Aluminum Cased Ammo

CCI began selling "Blazer" aluminum cased ammo over a decade ago. A G2mil reader asked why no military has begun to use aluminum cased cartridges since they are much cheaper to produce than brass, which is mostly copper. Moreover, aluminum cases are one-third the weight of brass, so a couple hundred rounds will weigh a pound less. This may not seem great, but for grunts who must "hump" heavy packs, every pound matters. If aluminum cases are used for heavy machine guns, the weight and cost savings are much greater.

I scoured the Internet with a Google search for: CCI Blazer There are some who think it is better and others who think it is slightly worse. I asked some experts and no one knew why it has not been adopted. Stan Crist said the Army developed steel and aluminum cased rounds for the 6mm SAW program; that gun was not adopted. I suspect lobbyists from the "brass industry" have discouraged adoption of aluminum cased rounds for government use. Someone with influence needs to nudge to the US military to test this idea. CCI has been producing them for several types of guns for years so we know it works.

A recent University of Ohio study of metal properties concluded:

"Aluminum showed a definite edge over copper in the simulations. It proved to be 32 percent stronger than copper, and it endured much larger shear strains before it began to soften. ... We know copper is three times heavier than aluminum, and significantly stiffer than aluminum under normal conditions. But when we looked at large shear strains, aluminum won hands down. Copper started out stiffer, but it softened earlier than aluminum."

Carlton Meyer editorG2mil@Gmail.com

Letters

Aluminum casings are strong, but ...

While aluminum may be comparable to brass in terms of mechanical strength, it is inferior in other respects. Most importantly, its volumetric heat capacity is only three quarters that of brass. A lot of the waste heat produced when a round is fired is carried away in the hot casing itself. The lack of such cooling was one of the factors that caused the failure of the H&K G11 caseless assault rifle program. If an aluminum case of the same shape were used instead of a brass one, the chamber of the weapon might overheat and cause ammunition "cook-off".

In a semi-automatic weapon like a hunting rifle or handgun, overheating is not a significant problem, which is why the CCI Blazer ammunition is OK. In an automatic weapon, chamber overheating is a dangerous possibility, particularly in machine guns which tend to run hot anyway. Using aluminum cases would an enlargement of the casing to ensure enough cooling. While you would still have a little on material cost and weight with the larger aluminum cases, the cost to rechamber existing weapons to use the new rounds completely negates these savings.

This is an explanation that I thought of myself after reading about the development problems of the G11,.so there is no study I can cite. Hot casings extract as much as 80% of the heat from the chamber during firing, and the G11 needed to have a special low-temperature cook-off-resistant propellant developed for it.

While this suggestion does not seem feasible, it is in the minority on this site. I find your suggestions on improvements to the military to be the most innovative and thought-provoking on the web, and I hope you keep up the good work.

David Khoo

Ed: Phil West heard the G11 rifle worked, but Germany didn't want to fund it after the Cold War ended.

30mm Aluminum Cased Ammo

IF REDUCED AMMO WEIGHT IS THE GOAL, THE SMART THING TO DO (IF POSSIBLE) IS TO DESIGN FOR ALUM’M CASES WHEN THE GUN/AMMO ARE FIRST DESIGNED TOGETHER – AS A SYSTEM. WHICH IS WHAT THE AF DID WITH THE GAU-8/A 30MM GATLING [used by the A-10 attack aircraft], AND WHICH HAS USED ALUM’M CASES SINCE “DAY ONE.” GAU-8 CASES BY THE WAY ARE A SPECIAL ALLOY CONTAINING A LITTLE SILVER. THAT’S NOT GOOD FOR COST, BUT THE CASES ARE RECYCLED EASILY SINCE THE SPENT CASES ARE NOT EJECTED FROM THE LINKLESS AMMO SYSTEM.

DESIGN PROBLEMS AND CHALLENGES VARY ACCORDING TO WHETHER ONE IS TALKING ABOUT SMALL ARMS, AUTOCANNONS, OR ARTILLERY-CALIBER WEAPONS. ALSO, WITHIN THOSE CATEGORIES, THERE ARE HIGH AND LOW PRESSURE SYSTEMS, AND HIGH AND LOW RATE OF FIRE SYSTEMS. FURTHER CHALLENGES ARE FOUND IN A/C GUNS, WHICH HAVE THE ADVANTAGE OF STARTING OUT ICE COLD INSOFAR AS HEATING IS CONCERNED, AND THE DISADVANTAGE OF STARTING OUT ICE COLD AS FAR AS THE GUN FREEZING UP IS CONCERNED. THE THING FOR THE DESIGNERS TO DO IS TO UNDERSTAND WHERE THE PROBLEM AREAS LIE.

I REMEMBER WHEN STEEL CC WERE INTRODUCED INTO TANK CANNON AMMO, TO REPLACE BRASS, AND SOME PEOPLE WERE HYPERVENTILATING OVER MFG AND PERFORMANCE (EJECTION) PROBLEMS. EVENTUALLY THE PROBLEMS WERE SOLVED WELL ENOUGH – EVEN THO’ BRASS IS/ WAS A LOT EASIER TO MAKE WORK THAN STEEL. THAT MAY NEVER CHANGE, AND 120MM ALMOST-CASELESS TANK AMMO BRINGS ITS OWN CHALLENGES.

