Low-speed heavy bullet expansion

I was pondering my earlier experience with bullet performance, and got to wondering about the other end of things, with low-velocity rifle bullets. When shooting at very long ranges, or when using a subsonic cartridge like a 300 Blackout / Whisper, what heavy .30 cal bullets expand reliably at around 1000 fps? Obviously something like a 200 grain Nosler Partition will hold together, but will it mushroom at all at low velocity? They only brag about expansion down to 1800 fps on their Ballistic Tip, which only goes to 180 gr. Their “long range” Accubond recommends greater than 1300 FPS. Now, with a BC of .730 in a 210 gr Spitzer it’s still going to hurt what it hits, but if you want to maximize energy transfer, punching a neat hole isn’t the way to do it.

Any thoughts, experience, recommendations, or rumors?


9 thoughts on “Low-speed heavy bullet expansion

  1. Haven’t tried it in .30, but .45-.50 cal. Pure lead works surprisingly well. Extremely ductile, Not moving fast enough to come apart completely. Expands like crazy. Only bullet I’ve seen recovered from an animal was a 400 grain 50 cal fired from a muzzleloader. Diagonal shot through 3 feet of deer, A shoulder and several ribs. Pretty much the whole surface was beat up and there were some bone fragments embedded. It had turned sideways at some point and was about 5/8′ X 1″ and only lost 20 grains weight. Bullets recovered from berms were similar – Lots of deformation with little weight loss.

    Downside is they’ll probably need to be paper patched to not lead up the bore horribly. And that is more than a bit inconvenient.

    • I’d be reluctant to try pure lead in a semi-auto, which is what prety much all the 300 Blackout / 300 Whisper rifles are (usually AR uppers), even with a paper patch.

  2. A cast bullet, made of Lead:Tin, about 16:1. Tin “toughens” rather than hardens the alloy, unlike Antimony. It expands, but the mushroom doesn’t break up and detach. You can go higher on the Tin, but at subsonic speeds I don’t think you need to.

    You shouldn’t need a paper patch at subsonic speeds, just a well designed bullet with an appropriate lube. I don’t think your silencer would like the chaff the paper jacket becomes! And if you’re not using a silencer, why in hell would you be wanting both terminal performance and a subsonic projectile?

    As far as semi autos and cast bullets being a bad idea, I shoot mostly gas checked cast in my Garand. No problems, and I’m usually running near 1800fps.

  3. I don’t know if this has any value for what you want to do, but I’ve been digging into 300 BLK some, and for short range / thin skinned problems, heavy bullets may offer some promise. For example, the 240 grain Sierra MatchKing HPBT (.308″ dia, 1.59″ length) – according to load data, it can be driven at barely supersonic velocities (about 1150), and in a slow twist barrel (1X10, 1X10.5) at that velocity it won’t stabilize well, and should tumble on impact. MatchKings have heavy jackets so it should hold together as it tumbles. At 1150 it’s got about 700 ft/lbs energy which isn’t a lot, so tumbling it may not penetrate much. The sweet spot may be around 190 grains (1500 FPS, 950 ft/lbs), maybe 165-180 gr at 1600-1850 (165 @ 1850 energies out pretty close to 55 grain 5.56). At those velocities I think trying for tumbling would be better than hoping for reliable nose expansion. Sounds like some experimentation is in order.

    • My understanding about the tumbling effect is that the bullet just wants to swap ends when entering a fleshy medium. So it does a 180, takes some distance to reverse ends, and then continues its path backwards – that’s for anything from a 5.56 FMJ to a 7.62×54 FMJ. It isn’t as if the bullet turns into an eggbeater – it just yaws a half turn.

      An effective expanding bullet would definitely be preferred.

  4. Lee makes a 5 radius ogive cast bullet mold in 230 gr especially for the 300 Blackout. In soft lead, that should expand reliably in tissue. I wouldn’t expect anything with a copper jacket to expand reliably without a serious hollow nose cavity. If you chuck match bullets into a lath and open up their tip, this will work, you’ll lose a little mass, but not enough to matter at any range you have engaging something with a 300 Blackout.

    • Hmmm. Interesting. 230 gr 30 cal mold. Might be worth looking into. Not that I really want to get into bullet casting, but get into it enough to cast a good set. Reviews are good, and it’s in stock. Using Bert’s 16:1 Pb:Sn mix might be nice, too.
      If possible, though, I’d like to get ready-made bullets, perhaps Hornady A-Max.

  5. I was just looking for 300 BLK/Whisper ammo the other day. One of the manufacturers – I believe Hornady – is starting to market subsonic ammo that they claim is designed for expansion. Out of stock, of course.

  6. I have been playing with Berger bullets trying for the most accurate hunting load. Their hunting/target hybrid bullets claim basically disintegrate upon impact with limited penetration. Now I am playing with .308 Winchester and 243 Winchester loads and YMMV.

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