THIS Is the Dedicated 65G Bullet I Want, Part 2

[BluntForceTrauma]

Cory, I want a 100 or 105 grain military bullet, whichever tests out better. I should explain myself better: I want the 90 gr with a 7mm polymer tip for hunting. But for a military bullet I want about 90 grains copper PLUS a 7mm hardened steel tip along with its inner stem. Since steel weighs more than plastic, the final weight is gonna be higher; goal would be 100 or 105 for assault rifles. I want that extra BC.

For linked MG ammo, I'd increase the pressure, assuming the bolt mechanism can handle pressure better than an AR, and load a 123 for increased smack.

[stanc]

Cory, I want a 100 or 105 grain military bullet...for assault rifles. I want that extra BC.

For linked MG ammo, I'd increase the pressure, assuming the bolt mechanism can handle pressure better than an AR, and load a 123 for increased smack.

A couple of issues:

1. 123gr may not be feasible with a lead-free design.
2. Standard practice is to have the same load for rifles and machine guns.
3. Why set arbitrary weights? Wouldn't it be better to let testing determine optimum bullet weight?

[BluntForceTrauma]

1. Yeah, I was thinking lead core. Keep forgetting this asinine politically correct lead-free requirement.
2. Standard practice? Guess I don't play by the rules.
3. Quite right. Just reflects my thinking at the moment.

But let's not get too sidetracked in this thread. . . .

[stanc]

1. Yeah, I was thinking lead core. Keep forgetting this asinine politically correct lead-free requirement.

It may seem asinine, but steel-core ball ammo offers better hard target penetration than lead-core ball. And as I recall, you've expressed something like admiration for the practical nature of Russki small arms ammo developments. I would note that they've been using very low lead content in their bullets for well over half a century, and they've continually increased the amount of steel (with corresponding reduction in amount of lead) in 5.45mm bullets, as well as hardening the cores to enhance penetration. Going "green" has definite advantages for battlefield performance.

2. Standard practice? Guess I don't play by the rules.

Yeah. Neither do I. However, we also don't get to make the rules. If you want to gain acceptance by the military, it's probably a good idea to plan for what they actually do, rather than what we'd like them to do.

But let's not get too sidetracked in this thread. . . .

Roger. Wilco. Out.

[JASmith]

Minimum Opening Vellocity

A few posts earlier in this longish discussion, we saw comments about the forces bearing on the front of the bullet.

The dominant force on the bullets nose is hydrodynamic with a small overlay of essentially velocity independent target material strength. Target materials here are hide, muscle, and bone.

The variable force comes from the velocity term and simplifies to half of the velocity squared times the density. Since the term "1/2" is always present and the density is more or less the same, the remaining variable term is velocity squared.

That means that the hydrodynamic forces on the bullet's nose at 1600 fps are only about 60% (about half) of what they are at 2000 fps.

[Bigfoot]

That means that the hydrodynamic forces on the bullet's nose at 1600 fps are only about 60% (about half) of what they are at 2000 fps.

Thanks JASmith.

Copper or gilding bullets do not disintegrate, they sometimes lose their petals but always retain their core kinda like how a Partition does after the front end is blown off. Usually petal loss is by extreme velocity or by the bullet flipping around after the petals have opened and the petals shear because they're pushed forward (now you have a jagged edged, tumbling bullet) again. As I have said, petal shearing isn't necessarily a bad thing because at these high velocities a flat faced bullet will act like a hard-cast bullet. Again, read how GS Custom bullets work, they are made to shear the petals and penetrate deep relying on the core and the pressure wave off the flat meplat for tissue disruption.

By 'toughening the material' to change the opening velocity I meant changing the diameter of the cavity and nose insert to increase or decrease the thickness of the petals, not changing the composition.

I would suggest raising the min opening velocity to toughen it a bit but this is your baby.
EDIT: I suppose any changes might wait until a prototype is chronographed and sent downrange and we get an idea of it's BC. So....nevermind.

Easily changing the characteristics of a long nosed bullets terminal performance just by altering the nose cavity is one of the great features of having such a large nose junction.

[cory]

Cory, I want a 100 or 105 grain military bullet, whichever tests out better. I should explain myself better: I want the 90 gr with a 7mm polymer tip for hunting. But for a military bullet I want about 90 grains copper PLUS a 7mm hardened steel tip along with its inner stem. Since steel weighs more than plastic, the final weight is gonna be higher; goal would be 100 or 105 for assault rifles. I want that extra BC.

For linked MG ammo, I'd increase the pressure, assuming the bolt mechanism can handle pressure better than an AR, and load a 123 for increased smack.

From what I understand that steel tip of the M855A1 has caused nothing but problems. I've envisioned that tip within a polymer tip. It'd make the steel tip lighter and the entire bullet lighter, but I think it'd work much better.

A couple of issues:

1. 123gr may not be feasible with a lead-free design.
2. Standard practice is to have the same load for rifles and machine guns.
3. Why set arbitrary weights? Wouldn't it be better to let testing determine optimum bullet weight?

1. Why??? We currently have a 120gr TSX (Lead Free). If we are talking within the confines of the AR15 magwell, well I find it hard to believe we would stay with the AR15 (a platform designed for the .22 Remington) as it stands after adopting a new cartridge. Personally I think the best solution would be an AR15 modified.
2. As long as the 2 rounds are interchangeable in the platform, we'll still meet the intent of that SOP.
3. I agree, but we need to take our best guess to get a start.

