Home Forums Hunting & Shooting Ask The Gunwriters Impact velocity and bullet expansion

I have come to the conclusion that I want my game bullets (excluding small game/varmints) to have a muzzle velocity no greater than about 3000 fps. I would rather have a rifle with enough power and size to get the job done with conventional cup and core bullets, then to rely on bullets such as the Barnes', which I must concede, seem to perform wonderfully. The prominent thought here is that when you push the cup and core style bullets to a very high velocity, you risk fragmenting the bullet, ruining meat, and reducing desired penetration. So, to solve this, I simply increase my bullet weight in a given cartridge to meet my own personal standards.

Where I get hazy on the subject is MINIMUM impact velocities that allow proper epansion of a given bullet. I would think that this magic number would change, depending on bullet hardness, design, and construction. So, at what velocities would those of you with an intimate knwoledge of terminal ballistics, consider the minimum impact velocites for cup and core bullets? Partition style bullets? Mono-metals?

A couple years ago I saw a extensive "table" that had photos of a variety of bullets shot into test media at various impact velocities (100 fps intervals for each bullet brand/model - e.g., Speer Hot Cor). I think I saw that table here at the Campfire, and I hope someone will post it again. At any rate, the typical cup-and-core bullets appeared to have a minimum impact velocity (for consistent expansion) of around 1900 to 2000 fps for the test media that was used for the project (some looked like they had decent expansion at 1900 but not at 1800 and some looked like they had decent expansion at 2000 but not at 1900 - depended on brand and product line within the brand). For example, I'm remembering at least one of the Speer bullets looked like 2000 fps was the minimum and at least one of the Hornady bullets looked like 1900 fps was the minimum. However, within the Speer line, the Hot Cor and Mag Tip (which Speer would probably call a premium) might have different minimum velocities, and within the Hornady line the SST might have a different minimum velocity from a comparable BTSP (I don't recall all of the details from the table).

I am not an expert but I agree that over 3000fps weird things seem to happen to normal lead core bullets.

I have found your run-of-the-mill bullets like the Interlock or Core Lokt LOVE impact velocities around 2500 to 2800. This experience is based mostly around the 270 and 308 and to some extent the 222 and 30-06.

For some reason the Hotcor seem to me to be able to take a little more heat and perform well, eg about 3000fps in the 270. Maybe just my perception but it seems a little tougher than the others I mentioned above inlcuding the SST.

What is the experience upon which your conclusion is based?

Impact velocities of 2500-2800 fps is under 100 yards for the majority of hunting rounds!!!

I'm no gunwriter, but based on my reading it seems that most standard lead bullets give pretty decent expansion as long as they impact at around 1500- 1800 fps. Depends on the exact bullet. The solid copper bullets need a bit more speed, 1800-2000 fps.

Some of the bullet makers list suggested maximum and minimum impact speeds on their websites, others do not.

I agree more with JMR is saying. 1800 has been the impact velocity that I have desired, and when I use ballisitc software, I often consider the distance for that velocity about max for that cartridge. I appreciate what you all have had to say.

Here are graphical summaries of some of the data in the great penetration experiment.





The first chart is penetration vs. impact speed for a few common types of bullet. The second is the average of Speer, Sierra, and Hornady. Averaging reduces the random noise, and does a better job of showing the underlying trend.

The lessons of the graphs are:

1. Below a critical speed, the bullet fails to open. That gets you a very long skinny wound channel.

2. Above another critical speed, the bullet opens too much, too fast and either gives you a short fat wound channel, or, more likely, breaks up and gives significantly reduced penetration.

3. Between these two critical speeds, penetration is pretty constant. It doesn't matter much what the impact speed of the bullet is, as long as it is in that range.

4. For standard cup and core bullets, the critical range is about 2100-2800 FPS.

5. Not fully shown in the individual graph, the Barnes X and the Nosler Partition open reliably at around 1800 FPS and penetrate properly up to warp 9.8. They also produce deeper penetration that cup and core bullets. IIRC, Hornady Spire points open around 1800 as well, but I could be mistaken.

