellet for 10- and 12-gauge is BB, No. 2s for 16 and 20 gauges, and 4s for 28-gauge. In .410-bore, No. 7½ shot is as big as you can go unless the pellets are stacked perfectly. If you don’t follow these loading rules, a phenomenon known as “bridging” can occur. Bridging happens when two or more pellets interlock as they travel down the barrel. If the shot is as hard or harder than the barrel (TSS, Hevi-Shot, and steel all are) it can damage the gun and choke tube.

Because TSS is so hard, loads with smaller pellet sizes (7½ to 10) require a polymer buffer (they look like clear pellets). If the buffer is not there, the pellets will bounce off one another and pattern percentages suffer. Larger TSS shot does not need a buffer due to its weight. The pellets are heavy enough that they will not ricochet off each other.

Propellant burn rates are also important to building well-engineered shotshells. The faster a powder burns, the more chamber pressure it creates. Essentially, ammo makers want to create a controlled explosion once the firing pin hits the primer and the powder burn begins. If the rate of burn is too hot, it can create a dangerous amount of chamber pressure (above 14,000 psi). But if the burn rate is too low, the payload will not have enough velocity to create effective patterns.

Also, the kind of game you’re hunting affects the propellant burn rate. Duck load powders will burn hotter because it’s typically cold during waterfowl season. Turkey loads don’t need to have as high a burn rate because most turkey hunting is done during the spring warmup.

Putting TSS to the Test

Before a shotshell can come to market, it must undergo a number of tests. First, it must be determined that the chamber pressure is safe. To do that, a series of 10 shotshells are fired. The evaluator (often an independent third party) uses a piezoelectric gauge—a crystal that emits an electrical charge—to measure the pressure and make sure the shotshells are within SAAMI standards for the gauge.

If the shotshell passes the SAAMI test, it's onto the pattern board. Evaluators shoot the loads through multiple shotguns and chokes from different yardages. Patterns must not fall off more than 10% every 10 yards the gun is moved back from the target out to 70 yards. If the shotshell fails to perform, the engineers must find a solution before it can move on to the next stage.

The shotshell is then put to the penetration test. Evaluators shoot into FBI-grade gel blocks at various distances, looking for wound channel size and depth of penetration in comparison to the tested velocity of the payload. TSS should penetrate the ballistic gel between 3 and 6 inches. Some larger TSS shot will penetrate even deeper.

Finally, testers take to the field, making sure the shotshell performs in the conditions it was intended for. Waterfowl loads are shot repeatedly in the cold weather duck hunters often encounter. Evaluators want to see that the burn rates of the powder are adequate so that the shotshell maintains proper velocity and patterns optimally. Turkey propellants typically don’t burn as hot, so they may not fare well in frigid temperatures.

While we can't guarantee that switching to TSS will bag you more birds, it could increase your odds. At $10 a round, it’s likely not worth shelling out the dough for waterfowl season. It could make a difference when you have a big tom in shooting distance, but it won’t make up for bad hunting.

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