UNDERSTANDING TERMINAL BULLET PERFORMANCE

With deer season raging in some places and starting tomorrow in others, there will be a lot of discussions in hunting camps about bullet performance. Maybe this will clarify some arguments and possibly confuse some others.

With the exception of solids and a few odd bullets like the Berger VLD Hunting bullet (More on it later.), all bullets begin to expand as soon as they impact something. Some believe that tough bullets are slower to expand when in fact the opposite is true. The harder an expanding bullet is, the faster it reaches its final shape. Why? Because the harder it is, the more velocity it needs to open and the deeper it travels, the slower it goes. A tough bullet’s best chance to expand is when it is traveling the fastest.

Softer, lead core bullets continue to deform as they slow down because of the soft lead core. Some cores are lead alloys and harder so they stop shape shifting sooner.

Regardless, every bullet has three wounding tools; crush cavity, wound cavity and stretch cavity. (See Diagram 1) The crush cavity is equal in diameter to the expanded size of the bullet and the depth the bullet penetrates. The wound cavity is the tissue around the crush cavity that is destroyed by the expansion and passing of the bullet. Bullets that shed material create wider wound cavities. The wound cavity is why you can look in a deer’s lungs and see a hole larger in diameter than that of the expanded bullet.

DIAGRAM 1

Finally, there is the stretch cavity. This is the void created inside an animal due to the splash of the bullet. It is generally a product of how fast a bullet reaches its ultimate shape and impact velocity. You cannot see the stretch cavity inside a dead animal but it can have impact on incapacitation depending on where it is.

With adequate penetration, the only differential between bullets is how big the wound cavity is. Diagram 2 shows how lead core bullets like Ballistic Tips, CoreLokts, Accubonds and Partitions generally create wider wound cavities and it also shows how mono metal bullets like Triple Shocks, E-Tips and GMX bullets penetrate deeper.

Diagram 2

If your bullet penetrates deep enough and you place the shot correctly – this will depend on the animal shot, its attitude toward you and where you hit it – it will not matter if it is a mono metal or a lead core bullet. IF, and this is a big IF the animal is not so far away that impact velocity has dropped below what is needed for your bullet to expand and IF the animal is not so close that impact velocity is so high the bullet comes apart.

For long range shots you should strive for an impact velocity of at least 2000 fps and for close shots, don’t worry unless your muzzle velocity is over 3000 fps. If it is, you might want a mono metal or bonded bullet to avoid bullet blow up. But even then with deer, which are not to hard to kill, it probably will not matter, especially on broadside chest shots.

The anomaly – the Berger VLD Hunting bullet – does not start expanding upon impact. Due to its high BC and secant ogive – how sharp this bullet is – it will penetrate about two to four inches inside an animal passing through even bone before it begins to deform. When it does deform it sort of implodes on itself and acts like a bomb. If this occurs inside the vitals of the deer, incapacitation is often very rapid.

Obviously, this is an extreme over simplification of terminal bullet performance. I’ve tested hundreds of bullets in various mediums and they all create different wounding patterns. However, trends and similarities exist. So much so that I challenge anyone to look at the insides of a dead deer and tell me if it was shot with a CoreLokt or a Nosler Partition. If you cannot make that determination with 100 % certainty, it does not matter which bullet was used.

Just the same, I’ll bet you cannot differentiate between a deer shot with the same type bullet from a .243 Winchester, .25-06 Remington or a 7mm-08. I’ll go as far as extending the same bet to anyone that can look inside a deer and tell me if it was shot with a .308 Winchester or a .30-06. But, that’s an argument for after deer season.

Advertisements

About gunwriter

Born and raised in the West Virginia hills, Richard literally grew up in the woods. He has chased coon hounds until daylight, waited out whitetails perched high in an oak, canoed the New River and hunted from the Montana Mountains to the Green Hills of Africa. During service in the Army and later as a municipal police officer and Special Agent with the railroad police, Richard obtained numerous certifications in small arms instruction. He has trained military personnel, law enforcement officers and civilians in the application of firearms for defensive, competitive and recreational use. Richard won the West Virginia Governor’s Twenty Award for law enforcement, the West Virginia National Guard State Pistol Competition and earned his Distinguished Medal with pistol. Badge turned in, Richard is now a contributing editor for several magazines. He was the compiling author of the book, Rifle Bullets for the Hunter and conceptualized and contributed to Selecting and Ordering a Custom Hunting Rifle. Richard also contributed a chapter to the John Velke book, The True Story of the Baldwin-Felts Detective Agency. Richard has patents on a riflescope reticle and a revolutionary bullet testing media. A hillbilly at heart, Richard lives on Shadowland - his shooting range in West Virginia - with the most understanding wife in the world, their three kids and a very protective ridgeback hound.
This entry was posted in THIS & THAT and tagged , , , , , . Bookmark the permalink.

3 Responses to UNDERSTANDING TERMINAL BULLET PERFORMANCE

  1. Mark McDowell says:

    The one shot with the .308 is the one in front of my stand. That’s the only difference…
    Be safe,

    Mark McDowell

  2. Mike Wodjenski says:

    You also cannot tell the difference between a .375, 30-06, or .264 if you hit a twig on the way to the animal! Aaargh!

  3. Doc B says:

    “…this will depend on … its attitude toward you…”

    I think it was pretty pissed off, at least for a few seconds. Overall, the critter had a bad attitude. So I shot it.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s