NEW 6.5mm Prototype: A Tale of Two Bullets

[KentuckyBuddha]

This is not a "flip-flop" or new trend for the 6.5 Grendel concept as a whole, it merely rounds out the available offerings. More bullet options is just neat-o!

(Or we could just go all "Donald Trump" on the issue and say, "Who cares what the 'whole rationale' is? We'll do what seems cool to us!" )

By the way, this is not a "mediocre BC" for its weight. It's about the highest BC one can squeeze out of a copper solid of that caliber and weight. You looked at the photo of it?

So what we really have is both high velocity AND high BC — a very cool combo. For the hunter, it reduces both drop and drift, minimizing aiming errors for quick kills.

It is an INCREDIBLE BC for the weight AND DIAMETER. For sure, as LRRP has said if you want the best BC for 75-80 grains you want a 5.56mm. For the weight class we are talking about with this pill, one could make a 6mm that would have a better BC but that in no way means that it is any sort of folly to have a 6.5 in that weight.

[BluntForceTrauma]

KB, I note that the BC will have to be recalculated now that the weight has dropped from 95 to 90. Still, the shape is the shape, and anyone can see it has an excellent form factor.

[Drillboss]

Hey, they can't have a monopoly on mythical creature names! They have no right to ruin the good name of the three-headed, snake-tailed, hound of hell!

Next bullet, all-brass, is named "Typhon," another creature in Greek mythology. . . .

Sounds good and nice work!

[stanc]

This is not a "flip-flop" or new trend for the 6.5 Grendel concept as a whole, it merely rounds out the available offerings. More bullet options is just neat-o!

(Or we could just go all "Donald Trump" on the issue and say, "Who cares what the 'whole rationale' is? We'll do what seems cool to us!" )

By the way, this is not a "mediocre BC" for its weight. It's about the highest BC one can squeeze out of a copper solid of that caliber and weight. You looked at the photo of it?

John, don't get me wrong. I think it is a beautiful bullet, very cool, and I wish you every success with it.

But, the BC (probably 0.300-something, at the new, 90-gr weight) is definitely mediocre relative to the original 123gr Scenar load.

[JASmith]

Chasing the logic of maximizing BC would take us to rather heavy bullets with unistering trajectories.

It is pretty clear, however, that the Cerberus will be the flattest shooting Grendel bullet out to at least 400 yards.

If the hoped for low velocity expanshion threshold materializes, it would likely also be the most effective medium game harvester to boot.

I am hoping that the brass bullet will be close in weight and form factor. The machineability of some brass alloys gives the possibility of sn inexpensive blasting bullet with a near-match in trajectory.

[sneaky one]

BFT, how about Typhoon ?

Stan, think inside of 350 yds. deer hunts. Look at the deer I harvested with a 77 grn. Gmx this season. This 90, will do anything a 120 cup core pill will do to 350y. If the expansion is correct.

Plus leadfree, and stable in flight. Can use this design to draw from for future pill- just tweak it. It's awesome.


JAS, if the expansion is not optimal,- I will be getting some with tips not installed- I can try some with deeper drilled -tapered- cavities, to see if it helps, I can tweak them here.

If an issue pops up- the design can be adjusted in a heartbeat.

Experiment 1 is being produced. We just need it in hand to start load workups.

I have a ton of data on Mono pills , after tweaking them for 6 years. Wt's. from 70-105. Six powders were used- 1 more may be added soon.

This will be fun.

[BluntForceTrauma]

Ballistic Coefficient (BC) issue got me curious. I recalculated the BC using the Bullet Drag Calculator website that I’ve mentioned a couple times. This website is not quackery or flakey; it’s real-deal physics.

I made two screen grabs, one of my inputs so you can independently verify them, and the second of the results. You can see the various BCs at various Mach numbers. (Mach 1 is essentially the speed of sound, or 1116 fps.)

So Mach 2.5 is 2.5 x 1116 = 2790 fps. So, if we can launch this bullet at 2790 fps we can get the BC listed at Mach 2.5, etc.

[KentuckyBuddha]

Fower Five Zero is enough to make me smile hard enough that my face hurts a little.

That will be far more than adequate for anything I ever plan to shoot (assuming I do my part with placement, and I certainly plan to do).

[cory]

Ballistic Coefficient (BC) issue got me curious. I recalculated the BC using the Bullet Drag Calculator website that I’ve mentioned a couple times. This website is not quackery or flakey; it’s real-deal physics.

I made two screen grabs, one of my inputs so you can independently verify them, and the second of the results. You can see the various BCs at various Mach numbers. (Mach 1 is essentially the speed of sound, or 1116 fps.)

So Mach 2.5 is 2.5 x 1116 = 2790 fps. So, if we can launch this bullet at 2790 fps we can get the BC listed at Mach 2.5, etc.

P.S. OK, I see the attachments suck. I don't know why they don't upload at original size. Will figure it out tomorrow. Hint: Mach 2.5 BC is 0.450. Yes, my fellow barbarians, point-four-five-zero.

We need to remember that theoretical physics rarely transfer perfectly to the real world. Looking at bullets in the 123gr and the 127gr LRX, I can just about guarantee that we're not going to hit a BC of 0.450. Now that's not a knock on the bullet, just trying to help keep expectations reasonable.

