6mm MIKE

My original idea in this article was to increase the performance of weapons designed for the .30 Carbine round by fitting the case with a .224 bullet. (All centrefire rounds of a nominal .220-.225 in fact use a .224/5.66mm bullet, including the .223 Rem/5.56x45mm).

I originally thought of the .224 bullet due to being aware of the work done on the 5.56x30mm MARS round and because bullets in .224 were widely available.

One problem with the .224 is that it is very dependent on velocity for its terminal effects, at least in FMJ configuration.

An alternate idea that has recently occurred to me is to mount a 6mm/.243 bullet in a M1 Carbine case.

These bullets are available in 100-115gr weights, the same weight as .30 carbine bullets but with superior aerodynamic shape, sectional densities and ballistic coefficients.

Weights of 70-95gr may prove more suitable for a police role and bullets as light as 55gr can be found.

While a 6mm 55gr bullet has a lower sectional density than a .223 (.133 vs .157), it has still has a better ballistic coefficient (.276 vs .235).

95-100gr 6mm bullets have Sectional Densities of .230 to .242, much higher than the .178 of the M855 or the .221 of the 147gr 7.62x51mm NATO. That means the round will have very good penetration.

Some rough calculations suggest that a 100gr bullet with a BC of .351 and a V0 of 1,900fps would shoot point blank to 209yds with a 15/178yd zero, hit less than a foot low at 250yds, and take half a second to reach this distance. Energy levels are similar to the 5.56mm MARS but with the advantage of a larger calibre denser bullet.

100gr 6mm	Range
Range - yds.	0	50	100	150	200	250	300	350	400	450	500
Velocity - ft./sec.	1900	1797	1697	1602	1513	1429	1350	1278	1215	1158	1109
Energy - ft.-lbs.	801	717	639	570	508	453	405	363	328	298	273
Path - in.	-1.5	2.6	4.0	2.4	-2.6	-11.4	-24.5	-42.4	-65.5	-94.6	-130.1
Time of flight - sec.	0.0	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.1

Best Zero Results
Near-Zero - yds.	15	Midrange - yds.	99
Far-Zero - yds.	178	Max Ordinate - in.	+4.0
Point-Blank - yds.	209	Target Diameter	8”

Zeroed to 200yds a 55gr 6mm bullet of BC .276 and V0 2,790 fps raises no more than 2” above the line of sight, giving it considerable potential as a police marksman's round in built up areas.

55gr 6mm	Range
Range - yds.	0	50	100	150	200	250	300	350	400	450	500
Velocity - ft./sec.	2790	2625	2466	2313	2166	2024	1888	1758	1634	1519	1413
Energy - ft.-lbs.	950	841	742	653	573	500	435	377	326	282	244
Path - in.	-1.5	0.9	2.1	1.9	0.0	-3.7	-9.6	-17.9	-29.0	-43.4	-61.5
Time of flight - sec.	0.0	0.1	0.1	0.2	0.2	0.3	0.4	0.5	0.6	0.7	0.8

Note that according to the chart published in Jane's Infantry Weapons 1976, 72% of all rifle engagements are at 200m or less.

An M1 carbine casing is 33mm long, although this may need to be shortened to accommodate the 5.56mm or 6mm bullets. The overall length of the final round should be 42.67mm, same as a .30 round.

M1 carbines are not as common as they once were, which rather negates the basic .223/6mm MIKE concept.

A niche of a round optimized for shooting at 200 metres or less remains. The low mass and recoil of such a weapon has obvious appeal to police officers and civilians who do not have time to spend hours on the rifle range.

Logically, I find myself coming full circle with the idea of mating a 6mm bullet to a .221 Fireball/shortened .223 case. This already exists in the form of JD Jones’ 6mm Whisper, which despite the name may be loaded to supersonic velocities.

Information sent to me personally by JD is that a 90gr bullet from a 16.5 inch barrel achieves 2,150fps, a 115gr 2,086fps and a 65gr 2,541fps. Subsonic loadings offer increased potential for this weapon system.

The 6x35mm round used in Knight Armaments PDW is essentially a 6mm Whisper.

.223 MIKE

The M1 carbine was created as a self protection weapon to offer better performance than the M1911A1 pistol and Thompson SMG.

It was intended to arm mortar men, drivers and other non-front line personnel but it was not long before it was being used by combat troops in a more aggressive role.

Reports on the .30 M1 carbine in combat inevitably speak of its woefully poor stopping power.

The weapon itself, however, was well liked for being so handy. It has been described as a useful weapon for night patrols and repelling mass attacks.

An interesting piece of advice I've come across was that if you thought of the .30 M1 carbine as a rifle, you would always be disappointed. Better to think of it as a “two-handed pistol”

In summary, users liked the M1 carbine but the round was often found wanting.

In 1963 the 22 Spitfire round was created using an M1 carbine case. This fired a 40gr bullet at 3,000 fps.

The round underwent military trials and performed well out to 300yrds. Zeroed to 200yds the round only dropped 12.6" at 300yds.

