I have listed below a number of different M-11 models. I have attempted to make the information as accurate as possible but this can be hard to do since there is so much misinformation out there. I am sure I missed a model or two since so many were made. If you have information on a model I missed please let me know.

We tend to generically refer to these guns as "MACs", but tecnically the term "MAC" only refers to guns manufactured by Miliary Armament Company. The true model designations tell us a lot more about particular guns and their caliber:
       M10 is chambered in either 9mm or .45acp
       M10A1A can be either 9mm or .45acp
       M11 is always .380acp.
       M11A1 is a late production RPB gun and all SWD .380acp guns.
       M11/NINE is only 9mm and only SWD produced these. Sometimes shortened to M-11/9.

NOTE: Some pictures of models have been generated by a computer so a axis pin hole might be in the wrong spot and are a result of the limited sample of M-11s I had to work with.

UPDATE NOTE: The prices shown below are out-of-date. As of early 2016, the MAC-10 submachineguns are going for around $4500-$5500. The M11/9 model value has jumped substantially, at least in part due to the availability of LAGE uppers, .22LR kits, and the CF-W slowfire bolt. The M11/9 guns are no longer the least expensive of the full-auto models, and are now selling in the $7000-$7500 price range... and I thought I was paying a lot when I bought my M11/9 and M11A1 for just under $3000 each! --Concorde
 

The M.A.C. Model 11 was the first M-11 series gun produced and is quite the collector item today. Chambered in .380 ACP, the M.A.C. M-11 uses steel magazines in either 16 or 32 round capacity. Like most M-11s it has a collapsible stock that extends from the butt of the weapon, a selector switch to fire either in semi or full-auto, uses the open bolt method of operation & the end of the barrel is threaded to accept a silencer or other barrel accessory. Compared to other M-11s, the original M.A.C. guns are generally of a higher quality.

A unique fact about the M.A.C. M-11 is the fact that the receiver says 9MM AUTO K which confused many shooters who tried to use 9MM LUGER & not 9MM AUTO K (.380 ACP).

Since not to many of these were produced because M.A.C had trouble getting them to “take off” there are not to many original M.A.C. M-11s out there. Because of this they can command higher prices because they are “collectables”.

or

INGRAM M11 CAL 9MM AUTO K
MILITARY ARMAMENT CORP.
MARIETTA, GA. U.S.A.

When M.A.C. went “belly up” in the mid 1970s they auctioned off their remaining stock of tooling & parts. The company RPB (R. Roby, C. Pitts, & R.W. Brueggemann) Industries Incorporated purchased the majority of what was left of M.A.C. including a number of finished frames. These frames had already been stamped by M.A.C. with their information, so instead of just throwing them out RPB just stamped their mark on the opposite side of the receiver. These are some times called “overstamp” guns even though the RPB stamp wasn’t stamped over any thing.

Since these “transitional” M-11s are primary assembled on frames and parts produced by M.A.C. they are basically the same gun.

The RPB “overstamp” M-11 is chambered in .380 ACP & uses steel magazines in either 16 or 32 round capacity. Like most M-11s it has a collapsible stock that extends from the butt of the weapon, a selector switch to fire either in semi or full-auto, uses the open bolt method of operation & the end of the barrel is threaded to accept a silencer or other barrel accessory. Compared to other M-11s the “overstamp” guns are generally of a higher quality.

The RPB “overstamp” M-11 is unique because it is a “transitional” gun and may cost more then other M-11s because of its collector value.

The RPB M11-A1 is the first M-11 produced by RPB that did not use frames left over from M.A.C. so they do not have any markings in relation to M.A.C.

The RPB M-11A1 is chambered in .380 ACP & uses steel magazines in either 16 or 32 round capacities. Like most M-11s it has a collapsible stock that extends from the butt of the weapon, a selector switch to fire either in semi or full-auto, uses the open bolt method of operation & the end of the barrel is threaded to accept a silencer or other barrel accessory. Compared to other M-11s the RPB guns are generally of a higher quality.

