DocKGR When is a rifle bullet too slow to act like a rifle bullet?

[nincomp]

Doctor Roberts, - (oops, sorry about misspelling your screen name...but dislexics are teople poo!)
Thank you for your work and sharing your knowledge in articles like: “Basic Wound Ballistic Terminal Performance Facts.” Background: the article explains that one of the major differences between “pistol-like wounds” and “rifle-like wounds” is the additional damage caused by the larger temporary cavity from the rifle’s more rapidly traveling bullet. You stated: “tissue that was stretched by the temporary cavity may be injured and is analogous to an area of blunt trauma surrounding the permanent crush cavity.” I noticed an August 1999 “Tactical Briefs” article, that explains that the size and location of the temp cavity can explain the DRT effect (dead right there): where the person or animal collapses immediately and doesn’t move before expiring.(reference below).

My question comes from the vigorous, err, “discussions” on various websites about the “effective range” of various rifle cartridges and their bullets. The cartridges include .223, 6.5mm, 6.8mm, 30blk, 7.62x39, and, for old farts like me, .30 carbine and 30-30. There are claims that some newer rifle bullets reliably expand at lower velocities. Your sticky on the M1 Carbine mentioned the Speer 110 gr .30 carbine gold dot. In addition, I have seen reports about a .30 cal monolithic bullet that is said to expand from about 2400 fps down to 1300 fps. - No high speed photos of the gel tests, however.

At 2300 or 2400 fps, I would think that the bullet would cause “rifle-like” wounds. But what about farther downrange when it has slowed to 1600 fps or to 1300 fps? Has the effectiveness dropped to a pistol-like “crush area only” wound?
Note to flamers: I am not saying that the slower bullets can't be deadly. But slower bullets would cause less damage and would lack the attention-getting oomph that comes from a cantaloupe-or-larger-sized temporary cavity suddenly opening in your chest or thigh.

Based on your experience, at roughly what velocity do the bullets lose rifle-like effects. Is this velocity lower for expanded bullets?

Thanks.


Reference:“Blunt Trauma Concussion of Spinal Cord as Mechanism of Instantaneous Collapse produced by Centerfire Rifle Bullet Wounds to the Torso” : www.firearmstactical.com/briefs28.htm

[Spooky130]

Not an expert by any means but watching the development of the .300 AAC has been interesting. It seemed initially the round would be hampered by availability of bullets constructed to perform optimally at the velocities generated. Of interest was the Barnes line - long, sleek homogenous copper bullets built for hunting seemed like they would work but were really not optimal because they were built to operate at higher velocities found in the .308, .30-06, .300WM, etc. Luckily the corporate entity behind the .300 AAC were able to have Barnes build them a bullet to work at lower velocities found in the .300 AAC. Bottom line - study your bullets you intend to use and determine if they will work in your velocity ranges.

[bzdog]

You make a good point about how different bullets are designed for specific velocity ranges, but I think the OP was asking more about how fast the bullet needs to travel to switch from pistol-like wounding characteristics to rifle-like.

I'm interested as well because The 300 Blackout rounds seem to it between pistol velocites and 5.56 velocities.

-john

[nincomp]

Spooky, you are right, but as bzdog noted, I am more interested in the low end of rifle-like velocities.

To provide more context for my question: I have been following intermediate cartridges like the 6.8 SPC since Doctor Roberts first mentioned it on the Tactical Forums website. Now there are more intermediates and yes, bullet companies including Barnes, are tailoring rifle bullets for lower velocity ranges.

Now that more rifle bullets can open up or "upset" at lower velocities, when do they begin to act like pistol bullets? Again, there is no doubt that most intermediate rifle cartridges work well at shorter distances (with the right bullets). Most of the arguments that I see are about effectiveness at longer ranges: 300m, 400m, and in the case of the 6.5 Grendel, considerably longer ranges.

Of course, precise shots that hit the CNS or heart are deadly at long range. The problem is that those precise hits become less and less likely with real world conditions like wind, unknown distances, no spotter shots to zero-in, and less than ideal shooting positions.

On a personal note, I am especially interested in the intermediate cartridges since a serious spine injury has prevented me from shooting for several years. One day, I might be able to shoot an intermediate cartridge, but firing a 300WM would likely result in an ambulance ride for me.

[C-grunt]

I have read before that the threshold for serious wounds outside of bullet tack to be somewhere around 2000 FPS.

Edit: however DocGKR has said that bullet profile has an effect in it to. As in a .223 that doesn't yaw will have a much smaller TC than one that does.

[Spooky130]

You make a good point about how different bullets are designed for specific velocity ranges, but I think the OP was asking more about how fast the bullet needs to travel to switch from pistol-like wounding characteristics to rifle-like.

I'm interested as well because The 300 Blackout rounds seem to it between pistol velocites and 5.56 velocities.

-john

Gents,

I'll try to find the posts from the folks at Barnes building their new 110 grain TAC-X bullet for the .300AAC. They list a lower end velocity number where that specifically designed bullet stops expanding.

[bzdog]

Gents,

I'll try to find the posts from the folks at Barnes building their new 110 grain TAC-X bullet for the .300AAC. They list a lower end velocity number where that specifically designed bullet stops expanding.

http://www.300blktalk.com/forum/view...barnes#p730016

This may not be the exact bullet, but it suggests the 110gr VOR-TX 300BLK should expand down to around 1300-1500fps and actual performance is around 2350fps.

http://www.barnesbullets.com/product...tx-ammunition/

So clearly, the bullet performs well below the velocity of that particular ammunition. And it looks like a really effective bullet and performs at the higher end of 300 BLK velocities due to the light weight (for a 300 BLK).

That said, it isn't clear if we get the temporary wound channel effect at that velocity or not.

-john

[Jack-O]

From my investigations and research, Depending on diameter and construction, it appears that the crossover point is somewhere between ~1600 and ~1900. If I had to put a general number on it I'd say around 1700fps for a well designed .30 cal. Higher for a smaller and lower for a larger bullet.

it's that crossover point that makes the magnum pistol round interesting as they are breaching that threshold with some loads.

[kenndapp]

From my investigations and research, Depending on diameter and construction, it appears that the crossover point is somewhere between ~1600 and ~1900. If I had to put a general number on it I'd say around 1700fps for a well designed .30 cal. Higher for a smaller and lower for a larger bullet.

it's that crossover point that makes the magnum pistol round interesting as they are breaching that threshold with some loads.

is this to say that a 300blk leaving the barrel of an sbr (7.5-10") around 2000 fps would most likely only provide your target with a .30 caliber (with expansion) crush cavity? at that point wouldn't a pistol caliber (larger in caliber) provide better terminal ballistics on your target? i was under the impression that 300blk ( or other slow riffle caliber fired from an sbr) would provide some enhanced terminal effect over a pistol caliber? is my logic off?

[Jack-O]

my understanding is that projectile design and performance can bridge the gap somewhat.