One might assume from the weight that the bullet of the .22 Spitfire was a 22 roundnose, but Stan Crist has informed me that the 22 Spitfire did in fact use a lightweight spitzer round.

Johnson adverts describe the rounds as using a .223 bullet and there is some resemblence to the pointed bullets of the .22 Hornet.

With such a light round, target effects are likely to have been poor.

5.56x30mm Mars

In the 1990s, Lt Col Michael Harris, recently retired from the Green Berets, pushed the idea of a personal defence weapon which would be better than the M9 pistol and MP5 (this concept may sound a little familiar!).

Harris talked Colt into making a 5.56x 30mm round chambered in a gun described as “Honey I shrank the M4 ”.

The MARS shot really well and had 2.5 times the power of a 9mm.

It was rejected on logistical grounds.

Data sent to me on the original 5.56x30mm is that it used a 55gr bullet at 850m/s (2790fps).

There is also mention of a tungsten “dart”with a brass surround which could penetrate both sides of a kevlar helmet at 300 metres.

When I heard about the MARS project, it occurred to me that a similar round could be created by placing a 5.56x45mm bullet in an M1 carbine case.

This would effectively be the 5.56 x 30mm round, differing only in the casing used.

The ballistics would be as established for the MARS but the round could be fired by any rebarrelled M1 carbine.

This idea offers a big upgrade in M1 performance for just a new barrel. Rounds and brass are readily available.

The result is a rifle perfect for ranges under 300 yards, which is a far as many of us can see or shoot anyhow.

By using a spitzer round, we can expect a better energy retention and flatter trajectory than either 22 Spitfire or .30 carbine round.

Assuming the same performance as the MARS, this would mean a 50% increase in muzzle energy, and the proposed 223 Spitzer will have a far greater target effect, even in FMJ.

When I first considered the idea of a 5.56x30mm converted to M1 carbine brass, I didn't really think of it as a combat weapon, although its home defence potential did briefly occur to me.

I begin to reconsider when I passed the suggestion on to the Weapons list, asking what people would use it for.

Much to my surprise, an ex-SWAT guy was very much in favour of it as a patrol carbine.

“Well, it wouldn't make a bad urban style rifle. We're issued the AR15 collapsible stocked carbine in 9mm for carry in the cruisers. Fun gun, like shooting a .22. Takes a real nimrod not to qualify with one. It's just that the ballistics aren't improved that much, MAYBE 150fps. Lets not forget also that the M1 carbine action was so endearingly reliable as well.”

The 223 MIKE round would also have 250% more muzzle energy than a 9mm, and better energy retention and flatter trajectory characteristics too.

The spitzer configuration would also give it better capability against body armour and more reliable wounding effects, utilising tumbling rather than just mushrooming.

Most likely loading for police use will be the same bullet as used in the Federal 55gr Tactical JSP 5.56x45mm round. This is reported to offer very impressive terminal effects, even when fired from short barrelled weapons.

Some data I've found for the Federal 55gr JSP in 5.56x45mm configuration indicates that fired at a V0 of 2,854fps, it will penetrate 16.8" of calibrated ballistic gelatin. That muzzle velocity does seem a little low for a 5.56x45mm of this weight . A .223 MIKE could probably equal this velocity and some 55gr loads of .221 Fireball already exceed this.

From the same source I found that a Win 50gr JSP fired from a 5.56x45mm at 3,163 fps produced 12.4&quor; penetration. 12.4" of penetration is still viable for combat and that round has a lot of energy which it loses to the target in a very short space of time. With a 50gr bullet the 221 Fireball can reach 3041 fps from a 24&uote; barrel.

The 223 MIKE would be effective at the 200m ranges that some police departments desire, but would be less dangerous to bystanders since it hasn't the 800m+ potential of the 5.56x45mm.

Ironically, an M1 carbine is not perceived by most people as a “military weapon”.

Personally, I though the .223 MIKE might make a nice hunting and varmint round. Such a lightweight but capable weapon may find favour with backpackers, explorers, yachtsmen, and anybody else who needs a lot of gun in a small space.

The weapon may see service as an aircrew survival arm. Another advantage of this calibre is that the carbine can also fire 22 LR or 22 Magnum ammunition by using chamber adapters.

Theoretically, any M1 carbine could be converted to 223 MIKE by just changing the barrel. In practice, M1 carbines are not as common as they once were, so new weapons may need to be built to exploit the potential of the round.

Variants

The most obvious model to have is a reproduction of the M1 carbine in the new chambering. By using new materials such as synthetics it may be possible to reduce the weight even further.

A weapon based on the Ruger PC carbine series is a possibility.

The police potential of the weapon may call for the incorporation of such features as tritium sights and flashlights.

A low power scope (such as a 2.5x) improves target view in low light conditions without slowing the shooter down.

There may even be a police version with an underbarrel 37mm tear gas grenade launcher.

As well as the traditional configuration, it did occur to me there may be a demand for a weapon with a straight-line layout.

My sketches of such a weapon usually look like the Czech Vz 58 Assault rifle, which itself that looked like a more elegant AK.