The RPB M11-A1 may cost more then other M-11s because of its collector value.

Because of lagging sales, RPB was on the verge of going under from finical problems. In the late 1970s Wayne Daniel purchased a large majority of the companies stock and started to produce semi-auto versions of the M11-A1. By removing the collapsible stock and the ability to fire Full-Auto, the open bolt SM11-A1 became a Title 1 pistol and could be purchased by anyone.

These new semi versions of the M11 sold like hot cakes until the BATF intervened in 1982 because they felt these open bolt semi-auto copies could be converted to Full-Auto to easily. Because of this all open-bolt pistol produced after 1982 are considered Machine Guns and this is why we don’t see semi-auto open bolt guns any more.

Luckily for owners of these semi-auto pistols all guns not modified on or produced before the ruling were grand fathered and not considered machine guns.

Unfortunately this ruling by the BATF hurt RPB financially and brought unwanted legal attention so Wayne Daniel dissolved the company in April 1982.

The RPB SM11-A1 is chambered in .380 ACP & uses steel magazines in either 16 or 32 round capacities. Unlike most M-11s it has no collapsible stock that extends from the butt of the weapon and only fires in semi-auto. It does use the open bolt method of operation & the end of the barrel is threaded to accept a silencer or other barrel accessory. Compared to other M-11s the RPB guns are generally of a higher quality.

The RPB SM11-A1s is rare because they are the last of the legal open-bolt semi-auto pistols. Because of this they command a good deal for a Title 1 pistol on the open market because MAC collectors are always on the look out for them.

When Wayne Daniel dissolved RPB in 1982 he started to produce several M-11 varieties under SWD (Sylvia Williams Daniel, his wifes name, NOT Sylvia and Wayne Daniel) Incorporated a year later. The first of these was a slightly redesigned version of the original M-11 that accepted a new lightweight polymer magazine made from Zytel. Unfortunately Zytel magazines didn’t turn out to be a great idea because these polymer magazines would wear down over time and split. The majority of reliability problems reported were because of the Zytel magazine and not the gun itself.

The SWD M11-A1 is chambered in .380 ACP & uses Zytel magazines in several capacities (usually 32 round). Like most M-11s it has a collapsible stock that extends from the butt of the weapon, a selector switch to fire either in semi or full-auto, uses the open bolt method of operation & the end of the barrel is threaded to accept a silencer or other barrel accessory. The grip on the SWD M11-A1 is a little larger then the other M-11s because of the larger Zytel magazine. Compared to other M-11s the SWD guns are “middle of the road” in terms of quality compared to other versions.

The SWD M11-A1 may cost more then other M-11s because of its collector value.

When Wayne Daniel dissolved RPB in 1982 he started to produce several M-11 varieties under SWD (Sylvia Williams Daniel, his wifes name, NOT Sylvia and Wayne Daniel) Incorporated a year later. At the time the 9MM LUGER cartridge was becoming increasing popular in the United States so an attempt was made to produce a M-11 in 9MM LUGER. This wasn’t the first time this was tried. Past companies that produced M-11s all experimented with the M-11 in 9MM LUGER, but like all past experiments, the small frame M-11 could not take the beating from the 9MM LUGER round and guns would basically “beat” them selves apart.

Mr. Daniel found a solution to this problem by increasing the overall length of the rear of M-11 by a few inches giving more room for the bolt to recoil and room for a longer recoil spring that could effectively absorb the 9MM LUGER’s energy. It also accepted the new lightweight polymer Zytel magazine. Unfortunately Zytel magazines didn’t turn out to be a great idea because these polymer magazines would wear down over time and split. The majority of reliability problems reported were because of the Zytel magazine and not the gun itself.

This new version was called the M-11/NINE and became the most numerous version of the M-11 family of weapons.

