The 25-06 retains a tenacious popularity among big-game hunters despite regularly being labeled marginal by scads of modern shooters. The cartridge’s loyal fan base no doubt includes plenty of hunters who live in places like California, where an absolute ban on lead projectiles was instituted on the guise of saving endangered condors from extinction. The logic follows that condors greedily ingest lead fragments left behind from field-dressed animals and are poisoned. This is based on a 2008 California study reporting a handful of sick or dead raptors, in contrast to many more killed annually by green-energy windmills.

Rules are rules, and no one wants a game violation and possible suspension of hunting privileges. But legality aside, non-toxic bullets can include real advantages. This is especially true of “marginal” cartridges such as the 25-06 Remington. Turned monolithic gilding metal or pure copper bullets (turned brass bullets, like those from Cutting Edge Bullets, contain trace amounts of lead, so they are not legal in California) are of the most interest to big-game hunters. These were introduced by former Barnes Bullets owner Randy Brookes and eventually refined via pressure-relief/fouling-reduction grooves and copper alloys less prone to fouling. In my estimation, adding polymer tips creates more reliable expansion while boosting BCs.

Copper is obviously lighter than lead, so same-profile copper bullets will always weigh less than lead-core examples. Though this is true, Neil Emery, Hornady’s long-time ballistician, once pointed out that the controlled-expansion qualities of an all-copper slug, which typically retains 90 to 95 percent of starting weight, give copper bullets a 20-25 percent performance advantage over same-weight or slightly lighter lead-core projectiles. This means that an 80- to 90-grain monolithic might provide the terminal performance of a 100-grain lead-core slug and a 100-grain, the killing properties of a 120-grain lead bullet. This is in play while also gaining a lighter bullet's higher velocity and flatter trajectory, often including a ballistic coefficient (BC) in the same ballpark.

A few important notes are indicated before we begin. Monolithic bullets generally include longer bearing surfaces than traditional cup-and-core bullets of the same weight, despite the aforementioned pressure-relief grooves. This can cause increased friction while moving down the barrel, hence, higher pressures. Companies like Hornady, for instance, generally offer load data specific to their monolithic copper bullets, like the GMX and newer CX. Some monolithic designs are more susceptible to pressure spikes than others, so when using non-monolithic load data, always start conservatively and increase powder charges in slow increments while carefully watching for pressure signs. A longer bearing surface can also mean that the same-weight copper bullets may not fully stabilize in your rifle’s classic rifling twist.

Monolithic bullets are often noted for being frustratingly finicky. This isn’t universal to every brand, but it crops up frequently enough to warrant the stereotype. In this test, for instance, group averages were higher than this rifle typically assembles using proven lead-bullet loads. Copper is harder than lead. The traditional approach of seating lead-core bullets to almost touch the lands doesn’t always provide top accuracy with copper. It is believed by many that seating copper bullets so that they must make a slightly longer jump into the lands helps the harder material better “seat” into the rifling, providing more consistent accuracy. Also, the sharp edges of milled pressure relief grooves often catch on case mouths. A hard chamfer – a 10-count approach instead of five, for example – can help mitigate mouth creases and dings that might prevent a round from chambering.

Bullets chosen for testing covered the gamut of uses, from stout mountain mule deer or Midwest whitetails to those I would confidently use on bull elk, with well-placed shots, obviously. Cutting Edge Bullets’ 90-grain Copper Raptor, Hammer Bullets’ 95-grain Hammer HHT, Badlands Precision's 95-grain Bulldozer2, McGuire Ballistics’ 95-grain Copper Rose and Lehigh Defense's 102-grain Controlled Chaos were chosen for testing.