Terminal velocity


Well-Known Member
Jun 12, 2001
Palmer, Alaska
At what speed do you believe one needs a bonded core, partitian type or X bullet for a, prepare for the worst double shoulder shot on moose or elk size animals? My best guess would be maybe 2500fps or faster.

A shot on a moose I made at 640 yds with a 400gn Swift A-frame (2650fps) 416wby broke one shoulder and exited, indicating not enough expansion for the amount of velocity left.

The other notable shot was at 200yds, same bullet, through the neck and scapula and stopped under the skin with .750" min diam.
The shear shock must have severed his cord because the spine was missed by an inch and half. He hit the ground sideways and never twitched once.

I don't think in fps for carrying a premium bullet in the chamber, I think more in distance and cover. If there is a fair chance that I'll encounter the game I'm after in a manner such that I can't pick an easy kill double lung or brain shot AND I'm out to get that game animal with no option of a second attempt I'll carry Partitions loaded. Once I'm in the clear and can more easily prepare for the premier shot I'll reload with the standard fare bullets and loads.
The rifles I use don't particularly like Partitions (accuracy) and I don't care for the low BC so I don't use them for long range. I DO use the partitions for dangerous game where I won't be shooting long range anyway.

I do have a velocity limit for Ballistic Tips, 3000 fps but it's more where I place the shot than switching bullets. Over 3000 fps I'm going for double lung or brain or just pass on the shot. I use the BTs in my 300 Win Mag for deer and I'm hardly ever concerned with not having a second chance on deer (they've nearly been lowered to varmint status here, this year we have UNLIMITED antlerless archery tags and the season is 4 1/2 months long).

On the pass through shot on the moose... I'm not one that subscribes to the "bullet must stop in the animal" theory. There's nothing wrong with that line of thinking and in my mind it all relates to confidence and that's ultimately what's important.
Here's how I imagine that last little bit of the bullets' travel in the critter happens. Once the bullet is in the critter and passes through the offside it encounters the inner surface of the skin. This skin initally begins to act like a catchers mitt as the connective tissue holding the skin to the underlying muscle is compromised. The skin bulges outward slowing the bullet and absorbing some amount of the energy and if it can hold together it 'catches' the bullet or it fails and the bullet passes through. On the off side of the critter there is no supporting solid structure to hold the skin in place and make the passage of the bullet easy as on the near side of the critter. Depending on the looseness of the skin and the diameter of the bullet varying amounts of energy are taken up by the skin, all the mortal damage has already been accomplished and it's not important how much or how little energy is absorbed by the off side hide. This is how I imaging the sequence takes place as I've never seen high-speed video of a bullet exiting a body.

Also, I don't imagine the dead moose cared whether or not the bullet stopped under the skin on the off side.

Let's see what other folks subscribe to in the pass through vs non pass through theories.

Good Hunting
Dave, I understand and agree completely.
I was just trying to point out that at 640 yds a average bullet would have done just fine because expansion was not as violent.

I too carry the premium bullets in the timber etc. when a grizz may pop out. The reason I use the X bullet longrange is the BC and the group size of .7 moa max.

My sons .308win won't shoot the X bullet under 1.7 moa so he just uses it in the timber and switches to the 165gn Gameking SPBT at LR that goes under .5 moa with factory loads at 2600fps out of a 20" tube.

His first moose was a double lung shot at 200yds and a complete pass through with the 165gn Gameking, It measured 59.5" and the body was enormous.

A pass through shot leaves one more blood trail and twice I've needed that. Both times the animal was less than 80yds away, but one bush can hide an animal for a long time.

Just another example of bullet construction, my 416wby at 10 feet will push a 400gn Barnes X 16-20" in silty sand, but the 400gn A-frame only 4-6" and it is literaly smoking for 10 seconds afterward. Both are .800-.900" in dia. and weigh 85% or more. The A-frame just expands faster at 2650fps or any speed.
When you are talking penetration frontal diameter becomes a major consideration - and velocity is what creates mushrooming in most bullet designs.

If you shoot a 180 grain A-Frame bullet (or most other bullet designs) horizontally into a water tank at .308 Win. velocities and at .300 Win. mag velocities the .308 Win. will always penetrate farther since it does not have as much impact velocity so it does not mushroom as large and therefore sheads energy slower.

I have seen the test tank at Swift and they told me that is how it works.

That might explain your results?
Brent and Ian,

What you say is true, concerning mushrooms and impact speed. What kills is the wound channel, both the width and depth. Penetration velocity (not impact velocity) is very important to the width of the wound channel. A large diameter projectile or mushroomed bullet may not cause as wide a wound channel as a projectile with a lesser cross section but penetrating much faster. This is the wave effect and is especially noticeable in projectiles that impact above 3300 fps, present moderate cross sections, and maintain their mass and velocity at a much higher level.

Most conventional mushrooms take from 17-23% of the total available energy upon impact just to form the expanded shape (mushroom). This is energy that is not available to perform the work of penetration. There are other ways to present an enlarged cross section and do it using only 3-5% of the total energy at impact.
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