The SWD M-11/NINE is chambered in 9MM LUGER & uses Zytel magazines in several capacities (usually 32 round). Like most M-11s it has a collapsible stock that extends from the butt of the weapon, a selector switch to fire either in semi or full-auto, uses the open bolt method of operation & the end of the barrel is threaded to accept a silencer or other barrel accessory. Since the gun is chambered in 9MM LUGER the receiver was lengthened at the rear, making this the largest of all M-11s. Compared to other M-11s, some of the M-11/NINEs are on the “lower end” in terms of quality compared to other versions because they were mass-produced and not much was spent on quality control.

One of the best features about the M-11/NINE is that there are so many aftermarket uppers & accessories. These aftermarket uppers & accessories have brought new life to many of these guns because you are no longer limited by the M-11s design faults. A common modification made to the M-11/NINE is a STEN magazine conversion, which allows the gun to use cheap all metal STEN magazines that aren’t prone to failure like the Zytels.

Since the M-11/NINE was the most numerous version of the M-11 produced it is the least expensive.

When the BATF ruled that open-bolt pistols could no longer be produced, RPB’s successful semi-auto line was ruined. In an attempt to recapture the semi-auto market Wayne Daniel developed a closed bolt BATF approved version of the M-11/NINE & M11-A1 for SWD. The new closed bolt design had a major draw back in that its operation produced a painful condition known as “trigger slap”. “Trigger Slap” occurs when the gun resets the trigger and transfers this force into the shooters finger. This can be painful and is usually resolved on M-11s by encompassing the trigger in a piece of rubber hose.

These new closed bolt versions of the M-11/NINE also used the new lightweight polymer Zytel magazines. Unfortunately Zytel magazines didn’t turn out to be a great idea because these polymer magazines would wear down over time and split. The majority of reliability problems reported were because of the Zytel magazine and not the gun itself.

The SWD SM-11/NINE is chambered in 9MM LUGER & uses Zytel magazines in several capacities (usually 32 round). Unlike most M-11s, it does not have a collapsible stock that extends from the butt of the weapon, nor the ability to fire full-auto. It also uses a closed bolt method of operation instead of firing from the “open bolt”. The end of the barrel is threaded to accept a silencer or other barrel accessory. Since the gun is chambered in 9MM LUGER the receiver was lengthened at the rear the gun is larger then most M-11s. Compared to other M-11s, some of the SM-11/NINEs are on the “lower end” in terms of quality compared to other versions because they were mass-produced and not much was spent on quality control.

NOTE: A small run of SWD SM-11/NINE pistols that accepted STEN magazines occurred but there are not to many of these out there.

Since the SWD SM-11/NINE incorporates several of the “evil features” its full-auto brethren has, it is sought after more so then later produced “castrated models”.

When the BATF ruled that open-bolt pistols could no longer be produced, RPB’s successful semi-auto line was ruined. In an attempt to recapture the semi-auto market Wayne Daniel developed a closed bolt BATF approved version of the M-11/NINE & M11-A1 for SWD. The new closed bolt design had a major draw back in that its operation produced a painful condition known as “trigger slap”. “Trigger Slap” occurs when the gun resets the trigger and transfers this force into the shooters finger. This can be painful and is usually resolved on M-11s by encompassing the trigger in a piece of rubber hose.

This new closed bolt versions of the M11-A1 was named the M12/380 in an attempt to distant it self from the newer M-11/NINE to avoid confusion.

The SWD SM-12/380 is chambered in .380 ACP & uses steel magazines in several capacities (usually 32 rounds). Unlike most M-11s, it does not have a collapsible stock that extends from the butt of the weapon, nor the ability to fire full-auto. It also uses a closed bolt method of operation instead of firing from the “open bolt”. The end of the barrel is threaded to accept a silencer or other barrel accessory. Compared to other M-11s, some of the SM-12/380s are on the “lower end” in terms of quality compared to other versions because they were mass-produced and not much was spent on quality control.

Since the SWD SM-12/380 incorporates several of the “evil features” its full-auto brethren has it is sought after more so then later produced “castrated models”.

