Let’s talk about monolithic bullets! Also known as homogenous bullets, they’re entirely constructed out of one material, usually cooper or a cooper-zinc alloy. For the purposes of this post we’re going to stick to the performance of the projectile down range, on the animal and leave the politics & environmental concerns out of it. We’re strictly talking performance.
When it comes to performance monolithic bullets offer one distinct advantage over other bullets in its class, penetration. A secondary and somewhat more debatable advantage is reliable expansion.
Monolithic bullets achieve their legendary penetration from their inherent ability to retain weight. This is due to the fact that these bullets tend to retain their size and shape far better than a comparable lead core projectile. Depending on what you’re trying to achieve, weight retention in a bullet can be a pro and a con. If you’re hunting varmints, it could be considered a con. If your hunting moose, deer or elk it could be considered a pro. When thinking about this comparison it’s important to remember that there’s no free lunch in physics, when a bullet penetrates to the point it leaves the animal you’ve effectively left some amount of energy on the table that otherwise could have been transferred to the target. If the speed of the bullet exiting the animal were a known value we could calculate that energy exactly. For most hunting situations, especially in Maine, the trade-off between penetration and energy transferred to the target is usually a one sided one. Typically a hunter in the Maine woods would rather have two holes in the animal, an entrance and exit. This leads to easier tracking due to the larger blood trail. On the other hand, sheep hunters in the Rocky mountains tend to prefer bullets that expand significantly and therefore “dump” all of their remaining energy into the animal. When everything else remains perfect this tends to lead to an immediate incapacitation of the animal, dropping it in its tracks. Meaning the sheep remains right where you shot it, which means if you took a responsible shot that sheep would be in an accessible area and not deep in an inaccessible cavern or cliff face. Two bullets for two different jobs.
Other factoids about Monolithic bullets:
Lead cores tend to be more accurate, at least to hunting distances out to 300 yards and beyond. This is because of the higher Ballistics Coefficient (BC) achievable in lead core bullets over monolithic.
Ever wonder why monolithic bullets have 3 and sometimes 4 relief groves cut into them? That’s to cut down on copper fouling on the bore of your rifle. The grooves allow a place for the copper material to flow as the bullet is formed to the rifling rather than be deposited in the bore of your rifle.
Copper bullets can be limited by velocity dependent expansion. Again, because the copper is a harder and a more dense material they resist expansion more than a comparable lead bullet would. Because of this a responsible hunter should research at what velocity parameters the mono bullet he/she is shooting was designed to reliably expand at. This velocity then can be applied to the particular load/rifle you’re shooting it out of to determine an effective maximum range you can ethically take a shot at. Lead core bullets offer a much more forgiving velocity range that the bullet will reliable expand, this is why copper bullets are typically not used at what would be considered a long range hunting scenario.
Monolithic bullets tend to be much lighter weight projectiles (for caliber) than a comparable hunting “style” lead core bullet, one reason is that copper is a less dense material when compared lead, meaning a copper bullet needs to be physically longer than a similar lead bullet to achieve the same mass. This “eats” into the powder column in most cartridge cases and can limit the velocity ceiling that’s achievable out of both factory and handloads.
Another factor as to why copper bullets are typically on the lighter side is because when compared to a soft lead core bullet the less malleable copper induces a greater initial pressure as the bullet is forced into the rifling. Pressure reduction comes at the cost of bullet mass.
Overall, I think monolithic bullets offer the best of both worlds, especially for the typical Maine hunter. Over all else most Maine hunters would rather have reliable expansion with a tough bullet that can penetrate bone and whatever else stands in its way while leaving a decent blood trail to track the animal in the thick Maine woods when a quick shot at a running deer can be the norm. Especially when compared to western hunting.