Heavier or faster?

[Loosedhorse]

I tend to go with the bullet weight that the round was designed for.
In the .45 acp, that would be 230 gr.
In the 10mm, that would be 180 gr.

As MachIVshooter says, the "original" 10mm load from Norma was a 200gr bullet (but they also had a 170). I think the FBI introduced the 180 in its 10mm "Lite." So those who like the Lite load might want to use that 180 at 980 fps (or just buy a .40)--that's the "standard 10" loaded by many ammo companies.

But the load that the round was "designed for" was 200 gr at 1200fps; and Cooper's original idea was a 200 at 1000fps.

But I'm not sure any of that matters. The load the .357 Magnum was designed for was a 158 gr semi-wadcutter; I don't think this is the .357 load that most of us would choose for self-defense. So, the "load the round was designed for" may be a bad reason to choose a bullet weight. I sure think so.

 

[gofastman]

I think the 180gr XTP moving along really quick is about the perfect SD load for the 10mm, at least at a reasonable price.

180 gr. @ 1,350 FPS for 729 ft/lbs. penetrates 14"

220 gr. @ 1150 FPS for 646 ft/lbs., penetrates 20"

I think you'd get a bit more penetration out of the XTP's than that.

Id throw out:
180gr = 18" of bare gel
200gr = 22" of bare gel

 

[G29]

I appreciate the responses!

 

[Tallinar]

I haven't done a lot of research on the matter, but I am a little surprised to see so many folks advocating the lighter, faster bullet for SD.

It's my understanding that the original .45 ACP loading of a 230gr bullet at around 800-850 fps seems to have performed well - or the blackpowder loading of a 255gr bullet around 950 fps in .45 Colt for that matter. Seems to me that as long as you're not using FMJ, you would be fine at those weights/speeds as far as over-penetration is concerned.

I guess I haven't encountered much reading about over-penetration being an observed issue with 230-250gr bullets at less than 1000fps. If anyone could direct me to some good literature involving this, I would appreciate it.

 

[Loosedhorse]

Back when the .45 Colt was state of the art, we didn't hear a lot about overpenetration, but that doesn't mean it didn't happen. The tests I've seen routinely list about 18" of gel penetration for nonexpanding .45 Colt rounds going about 900fps.

The 10mm lite (and the .40 that came from it) is a good round. If you want to make it better, you can increase the speed (and increase your recoil), or increase your speed AND decrease your bullet weight. A 135 at 1300 fps should recoil about the same as a 180 at 980.

The 155 gr (157, actually) 10mm has about the same sectional density as the 125 gr .357, so going that light (at least) shouldn't be a problem for SD. And with newer bullet techologies (like all-copper HPs that don't shed weight), you can achieve the same depth of penetration of conventional HPs while using a lighter bullet that still expands fully.

Then the only questions that remain are how much penetration is enough/too much; how much recoil is enough/too much; and how much cost is enough/too much.

 

[ATLDave]

Another way to think about this is that the heavier bullet will have a higher sectional density. That will mean that it penetrates more. As others have noted, how much penetration you want will depend on what the circumstances are.

For home defense, or urban/suburban civilian carry, in a relatively warm climate, I'd tend towards relatively light and fast. That way, you get very reliable expansion, but little risk of shoot-through, and you have a chance of a barrier taking enough out of a missed shot to save some third party's life. The chances are better than even that, if a bullet from my gun hits a car door, I want the bullet to not perform well on the other side. I'm not supposed to be out hunting down trouble, only handling that trouble that's coming right at me. If I were a LEO, or lived in a very cold climate, or lived in the woods surrounded by bears or other large, dangerous animals, I'd probably move towards the heavier end of the spectrum.

In all fairness, a 10mm load at anything like full pressure ought to be plenty, regardless of how you've made your speed versus mass tradeoff. It can be on a different power band than the 9mm-.40-.45 spectrum. Remember that even a light&fast 10mm load (like a 155 gr.) is still heavier and bigger around than even the heaviest 9mm, and even a heavy 10mm is going to be faster than a .45 (and should therefore expand pretty well, perhaps even exceeding the .45 in final diameter).

 

[winter1857]

Physics: Velocity diminishes; mass is constant.

 

[tipoc]

The actual weight of the bullet is less a factor in penetration than is the type of bullet being shot. Meaning that bullet construction makes the dominant difference. A 180 gr. FMJ 45acp round will out penetrate a 230 gr. JHP in virtually every medium being fired into if the jhp expands as it should.

Select the bullet type that fits the job. elect the weight and velocity that you can handle well from the gun that you have chosen for that job.

tipoc

 

[MachIVshooter]

I haven't done a lot of research on the matter, but I am a little surprised to see so many folks advocating the lighter, faster bullet for SD.

Lighter and faster, but not really "light and fast"; 180 is just a good bullet weight for the 10mm in the 1,200-1,400 FPS range, providing excellent expansion and good penetration (12"-15").

Physics: Velocity diminishes; mass is constant.

And? No matter the bullet you choose, it is going to slow down. The greater momentum of heavier projectiles will tend to make them penetrate deeper all else being equal, but momentum still drops with velocity (Momentum=Mass*Velocity).

The point remains that 180's provide a good balance in this chambering. I say again, the ideal load is one that will penetrate adequately and use the rest of it's energy expanding the bullet.

Think of it this way:

If you're trying to make a fast 1/4 mile car, you want to balance your gear ratio with your torque and horsepower. You want to cross the line at the top of your power band in top gear. Gears are too tall, you get off the line slow and don't make good use of peak power in the last part of the run. Gears are too steep, you run out of RPM and are redlining the engine the last couple hundred feet, not accelerating thus losing ET. Bullet selection is no different; Too heavy, you overpenetrate and don't make the most of your available energy. Too light, it uses everything up too soon and fails to get to the vitals.

 

[tipoc]

Sometimes folks may think too much.

If we have two 10mm jhp bullets intended for self defense one at 180 gr.s and one at 200grs both going about as fast as you may want them to, they will both penetrate and expand to somewhere between 10-14 inches in 10% ballistic gelatin. Let's take a 10 mm jhp round at 220 gr.s and it also will penetrate to about 10-14". The velocity is irrelevant they will about all do it (there may be a couple that go deeper but mostly they will stay about the same).

No mystery here, it's just that since the late 1990s the FBI figured that that was the depth of penetration that they wanted in defensive ammo and the ammo manufacturers have worked hared to provide that across a variety of calibers.

tipoc

 

[clang]

I bet either one would ruin someone's day. Try them both out and see which one you shoot more accurately and quickly.