Long Light Bullets (e.g., Spanish CETME and US FABRL) a dead end?

[Essayons]

This isn't 6.5 Grendel specific, and probably wouldn't work withing the cartridge overall length limits for the 6.5 grendel in AR15 magazines, but both the Spanish and Americans achieved promising results in terms of external ballistics versus recoil wile experimenting with long light bullets. I'd like to know what Tony Williams and others here think of this idea. Was it an evolutionary dead end? Or might we still see some variation of this idea implemented?

I found this paragraph related to the 7.92x40 CETME round on Tony's website:

"One cartridge worth its own paragraph was the Spanish 7.92x40 CETME Model 53. The ammunition was designed by Dr Gunther Voss, a German ballistician working for CETME. He wanted to combine a good long-range performance with light recoil, which he achieved by using a 6.9 g (106.5 grain) bullet made from solid aluminium alloy except for the copper sleeve around most of its length, which compensated for its light weight by being highly streamlined. As a result, it achieved a ballistic performance comparable with the 7.62x51 (MV was 800 m/s from a carbine-length barrel of 435mm) with a significant reduction in ammunition weight and an even bigger reduction in recoil."

Tony also mentions it at http://www.dtic.mil/ndia/2015/smallarms/...lliams.pdf.

There's an interesting document on the US FABRL round at http://www.dtic.mil/dtic/tr/fulltext/u2/765459.pdf.

"The FABRL concept could result in a considerably lighter system while still maintaining the same muzzle velocity and trajectory as the M193 ball bullet. The required chamber pressure of 39, 500 psi could enhance the feasibility of utilizing lightweight case materials for a future system. Even if a brass case was required for the FABRL cartridge, overall cartridge weight should be reduced by approximately 30 percent from that of the 5. 56 mm M193 cartridge."

[BluntForceTrauma]

I want to discuss this, as well. Fascinating concept. I approach it from the angle of trying to get the best external ballistics from mass-produced, hardened steel core general-purpose bullet for something like the 65G.

My concept is a steel arrowhead like M855A1 — but with a longer tail — set into what is, basically, a solid copper "sabot."

I'm not wild about the super light alloys such as aluminum because I'm skeptical of their penetration in general-purpose combat scenarios.

Density of lead is 11.34 g/m3. Density of copper is 8.96. Steel 8.0. Aluminum 2.7 — if memory serves.

[stanc]

I want to discuss this, as well. Fascinating concept. I approach it from the angle of trying to get the best external ballistics from mass-produced, hardened steel core general-purpose bullet for something like the 65G.

My concept is a steel arrowhead like M855A1 — but with a longer tail — set into what is, basically, a solid copper "sabot."

Sounds similar to the Swiss RUAG 7.62x51 AP bullet design?

I'm not wild about the super light alloys such as aluminum because I'm skeptical of their penetration in general-purpose combat scenarios.

You're right to be skeptical.

IIRC, several years ago Frank Hackley (Frankford Arsenal's last commander) told me that the plastic-core bullet in 5.56 FABRL had very poor penetration capability vs lead-core M193.

TFB article on the 5.56 FABRL: http://www.thefirearmblog.com/blog/2014/...6mm-fabrl/

[stanc]

This isn't 6.5 Grendel specific, and probably wouldn't work withing the cartridge overall length limits for the 6.5 grendel in AR15 magazines, but both the Spanish and Americans achieved promising results in terms of external ballistics versus recoil wile experimenting with long light bullets. I'd like to know what Tony Williams and others here think of this idea. Was it an evolutionary dead end? Or might we still see some variation of this idea implemented?

Dead end, IMO. Hard target penetration was rather poor for use as general purpose ball. And IIRC, there were stability issues with the very high L/D projectiles.

[Essayons]

I want to discuss this, as well. Fascinating concept. I approach it from the angle of trying to get the best external ballistics from mass-produced, hardened steel core general-purpose bullet for something like the 65G.

My concept is a steel arrowhead like M855A1 — but with a longer tail — set into what is, basically, a solid copper "sabot."

I'm not wild about the super light alloys such as aluminum because I'm skeptical of their penetration in general-purpose combat scenarios.

Density of lead is 11.34 g/m3. Density of copper is 8.96. Steel 8.0. Aluminum 2.7 — if memory serves.

Take a look at page 18 of the Frankford Arsenal paper I linked above.

I also agree about penetration or aluminum/plastic cores. The Frankford Arsenal paper shows variations that include steel, lead and even uranium to enhance penetration, though. See pages 17-27 of the linked PDF file.

[BluntForceTrauma]

Sounds similar to the Swiss RUAG 7.62x51 AP bullet design?

Boom, yes! Almost exactly it. Now just Grendelize that baby!

But tweak it so there is a bit more copper in the boattail, sort of like Nosler's Accubond LR. That way you'd have a bit more weight in the tail to promote both external ballistics and tumbling in soft tissue.

Did a search and realized I was advocating this bullet a while ago. Post #388.

[stanc]

Did a search and realized I was advocating this bullet a while ago. Post #388.

I'd completely forgotten about that. Looks like it might be a good concept, John. Gonna make some?

[BluntForceTrauma]

I'm currently working on a solid copper projectile that, at least, will incorporate my idealized form factor. Will also be testing yaw in gelatin. Few months out, though.

[ah1whiskey]

i'm kicking around a 6mm-grendel with 105s.

a m855/ss109 style bullet in 6mm would be fun!!

long and light might work providing its not too light.

maybe a steel core or "other" core in a lead 6.5 that has the same length and BC of the 144 --?? or even longer?

still got to fit the ar mag though--lol