ALUM’M CASES WORK WELL ENOUGH IN 40MM GRENADES (LOW PRESSURE AND LOW ROF) AND I BELIEVE THAT ALUM’M CASES HAVE BEEN USED IN PISTOL AMMO. ONCE AGAIN, LOW PRESSURE AND LOW ROF. ALUM’M CASES WORK VERY WELL IN GAU-8 SYSTEMS, HIGH PRESSURE, HIGH ROF, AND ICE COLD AT THE BEGINNING OF A BURST. THAT THE GUN HAS SEVEN BARRELS HELPS A LOT, TOO.

ONCE UPON A TIME, THE ENGINEERS AT AEROJET GOT AN ARMY CONTRACT TO MAKE AN EXPERIMENTAL CTDGE FIRING MULTIPLE FLECHETTES AND WERE REQ’D TO USE AN ALUM’M ALLOY CASE. THE ARMY ENGINEERS WERE ALL WRINGING THEIR HANDS ABOUT ALUM’M CTDGE CASES AND THEIR PROBLEMS. WE RESEARCHED THE LITERATURE AND FOUND THAT THEIR WORK WAS LIMITED TO 6061-T6 ALUM ALLOY.

WHY? BECAUSE OF COST, THAT’S WHY. SO THE CONCLUSION THEY CAME TO WAS THAT ALUM WAS INFEASIBLE FOR HIGH PRESSURE SYSTEMS, WHEN THE CONCLUSION SHOULD HAVE BEEN THAT 6061-T6 WAS NOT THE RIGHT ALLOY FOR SUCH AN APPLICATION. WE PROCEEDED WITH ANOTHER ALLOY. WITH ALL THE PROBLEMS WE HAD ON THAT JOB, THE ONLY PROBLEM WE DIDN’T HAVE WAS WITH THE ALUM’M CTDGE CASE.

I THINK THAT THE ISSUE OF “ALUM TO REPLACE BRASS OR STEEL?” SHOULD BE REPLACED BY THE ISSUE OF, “WHAT’S THE BEST CC MATERIAL TO USE IN THIS SYSTEM, CONSIDERING GOALS FOR PERFORMANCE, COST, WEIGHT, RELIABILITY, AND SPECIAL FACTORS? SPECIAL FACTORS INCLUDE ROF, MUZZLE VELOCITY, HOW AND WHERE THE WEAPON WILL BE USED, AND BY WHOM, + ENVIRONMENTAL FACTORS.

Don Loughlin

Ed: Since the A-10s gun is a seven-barrel rotating gatling gun, this provides extra cooling.

Heat Extraction

I have a fairly uninformed speculation for one reason aluminum may have problems as a military ammunition case material: heat dissipation. My understanding is that the brass cartridge is a fairly significant carrier of firing chamber heat out of the gun. (If I remember discussions correctly, this was one of the hidden issues H&K ran into while developing the G11 and its caseless ammunition.) If aluminum is a less efficient carrier of heat than brass, this could be a not insignificant problem.

This (if true) is presumably not a problem in civilian firearms, which I suspect that the CCI Blazer rounds are designed for, since I expect that they usually fire slow enough to dissipate the heat anyways. I would expect this to be a potential issue in military weapons fired semi-auto or full auto, and possibly even if a significant amount of a magazine is emptied as fast as possible in single-shot mode.

CKS

Ed: Stan Crist asked the CCI technical services people why they didn't make 5.56mm aluminum ammo, and they didn't know! A .22 caliber adapter is sometimes used to train because the 5.56mm ammo is too expensive. However, rifle range training is always slow, single-shot training. Perhaps they could use half-price aluminum cased ammo at training ranges.

Aluminum was tested in the 60s

There is presently not an aluminum alloy-that I know of-that can consistently withstand the chamber pressures generated by modern high power rifle cartridges. When aluminum cased rounds are fired with high chamber pressures the expanding gases can, on a random basis, create a high velocity flow path of molten metal through any structurally weak points in the case (either caused by damage or design) and the high temperatures of the propellant gases can actually ignite the aluminum particles and cause a complete burn-through and fireball within the weapons chamber with resultant catastrophic results. This flow or venting usually takes place through the case head, around the primer or if there are folds or scratches, on the case body side walls. There have been developed ways to prevent burn-through by using liners and coatings inside the case, but they add to the cost of manufacture and take up powder space which usually causes an unacceptable reduction in pressure and velocity.

Frankford Arsenal, during the 1960's, had a major development program directed at aluminum alloys and aluminum cases for 5.56MM and 7.62MM ammunition, but after a 5-year effort could not solve the random burn-through problem. The Arsenal concluded that eventually higher-strength aluminum alloys would be developed by industry that would solve this problem, but to date, none that are cost effective have been made available that I know about.

As you know, aluminum cases have been used with success in lower pressure pistol and revolver cartridges (apparently with chamber pressures below 40,000 psi the burn-through phenomenon does not take place). Aluminum cases have also been used effectively in medium caliber cannon and artillery rounds when weight is a prime consideration.

Frank Hackley

Ed: I'd think that 40 years after the Frankford programs, the US Army could spend some money to study cheaper, lighter casing alloys. The Army spends almost zero on new small arms. The M1A2 was developed by Marines at Quantico with spare funds. All modern light machine gun designs come from Belgium, yes Belgium!