The TM-11/NINE is the carbine version of the PM-11/NINE dressed up to look like a Thompson. The TM-11/NINE is basically a PM-11/NINE with a 16-inch barrel and a butt stock allowing it to qualify as a rifle.

The TM-11/NINE is officially a rifle and can be purchased by shooters who cannot own a pistol because they don’t own a pistol permit (some places require this) or don’t meet the age requirement.

The TM-11/NINE is different from the CM-11/NINE because it has a finned barrel with a forward grip stock that resembles the Thompson submachine gun.

The TM-11/NINE uses the same closed bolt that the SM-11/NINE used and shares one of its flaws. This flaw was that its operation produced a painful condition known as “trigger slap”. “Trigger Slap” occurs when the gun resets the trigger and transfers this force into the shooters finger. This can be painful and is usually resolved on M-11s by encompassing the trigger in a piece of rubber hose.

The TM-11/NINE also uses the new lightweight polymer Zytel magazines. Unfortunately Zytel magazines didn’t turn out to be a great idea because these polymer magazines would wear down over time and split. The majority of reliability problems reported were because of the Zytel magazine and not the gun itself.

The TM-11/NINE is chambered in 9MM LUGER & uses Zytel magazines in several capacities (usually 10 round). Unlike most M-11s, it has a fixed stock that extends from the butt of the weapon and a finned 16-inch barrel with a Thompson style front grip. It does not have the ability to fire-auto and makes use of the closed bolt method of operation instead of firing from the “open bolt”. The end of the barrel is not threaded and the magazine latch system has been replaced with the notorious “ball catch”. Since the gun is chambered in 9MM LUGER the receiver was lengthened at the rear, making this the largest of all M-11s. Compared to other M-11s, some of the TM-11/NINEs are on the “lower end” in terms of quality compared to other versions because they were mass-produced and not much was spent on quality control.

Also one thing to mention is that sometimes people try to pass off a TM-11/NINE as a pistol or “pre-ban” gun. If the gun says “TM” it is the carbine version and was produced as a rifle and cannot be converted into a pistol (unless you do the paperwork). It is also not a “pre-ban” gun because they were all produced during the AW ban era. It doesn’t matter much now any ways, but some people try to “gouge” the price by claiming it is some that it is not. It is possible to get rid of the “ball catch” magazine problem by purchasing an old style lever catch and replacing it your self.

Since the TM-11/NINE was “castrated” to confirm with the AW ban it is not as popular as some of the earlier or current produced M-11s.

With the sunset of the AW ban in 2004 semi-auto versions of the M-11 could once be produced with some of the “evil features” that were previously banned.

Master Piece Arms has taken this one step further and not only makes a SM-11/NINE type of M-11 with the “evil features”, but has also improved the design.

MPA has all but eliminated the trigger slap and other quality control issue other semi-auto M-11s were known for. They even replaced the Zytel magazine with the reliable STEN magazine that most SWD M-11/NINE owners had switched to long ago.

MPA offers a number of different versions of the MPA-30 with different uppers and configurations (far to many to be listed here). Surprisingly the MPA-30 is distributed by the "new" RPB.

The MPA-30 is chambered in 9MM LUGER & uses STEN magazines in several capacities (usually 32 round). Unlike most M-11s, it does not have a collapsible stock that extends from the butt of the weapon, nor the ability to fire full-auto. It also uses a closed bolt method of operation instead of firing from the “open bolt”. The end of the barrel is threaded to accept a silencer or other barrel accessory. Since the gun is chambered in 9MM LUGER the receiver was lengthened at the rear producing a gun that is larger then most M-11s. Compared to other M-11s, MPA-30 is of high quality compared to other semi-auto versions of the M-11.

Since the MPA-30 incorporates several of the “evil features” its full-auto brethren has, and can be purchased in several configurations, it is sought after more so then AW ban “castrated models”.

Much later, in 2014, a company called and CFT LLC (Cobray Firearms of Tennessee), run by Sylvia Daniel's son Richard Shane Arrington, started making M11/9 semi auto guns.