[BluntForceTrauma]

That means that the hydrodynamic forces on the bullet's nose at 1600 fps are only about 60% (about half) of what they are at 2000 fps.

Thanks for the math, Joe, very good to have. If the hydrodynamic forces are half as the velocity decreases either from range or shorter barrels, that means one needs to "weaken" the tip as I've proposed to get expansion?

[stanc]

1. Why??? We currently have a 120gr TSX (Lead Free). If we are talking within the confines of the AR15 magwell, well I find it hard to believe we would stay with the AR15 (a platform designed for the .22 Remington) as it stands after adopting a new cartridge.
2. As long as the 2 rounds are interchangeable in the platform, we'll still meet the intent of that SOP.

1a. The 120gr TSX is all copper. A military bullet will be constructed with a jacket of gilding metal or mild steel, and a core entirely of steel, or part steel and part copper. Steel has lower density than copper, resulting in a bullet that is lighter for the same length. There are practical limits on bullet length-to-diameter ratio, and in the specific matter of 6.5 Grendel, there is the impact of projectile length on powder capacity that also should be considered. The Swedish 6.5x55 steel-core AP bullet weighs only 112 grains, and (I think) contains a lead sleeve around the core. This AP bullet (IMO) is about as long as practical for the Grendel cartridge case, and is probably close to the same weight as would be a projectile with M855A1-type steel/copper construction. Make it Nammo-type steel/steel core, and it'll weigh less than 112 grains.

If the Army should adopt a new rifle that does not have the cartridge OAL limitations of the M4/M16 family, they likely would opt for a bigger, longer, and quite possibly different caliber cartridge than 6.5 Grendel, in which event none of this discussion would matter.

2a. Negative. The primary intent of that SOP is to simplify manufacturing and logistics. Having a light bullet load for the rifle/carbine, and a heavy bullet load for the machine gun, would be contrary to that practice. Proposing such a light ball/heavy ball concept would almost certainly be inviting rejection.

[stanc]

Back on topic... I think this is what Variable is looking for. I'm not sure if it's what anyone else wants.

300 BLK 110gr Blacktip has an expansion threshold of 1300fps. The blue-tip 110gr .308" dia TSX bullet has an expansion velocity of nearly 500fps higher...

http://www.m4carbine.net/showthread....43#post1778743

https://www.youtube.com/watch?v=9mXa5AiT0r4

[Variable]

Sweet Heavens Yes! That's exactly what I'm wanting. I just want it grendelized with an appropriate Grendel BC.

Massage that bullet design for a 6.5 bore, and if it could squeak .40 or better it'd be nirvana!!!

[JASmith]

Thanks for the math, Joe, very good to have. If the hydrodynamic forces are half as the velocity decreases either from range or shorter barrels, that means one needs to "weaken" the tip as I've proposed to get expansion?

'Weakening' can be done through alloy adjustments, larger cavity with or without plug, scoring the nose, etc.

One hopes the professional bullet designer has a bigger bag of tricks in hand and that some of them result in affordable bullets.

That Vortex Stanc posted comes to mind.

[sneaky one]

I'm glad that I had the wknd. off! Many more variables can be added to this to complicate it to the point of - huh???? John's design has merit., I met him- we chatted of this.

I think that the outcome will be , what the manufes. see as a potential market - down the road, not just a flash in the pan round- But a huge success, civilian, or military uses . Combined technologies.
It has to be just right, --Yes I agree on the military's needs for a penetration-fmj style of a bullet-- & the potential needs of a -semi long range hunter, yet most shots at medium sized game are inside of 300yd. Deer have been taken with- less than the Grendel... for decades-- we know the drill....let's let things pan out... let's see what shows up next...hmmmm

My thoughts are still in the mid weight cals.,, with a variety of loadings - from lite to mid heavy. Basically, 78-105 grn. In the mono's., and 95-115 in the bonded units.

[Bigfoot]

Well lets try to uncomplicate it. The idea is sound. What needs to be done is make a couple prototypes and shoot them over the chrono to 500 yards and note the drops which will tell you the BC and velocity there. If you decide that it needs more intitial velocity you can either shorten the BT or design it around a shorter projectile.

130 Berger VLD length 1.4" BC .552
123 Scenar length 1.3" BC .547
123 A-Max length 1.24" BC .510

Are all good profiles. The Scenar or the SST might make the best compromise between powder space (velocity) and BC.

After that you tune the nose cavity to expand 1.5 times at the velocity at 500 yards. Done.

I agree with you that from a manufacturers POV it would sell better if the min expansion velocity was 1700 or so for sales in faster cartridges. Lets hope the BC is high enough to allow that change.

EDIT: New thought. If it matches the AMAX profile it would make a lot of 65G loaders very happy. The BC will be less because of the grooves but it would make set-up every easy. And the velocity would make up for the lower BC out till--I don't know, cause I don't know the BC but it'll be a long way out. Imagine having a coyote/target bullet, a conventional hunting bullet and a fast mono all with the same profile. That are all usable in faster cartridges. That might sell, possibly from Hornady.....maybe they would then make a long nose 110(?) Interbond with the SST profile to round out the bullet range!!!!

[BluntForceTrauma]

Hornady definitely likes to have a common ogive/nose between their lead-core and monolithics, although I still want a new hybrid VLD. "Do it right the first time" because, in industry, the inertia of start-up costs means you typically get only one chance to do it right.