A BC of 0.400 will be exceptional for this class of bullet. I'd advise not speculating to much on the BC until real world drops can be collected out to 1000 yards in 100 yard increments.

[BluntForceTrauma]

Hey, Cory, THIS time I'm listening to you! And, of course, I agree that "in theory there's no difference between theory and practice, but, in practice, there is." (What movie was that, again?)

So, while I agree we can't hang our hat on these — VERY good — BC numbers without shooting them, at least the trend is VERY encouraging.

My amazing bullet guy says they're due to ship today.

[stanc]

Ballistic Coefficient (BC) issue got me curious. I recalculated the BC using the Bullet Drag Calculator website

Wait, what? At 95gr, it has a 0.410 BC, but at 5 grains lighter the BC is 0.450???

[BluntForceTrauma]

Stan, it all depends on the inputs. I think the 95 at 0.410 was an earlier design. Either that, or I quoted it super conservatively. But as I said, you can examine my inputs and results as posted. It's all there on the table; you can go to the website and punch in numbers to verify for yourself.

For the final 90-grain design, my dimensions as inputted into the program are accurate. If his program is wrong, that's another question. But that's like saying the well-respected JBM Ballistics Calculator is schlock.

So I'm cautiously optimistic.

[BluntForceTrauma]

Wound Theory of 90 Cerberus Mechanism

The best bullet shape for maximizing a wound channel is a wadcutter, a flat-faced, sharp-edged cylinder. And the bigger, the faster, the better. But we are constrained by the caliber of any given cartridge, and so we try to make the best of it, and make bullets outperform their size.

Problem is, wadcutters are not very aerodynamic. So we basically put a “nose cone” on them, which then removes their ability to smack the target and bore out a chunk of meat and instead provides a pointed nose that slides through tissue producing “ice-pick” wounds.

Ice-pick wounds from pointed bullets can be avoided if the bullet either fragments or yaws and then tumbles upon impact. The problem with fragmentation is that it is velocity-dependent; without enough velocity to cause fragmentation you’re back to an ice-pick wound. The problem with tumbling bullets is that they can veer off path and miss the vital target zone at which one was aiming.

Flat-nosed bullets — commonly used by African hunters on dangerous game — or wadcutters are very good at boring straight through the target as aimed.

What is it about wadcutters that works? Rocket scientist and ballistician Duncan MacPherson wrote the book on it (Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma). Using physics he explained that a bullet wound has both a distance and a time component. Imagine a block of ballistic gelatin. As a bullet impacts it and starts to bore its way through, the gelatin has to move out of the way of the bullet by at least the distance of the diameter of the bullet, to let the bullet pass through. This is the distance component. Though it happens in milliseconds, it takes a certain amount of time for the gelatin to travel from the small tip of the bullet and up and over the curved nose portion, or ogive, to the full diameter of the bullet. This is the time component.

In the case of a 6.5mm bullet with a nose one inch long, the gelatin moves 3.25mm outward radially from the bullet tip in the time it takes the bullet to travel one inch. This one inch of travel is actually slow enough to allow the bullet to slide through with minimal destruction. The shock coming from the impact of the nose of this bullet (which creates the temporary cavity) is like knifing your hand, fingers first, into a barrel of water.

Next consider a 6.5mm roundnose bullet, or, better yet, consider a 6.5mm bullet that mushrooms to 1.5x diameter, which effectively gives one a 9.75mm roundnose, a bit bigger than a roundnose 9mm pistol bullet. Again, after impact and once the mushroom is fully formed, the gelatin must move outward radially from the face of the mushroom, up and over its semi-circular surface, to its full diameter. Effectiveness is increased because the distance is increased and the time is decreased. The shock coming from the impact of this bullet is like making a fist and punching the surface of water, and produces a correspondingly bigger temporary cavity, not to mention a bigger permanent crush wound channel.

Next consider a 6.5mm wadcutter, a cylinder with a sharp-edged face and with zero curved bullet nose. The gelatin still must move 3.25mm outward radially from the bullet but it has ZERO time in which to do it! This means the smack of the impact crushes the gelatin in its path, destroying it. The shockwave coming from the impact of this bullet is like slapping water with your open palm, and produces, relatively, the biggest temporary cavity.

Anyway, this is book-length stuff. For those whose eyes are not yet glazed over, the 90 Cerberus bullet is designed to combine wadcutter wounding effects with an aerodynamic “nose cone” for good ballistic coefficient. At high-velocity impact the aluminum tip — with its large-diameter stem — is pushed backwards to crush the thin walls of its nose cavity, blowing them outward and leaving the wadcutter copper body. At lower velocities the nose cavity peels back to present a traditional mushroom. So, this bullet provides either best, or at worst, better wounding. Make sense?

This, at any rate, is the theory. And as Cory says, it has got to be proven out by testing. This will get underway after delivery, which I am guessing will arrive sometime next week.

[sneaky one]

If this closely resembles the Gmx's performance, that I have used for tests. , and hunts- it will be fine. Smack em hard !

[customcutter]

I was thinking .380-.390 range for BC, anything above that is just gravy!