Manufacturers will tell you the optimum impact speeds for their bullets.

Wow. According to that graph, the mean penetration really takes a turn at around 2100 fps, which is considerably higher then my original guestimate of about 1800 fps for most bullets. If this is true, and standard cup and core bullets are not expanding at those velocities, then that would limit the ability of particular cartridges and a specific bullet loaded in those cartridges to kill quickly at longer ranges. So, if this is the case, is expansion on game, such as deer, less of an issue as just ensuring that you strike vital organs?
According to my Sierra Infinity software, my 165 Sierra GK leaving my 30/06 at about 2900 fps is dropping below the 2100 fps mark at about 350 yards. This seems short of what that round should be able to reliably kill a deer at. So, does this mean that hitting the heart, lungs, or some other vital piece of anatomy is more important than having a destructive wound channel? If this is the case, why not just hunt with Matchkings???

Man, I need to shoot something.

It's not like the bullet completely quits functioning below 2100 FPS. It just doesn't function as well. I'd sure as heck hate running into a 165 grain cup and core bullet moving 1900 FPS.

If you want optimum performance at 500 yards with that load, then a premium bullet such as the Partition is probably worth the extra cost.

Personally, I won't walk 500 yards to pick up a dead animal. My limit is around 200, unless it's a once in a lifetime trophy. That simplifies things considerably.

That is a very good way of looking at it. Most everything I have killed has been under 100 yards. But, if I look at things this simply, I won't have anything to bs about during the off season.

I think there is a big difference in optimum expansion and adequate expansion. Optimum expansion may be achieved at 2000+fps, but most bullets for modern rifles will still give adequate expansion at slower speeds, 1800 fps or less, in my opinion. Some, such as RN bullets designed for 30-30 speeds will give good expansion at much slower speeds.

Nosler shows some photos of their bullets at various impact speeds. http://www.nosler.com/Bullets/Accubond.aspx. Only the Accubond shows a suggested minimum speed of 1900 fps.

While no speeds are suggsted for the Ballistic tip the photo they show at 1900 fps shows more expansion than the Accubond at 2000. I don't claim to be an expert and if wrong don't mind someone setting me right, but my take is that most standard bullets will most likely do the job as slow as 1800 fps. Maybe not as dramaically as if they impact faster, but still get the job done. The solid copper bullets probably work fine at more moderate ranges, but probably won't perform well if impact velocities are below 2000 fps.

Here is an extensive bullet test done by Gary Sciuchetti and posted in Handloader magazine in June of 1998. Number 193.

If anybody wants the complete article, let me know and I will post it here as soon as I can get it scanned.

Link to the chart above at stevespages.com:

http://stevespages.com/jpg/bestbullet.jpg

That's good. Never knew there was such a site.

Up in the San Juans,my old pal hit a spike bull at the base of the neck(as it quartered away) at about 500 yards with a 30/06-165 gr Nosler Partition started about 2950.

The bullet traveled the length of the neck and blew out the side of the bulls face.(If you have never shot one, an elk has a pretty tough neck,full of muscle and bone and not much else)

Next season, he hit another spike with the same rifle and load,through the hips as it ran through the quakies at about 40 yards(bum shot;do not try this at home ....it broke the hips,exited,and on the way cut the femoral artery.The elk skidded like a tractor and was DOA.

I don't know what this says about the theories of bullet expansion, but what it tells me is a guy might be better off not thinking so hard, just shoot a Partition, and not worry too much.

I have brung down at least two dozen elk and most of them were with the old '06 using 150 gr Remington corelocts. Never did have one let me down.

Thank you for posting that.

Ya'lls welcome.

Then you should keep using them.....I will stick with a Partition....Thanks.

Partitions are expensive