SMKs, unaltered, tend to be very unreliable in most calibers. The cavity isn't that large under the meplat and ahead of the core to begin with on them, and the opening is also typically pretty small and sometimes jagged and can create inconsistent and unreliable expansion. I used to use them a lot at one point, and found drilling the tips and going slightly into the core with a 1/16" bit widened the meplat and increased the cavity enough to produce very reliable and consistent results. I later upgraded the process to a meplat trimmer and widened the tips to .070-.100" depending on caliber. It worked just as well and was more efficient than the drill bit, plus more consistent since there's a degree of error involved in drilling them.
Once I started using AMAXs, then ELDMs, and then TMKs, I stopped bothering with all that and just shoot those now. No loss in BC and no extra steps and tedious work at the bench.
If corrected like I mentioned though, the SMK has around a .026" thick jacket, just like the GameKings and TMKs, and they'll work well down to 1400fps with a good amount of impact resistance. For a shot like behind the shoulder on a whitetail, I'd maybe be more confident keeping it no lower than 1600fps though just due to the smaller cavity.
And yes, uncorrected/unaltered, they can and have still worked great for a lot of people, myself included. They've just had instances where they didn't open up properly though too and that's the unreliability and inconsistency I'm talking about. Correcting and widening the meplat will fix that, or using a tipped bullet
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Also, in regards to the 175 SMK specifically, it's used in M118LR and is made to consistently not be "inhumane" per the Geneva Convention and Hague Declaration. A lot of testing went into it and it's use as a sniper round in the DoD. It's still highly advised to open the tips up in order to ensure reliable expansion time after time, especially when impact velocities dip below around 1800fps. They're typically better than other SMKs, but I've found a lot of newer lots of SMKs across calibers are a lot better than they used to be.
Also, I do have a few posts related to things like this and showing differences in jacket thicknesses and construction, found here:
https://www.longrangehunting.com/threads/bullet-construction.283735/
https://www.longrangehunting.com/threads/selecting-a-hunting-bullet.283902/
https://www.longrangehunting.com/th...d-in-comparison-to-other-bullet-types.283812/
https://www.longrangehunting.com/threads/berger-hybrid-vs-berger-vld.283905/
Also, I've not read through this whole thread, so my apologies if I missed something or echoed anything.
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