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Zhukov
09-30-09, 21:54
Of all the manufacturers I know, only Hornady lists the proper velocity range for their handgun ammunition to perform properly. For rifles, even less data is available.

I assume that for expanding bullets, the drop-off in performance bears a near inverse linear relationship to velocity, while fragmenting bullets will show more of a step function.

Besides the much-publicized data for M193 generated by Fackler many years ago, is there a list of the velocity threshold below which bullets of a certain construction no longer function properly and could be considered FMJ?

Hornady shows their GMX performing as follows for 3400, 2700, and 2000fps:

http://www.chuckhawks.com/hornady_GMX_150.png

bernieb90
10-01-09, 02:21
Of all the manufacturers I know, only Hornady lists the proper velocity range for their handgun ammunition to perform properly. For rifles, even less data is available.

I assume that for expanding bullets, the drop-off in performance bears a near inverse linear relationship to velocity, while fragmenting bullets will show more of a step function.

Besides the much-publicized data for M193 generated by Fackler many years ago, is there a list of the velocity threshold below which bullets of a certain construction no longer function properly and could be considered FMJ?

Hornady shows their GMX performing as follows for 3400, 2700, and 2000fps:

http://www.chuckhawks.com/hornady_GMX_150.png


I have seen very similar pictures for the Swift Scirocco, on their website. I have also seen some gun magazines perform high/low velocity tests on a number of hunting bullets. The problem is that we don't know what media the factory used to perform their tests. Water, or worse yet clay will tend to exagerate expansion at low velocities.

I performed the same test on my own bullets that I machined fired into water.

http://i82.photobucket.com/albums/j275/bernieb90/DSC_0385.jpg
Unfired, 2945 fps, 2190 fps

The results in tissue may or may not be the same.

The other issue is that stagnation pressure is a function of V^2 so we may see dramatic changes with small velocity increases especially above 3000fps where fluid pressures exceed 60,000 psi on the tip of the bullet. Going from 3000fps to 3300fps results in nearly 13,000psi increase in fluid pressure.

I also think that many bullet companies are reluctant to publish pictures or data due to the fact that most recovered conventional bullets don't look very good in pictures even at modest velocities. This is why we often see this info for bonded bullets (typically form classic mushroom) or monolithic bullets, but not conventional bullets.

I think it is safe to assume expansion of most convetional, unbonded SP, HP, and tipped rifle bullets down to 1800fps. Bonded bullets, and monolithic bullets down to 2000fps.

Zhukov
10-01-09, 10:43
bernieb90: Interesting point about the stagnation pressure. I wasn't aware of the relationship between v^2 and the pressure.

My personal experience has been with the 150gr Nosler Ballistic Tip in 7mm Rem Mag. I believe I have only ever recovered one bullet, and it was fragmented pretty well - about what I would expect from a bullet of this type. On the relatively small deer here in Central TX, the results are usually devastating (I load them to about 3000fps - certainly not pushing them).

On the non-hunting front, the reason I asked this question is because I get a lot of questions about how far such-and-such a bullet will be effective. Hopefully I'll get some good data to add to my FAQs...

DocGKR
10-01-09, 12:55
For some types of projectiles, there are other factors at play than simple linear velocity. For example, let's look at a hypothetical JSP projectile launched from a 20" 1/10 twist barrel with a MV of 2900 f/s; the projectile hits a target at 300 yds with an impact velocity of 2100 fps and expands normally. Yet when that same projectile is launched from say an 8" 1/10 twist barrel with a MV of 2100 fps and hits a target 3 yds away, the projectile fails to expand. Why? The impact velocities are the same, so why did the projectile launched from the short barrel fail to upset? A major variance is the difference in rotational velocity. While the impact velocities for the two shots are the same, the shot from the longer barrel has a much higher retained rotational velocity at 300 yds--in this case say 35% higher than even the initial rotational velocity of the SBR, as rotational velocity decays at a much slower rate than linear velocity.

Zhukov
10-01-09, 13:42
That's very interesting - are there any scientific papers published about this effect, or is this from personal observation?

DocGKR
10-01-09, 14:24
At present, there are no open source, public papers on this topic.

DBR
10-02-09, 15:19
Not withstanding the rotational variable Barnes Bullets will tell you the expansion window for any of their bullets if you call them. At least they have been forthcoming when I have asked.

Add Nosler to the list of bullet mfgs who will give expansion window info over the phone. I called them re the Nosler Partition bullet.

Zhukov
10-03-09, 08:39
Not withstanding the rotational variable Barnes Bullets will tell you the expansion window for any of their bullets if you call them. At least they have been forthcoming when I have asked.

It's strange that they don't publish that data when it's not secret in the first place.

DBR
10-04-09, 18:01
Manufacturers do tweak designs over time. Maybe they don't want the hassle of trying to keep the info up to date. Or, maybe they don't want published info available for competitor comparisons.