stanc Wrote:...I don't understand how plastic-cased 5.56 or 12ga mini-grenades have any relevance. :confused:

Tony Williams Wrote:There's a theory doing the rounds of ammo development people in the UK that a long, pointed bullet will yaw more rapidly and reliably on impact than a short stubby one, because the if the bullet strikes with even a very small degree of yaw already (as most do), all of that mass much further back will make it a lot more unstable. I don't know if they've done any practical testing to demonstrate, that, though...

Quote:...I think that the construction and internal weight distribution has a greater effect than the shape. Just look at the difference between the yaw performance of the steel-cored 7.62x39 bullet compared with the Yugo lead-cored.

JASmith Wrote:The relevance is that one absolutely needs to understand the competition.

Tony has discussed and provided enoiugh documentation for plastic cased ammunition enough that we really need to accept that these things will be perfected before LSAT. His argument is that this gives the community a chance to use their availability as a lever to introduce a new caliber.

12 gauge grenades can give an alternative infantry-friendly path for punch at ranges of about a kilometer. The point is that, while currently less credible than plastic-cased 7.62 or 5.56 cases, these guided grenades will be looked at as the mix changes.

stanc Wrote:...but I still don't see how it's relevant to the design and development of a new intermediate cartridge...

JASmith Wrote:It becomes critically important if you want to take the design beyond the dilettante's wildcat cartridge and get a life in either the military or commercial worlds.

The design will have to reflect the marketing realities of one or both of those worlds.

Tony Williams Wrote:Thanks for doing that, very interesting. That seems to give us more leeway to play with different bullet weights than I had thought.

stanc Wrote:...In what way(s) does it (the competition) affect choice of caliber, bullet type, muzzle velocity, or any other aspect of the cartridge design?

JASmith Wrote:LR1955 has pointed out that we need "a 50%" improvement to get attention. We haven't yet identified anything that is even a 5% improvement...

Find a design combination that meets Gene's 50% plus-up in at least one aspect while maintaining rough parity in other performance factors and numbers, then you have a chance...

stanc Wrote:...From .50-70 to 45-70 to .30-40 to 30-03 to 30-06 to 7.62x51, the Army made only "5%" improvements. (5.56x45 was forced upon them by the SecDef, so it's an anomaly in the historical trend.)

JASmith Wrote:I'm sure that Gene's 50% is more rhetorical than not. The facts are, however, that we will gain exactly zero traction if we are able to demonstrate only a 5% improvement absent a political decision to go to a new cartridge.

Also, the move from each of the cartridges to the next in the list had more than 5% improvements in one or more metrics. For example, the .45-70 had a slight improvement in velocity for a significantly smaller case. The .30-40 Krag had, IIRC a 220 grain bullet replacing the 400 grain+ 45-70 bullet and a lot more cartridges, and so on.

So yes, the improvement in some metrics in each of these may have been flat or a slight improvement, there were almost always significant improvements in one or more metrics. The exception may have been the 7.62X51 -- the improvement was in weight of brass and a mild reduction in recoil at the expense of a slight reduction in velocity. The political issue was imposing a common cartridge on NATO and getting everyone to go with our beloved 30-06 would not have worked.

Quote:SecDef imposed the 5.56 DoD-wide because his metrics told him there was much more than 50% — doubling (100% improvement) the numbers of rounds per pound.

stanc Wrote:First, that's only Gene's opinion.

Second, history says he's wrong.

From .50-70 to 45-70 to .30-40 to 30-03 to 30-06 to 7.62x51, the Army made only "5%" improvements. (5.56x45 was forced upon them by the SecDef, so it's an anomaly in the historical trend.)

LR1955 Wrote:I am not sure it is a good argument to propose that just because history indicates we screwed up so many times, that we should just continue to follow historical trends.

stanc Wrote:Gene,

I don't know if all of those changes could rightly be judged as "screw-ups," or not. What I'm saying is that, when it comes to what they'll probably find acceptable in the present (and future), look at what their SOP has been in the past.

The only exception to this rule that comes to mind is the Stryker. Prior to Shinseki's reign as Chief of Staff, the Army's leadership was absolutely and fundamentally opposed to wheeled armored infantry vehicles. In spite of that institutional opposition, he managed to get it adopted.

Now, it could be you're right that any new small arms cartridge would have to deliver a "quantum" improvement. Since I can't read their minds to know if that's what they want, it seems logical to me to go by what they've habitually done before.

LR1955 Wrote:I never noted anyone in the RD arena willing to put money into something unless it represented a very significant improvement over what we have now.

Quote:Although I do not know if any requirements exist for a new cartridge, my bets are that if one does exist it stipulates a statistical improvement in one or more areas over what exists now. And that such improvements are part of an overall system that includes the weapon and sighting system.