This won't have to fire spigot grenades, so the sight can be right up at the muzzle, which with a receiver sight will give a long sighting radius.

At least one manufacturer of M1 carbines toyed with the concept of “M16-style” versions.

The assault pistol version was interesting : an M16-style front sight and a Thompson-style fore-end.

Another potential variant is a straight-line carbine with a heavier barrel and bipod: essentially a very compact LMG. This is similar in concept to the HK G8 Police Rifle, which had the potential to function as either a sniper weapon or LMG.

Such a weapon in .223 MIKE might be useful for firing from a vehicle, house to house operations or patrolling.

A useful weapon against roadblock runners possibly?

In Germany, customised .30 M1 carbines were issued to police marksmen. This may be another role for the heavy-barrelled version.

The Ukrainians have the Yesaul (right), an anti-personnel/anti-material revolver chambering the 5.45x39mm assault rifle round. A similar weapon could be created in 223 MIKE based on a weapon like the Ruger Redhawk, Blackhawk or this experimental S&W.

Such a pistol would also be useful for long-range shooing.

This revolver may be one of the few weapons of the class ever seen with a flash suppressor.

An alternate idea is to make an assault pistol based on one of the above proposed rifle designs, in the same way as was done with the .30 M1 Carbine Enforcer pistol.

A weapon this small and that potent may make a good concealable/clandestine weapon for special forces. Performance against body armour will certainly be better than weapons such as the FN P90.

It may be possible to make barrels easily changeable so that an officer can carry in his patrol vehicle a carbine that can be reconfigured as a short-barrelled CQB/tactical entry weapon when needed.

FEEDBACK

Phil, it occured to me while reading this that an even easier solution is to just load your proposed bullet into the .30 carbine case using the plastic sabot that Remington used for the .30-06 Accelerator loads (5.56mm bullet in '06 case.) Just use the new round in a regular M1 Carbine.

John

Only difficulty in using saboted projectiles in autoloaders is the pressure curve: it can be too abrupt a spike to make the action function (thanx and a tip of the hat to Ian V. Hogg, who mentions this discouraging fact). Still, this might be workable w/ tinkering.

Ed

UPDATE: Does the .223 MIKE already exist?

While reading about the .300 Whisper round for the M16/AR15, I noticed that .221 Fireball brass was used to make this round. I also seem to recall something about the case for the 5.56x45mm round having a streak of M1 carbine brass in its ancestry. However, rim diameters and some other dimensions are different.

Jane's Ammunition Handbook gives the head diameter of the M1 Carbine round as being 9.1mm and the 5.56x45mm as 9.5mm. This suggests that weapons designed for the M1 Carbine round could with minimal modification accommodate rounds based on shortened 5.56x45mm brass.

The .221 Fireball uses the same round as the 5.56x45mm in a shortened (35.56mm) case. Performance seems similar to the 5.56x30mm MARS round.

Would it be possible to use the .221 Fireball with a 55gr in an M1 Carbine-type police weapon?

This article suggests a compact rifle chambering .221 Fireball as a Close Quarter Battle (CQB) Rifle.

I have also seen other writers suggest that for urban combat what is needed is a high penetration round that can be carried in even greater quantities than the 5.56x45mm.

The author also suggests a 6mm main battle rifle. My preference for the latter is for a 6.5-7mm weapon. More details on that topic here:

The result was what we called the “Whippit” because all you had to was shove down with your right hand and whippit out, shooting. I have also seen a carbine with a stud embedded in the stock, which fit a clip on the pistol belt.

Only just got to read the lattest version of the .223 mike article, have one addition. Am reading the new edition of Bruce Canfield's “The Complete M1 Garand and M1 Carbine”, Canfield states that the Carbine's short-stroke gas system is not as subject to pressure curve problems as other systems of gas operation.

PW: I'd guess that this is probably because the action of the M1 carbine tappet on the bolt is more of a “flick” than a push. It is possible that both M1 carbine “Accelerator” ammo would be available alongside Carbines chambered in .223 MIKE/.221 Fireball. I'm sure some shooters would want to use .223 rounds for hunting and .30 JSP/JHP for home defence, even though the effectiveness of the 125gr .357 to which the .30 JSP/JHP round is usually compared has been overrated due to Marshall and Sandow's poor statistical design.

At the moment, I can see two major forms of new carbine.

One would be a police and civilian model with a traditional style stock and “non-military” look.

The second would be a folding stocked straight-line military weapon, maybe looking like a “Honey I shrank the AR-18”.

Heavy-barrelled and pistol versions would also be available.

Using the Ballistic Calculator at www.realguns.com it is possible to get some idea on how the 5.56x30mm round would have performed.

The velocity figures quoted above were probably for a 11" barrel, so a higher velocity might be found in a carbine.

I've assumed a BC of .255, although the MARS was claimed to use a .272 BC FMJ round.

The same performance from a 223 Mike round loaded to the same criteria may be expected.

As can be seen, with a 250yd zero this round can be expected to shoot point blank to 300yds.

Figures below are for .221 Fireball 50gr bullet with a BC of .238 fired from a 24" barreled rifle at 2995fps

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