Rifle bullet velocity and expansion/non expansion

I think Hornady actually lists the velocity thresholds it's bullets are designed to perform in, or did at one time, in their manual. Most traditional cup-and-core JSPs from any manufacture will show useful expansion down to about 1800 fps and stay together up to about 2800 fps. Of course nose profile matters. A round nose soft point such as a 150 gr offering for a .30-30 will probably expand to a lower velocity than a similar pointed or spitzer offering, but of course the pointed offering is likely to have a higher BC and arrive downrange with more velocity.

Right around 2000 fps is a good minimal velocity threshold, IMO, because it leaves enough velocity for even most premium bullets to expand and because that is right around the velocity that your rifle stops killing like a rifle. So-called "hydrostatic shock" forces need about 2000 fps depending on the density of the tissue, to cause damage through cavitation. Once your projectile dips under 2000 fps, it rapidly becomes progressively unlikely that you will see damage in the temporary stretch cavity and more likely that your bullet is going to behave more like a small caliber handgun bullet damaging tissue it displaces only directly in the permanent wound cavity. So when I am deciding what I am going to call the maximum effective range of a particular load in the field I input the most accurate data I have available into an external ballistics calculator and determine where my load hits 2000 fps. My maximum effective range with that load will be primarily dictated by my abilities with that rifle and load but will not exceed the range at which the load drops below 2000 fps. Not many sporter-weight rifles and loads will get you much past a quarter mile, even from a 7mm Rem Mag. That's on a game animal or any situation I feel morally obligated to kill as humanely as possible. Obviously determining effective range of a rifle and load for use in combat against people actively trying to kill you would involve different circumstances.

^ good post

Most manufacturers DO list the recommended velocity windows.
You do also need to remember the opposite side.of the spectrum as well. Very close shots with even "regular" cartridges, can have bullets impacting at over their recommend velocities. If very short range hits are the norm that needs to be taken into consideration when choosing a cartridge or bullet.

For a "do all" the bonded bullets, i guess because of how they are made, have a larger velocity window than mono, or cupncores. Most of what ive read say they will expand properly down to 1800 and sometimes lower, but since they are bonded ill still hold together on short range hits....tho obviously not as well as a mono would.

Thus were I hunting an area where I had little, or no idea of how far id be shooting, id probably chose a med/heavy bonded, driven from any modern (or modern loading) cartridge.

For reference, and this is just my personal opinion.
I like heavy cupncores launched at 2700-3k for most applications.
Med/heavy bondeds launched anywhere above 2700
And last but not least (expensive) I do like the light/med monos launched over 3k....and realy as fast as they will go....

I have the least experience with monos of the lot, i never really got good accuracy...which was probably my fault.

Nosler also publishes some recomended minimums for there ballistic tips. When in doubt call the manufacturer and they will tell you.

It depends on the individual bullet, but 2800 fps down to about 1800 fps is a good guide. I wouldn't argue with the 2000 fps minimum suggestion above, 1800 is sorta the minimum and 2000 would probably be better. The harder premium bullets will hold together above 2800 fps, especially the copper bullets. While copper stays together at speeds well over 3000 fps, MOST of them expand very little below 2000 fps and 2200 fps seems to be a better number. That holds true with bullets 30 caliber and smaller. The larger caliber bullets seem to expand adequately at slower speeds. And some bullets designed for 30-30 speeds open up much slower, but will expand too much at 2800.

I've come to the conclusion that impact speed and bullet construction are much better indicators of bullet performance on game than energy numbers, bullet weight, or caliber. If you use a bullet tough enough to give adequate penetration and if it impacts within the velocity range it is designed for it'll kill stuff. If it impacts faster, or slower than it is designed for performance may be poor. Most modern cartridges will maintain 1800-2000 fps farther than most guys can shoot. The bigger problem is usually too much speed at close range.

Of course this assumes modern bottleneck cartridges. If using old school large caliber rifles shooting heavy bullets the rules are different. They don't depend on speed for bullet expansion.

LoonWulf said:

For a "do all" the bonded bullets, i guess because of how they are made, have a larger velocity window than mono, or cupncores. Most of what ive read say they will expand properly down to 1800 and sometimes lower, but since they are bonded ill still hold together on short range hits....tho obviously not as well as a mono would.

Click to expand...

+1

Hornady actually recommends the 130gr Interbond for 6.8 SPCs with adequate mag length because, due to the way bonded bullets are manufactured, they expand better and more reliably at lower velocities than most C&C bullets.

LoonWulf said:

^ good post

Most manufacturers DO list the recommended velocity windows.
You do also need to remember the opposite side.of the spectrum as well. Very close shots with even "regular" cartridges, can have bullets impacting at over their recommend velocities. If very short range hits are the norm that needs to be taken into consideration when choosing a cartridge or bullet.

For a "do all" the bonded bullets, i guess because of how they are made, have a larger velocity window than mono, or cupncores. Most of what ive read say they will expand properly down to 1800 and sometimes lower, but since they are bonded ill still hold together on short range hits....tho obviously not as well as a mono would.

Thus were I hunting an area where I had little, or no idea of how far id be shooting, id probably chose a med/heavy bonded, driven from any modern (or modern loading) cartridge.

For reference, and this is just my personal opinion.
I like heavy cupncores launched at 2700-3k for most applications.
Med/heavy bondeds launched anywhere above 2700
And last but not least (expensive) I do like the light/med monos launched over 3k....and realy as fast as they will go....

I have the least experience with monos of the lot, i never really got good accuracy...which was probably my fault.

Click to expand...

Good post. To the OP, for many people over expansion can be a problem.
For instance, a couple years ago I shot a deer with a 243 100 grain coreloct at 25 yards. That bullet was moving way too fast at impact and it acted more like a varmint ballistic tip, it exploded and I have very little penetration. That same round outside of 50 yards has slowed enough that it gets great penetration. If getting shots under 50 yards is a likely scenario, consider what Loon said and get bonded bullets. I like the accubond but several companies make good ones.

Several years ago, there was a fellow who tested the penetration of various 30 caliber bullets at different impact speeds. It was quite a project apparently.

Here is average penetration in inches vs. impact speed in FPS for three common cup and core bullets.

With exceptions, they tend not to open below about 2100 FPS and just pencil on through for very long distances. Above 2800 FPS, they tend to fail, and penetration drops off sharply.

IIRC, it was the Hornady Spire Point that reliably opened at 1800 FPS.

Many newer bullets open at 1800 FPS, and some hang together until Warp 10.5.

I shoot copper exclusively, and I plan to trade in my 308 for a 270 win or 300 wsm next year. The 270 win would give me 2400 fps to 350, and the 300 wsm would give me 2400 to 400. The 308 doesn't launch copper bullets fast enough for my tastes, unless I want to go down to 110-130 grain bullets.

Dr.Rob said:

30 cal sierra game kings (spitzer boat tail soft point) are said to be good down to 1600 fps. It's a very good long range bullet.

Click to expand...

No offense, but said by whom? Barnes says their ttsx is good down to 1800 fps, but that seems... optimistic... Most who use them seem to say 2200-2400 fps at a minimum (assuming you don't hit bone).