Tony Williams Wrote:True, but the situation continues to evolve. The widespread distribution of 7.62mm rifles and MGs down to section level (helped by the fact that the British have just joined the US in selecting the 7.62mm Minimi) has to a large degree addressed the range and (to some extent) the effectiveness issues of 5.56mm, but has created a new problem - ammo weight!

stanc Wrote:I presume they shoot standard NATO ball ammo in the L129A1 rifle? Do you know what muzzle velocity is from that 16" barrel? Maybe 2600 fps?

JASmith Wrote:Tony, You've done very well at positing the next family of weapons and ammunition, but an immediate step to that family may be larger than can be swallowed just now. Try to think incrementally from where we are today and where we need to go.

Tony Williams Wrote:I am, which is why I keep plugging the idea of firming up on the required calibre and ballistics using conventional technology first (preferably fielding some weapons in the new calibre for thorough testing), then transferring the lessons learned to the next phase of LSAT development.

If LSAT fails, then we can look at introducing the new calibre in conventional form but probably using lighter case materials (part-polymer, stainless steel and light-alloy are all being worked on at the present time).

• Only 5.56x45 should be replaced.
  
• Only 7.62x51 should be replaced.
  
• Both 5.56x45 and 7.62x51 should be replaced.
  

stanc Wrote:I think this is a very good approach. However, I see a couple of problems to "firming up on the required calibre and ballistics."

1. There is no consensus as to whether:

• Only 5.56x45 should be replaced.
  
• Only 7.62x51 should be replaced.
  
• Both 5.56x45 and 7.62x51 should be replaced.
  

Replacing only 5.56x45 with a bigger, heavier cartridge (like 6.5 Grendel and 6.8 SPC) increases the rifleman's carry load and/or decreases the number of rounds he carries, but does not change the machine gunner's load.

Relacing only 7.62x51 with a smaller, lighter cartridge (like 6.5x45 and 7x46) decreases the machine gunner's carry load and/or increases the number of rounds he carries, but it slightly increases the rifleman's load (if he is tasked to carry extra ammo for the machine gun).

Replacing both 5.56x45 and 7.62x51 with a single, intermediate cartridge (like 6.5x45 and 7x46) decreases the machine gunner's carry load and/or increases the number of rounds he carries, but it also substantially increases the rifleman's load (especially if he is tasked to carry extra ammo for the machine gun) and/or decreases the number of rounds he carries.

Then there is the (so far undiscussed) idea of replacing 5.56x45 with a bigger, heavier cartridge (but one not as big or heavy as 6.5 Grendel and 6.8 SPC), and replacing 7.62x51 with a smaller, lighter cartridge. This would impose less penalties on the rifleman than would a "unified" caliber.

Quote:2. There seems to be almost no publicly available test data on terminal effects of "eco-friendly" military ball projectiles. Without such data, how can we possibly make a logical, rational decision as to which caliber is optimum?

Tony Williams Wrote:I don't see much prospect of a new round just to replace 5.56mm. The counter-argument will always be that 5.56mm is normally good enough (especially given M855A1 or MK318) and for circumstances in which it isn't good enough, there are 7.62mm weapons available.

Replacing the 7.62mm with a lighter round of equivalent long-range performance is likely to be more attractive to the army (US or UK) since they are very concerned about reducing the huge burden carried by dismounted troops.

By definition, a lighter, smaller-calibre long-range round to replace 7.62mm would also generate less recoil. Having tried HK 416 in 5.56mm and 6.8mm plus HK 417, all in quick succession, I found that the perceived (as opposed to calculated) recoil of the 6.8mm was much closer to the 5.56mm than to the 7.62mm. This makes a long-range intermediate round of similar power a realistic proposition for replacing 5.56mm in rifles and carbines. Yes, there would be some penalty in ammo weight (or alternatively the infantryman would carry fewer rounds) but the greater range and effectiveness of the ammo might well trump that.

Quote:All I've seen are assurances that the M855A1 and the British 5.56mm HP produce more consistent terminal effects, but no evidence in support. But ARDEC did all the testing in different calibres using military-style green bullets and concluded that 6.8mm was best...

stanc Wrote:Since the ballistics tables I ran a few days ago show a match to 7.62mm trajectory and wind drift with both 6.5mm 110gr and 6.8mm 120gr (and probably also with a hypothetical 7mm 130gr), I guess the next question is, what trade-off between cartridge weight and terminal effects is acceptable?

If minimum weight/recoil is desired, and minimum effectiveness is acceptable, go with 6.5mm. If maximum weight and recoil is okay in order to achieve maximum target effects, 7mm is the best choice. As with the SPC, 6.8mm would be in between 6.5mm and 7mm, both in weight, recoil, and terminal effects.

Unless priority is placed on really minimizing weight and recoil, 6.35mm and 6mm are probably not worth considering. The farther down we go from 7.62mm, the farther away we get from 7.62mm destructive ability.