Feature Article, January 2001

This month's article is by William D. Ehringer, Ph.D.  It is being reprinted here with permission from the author.

A MAC History Lesson

By William D. Ehringer

A Comparison Of The Military Armament Corporation Model 10/9 mm (MAC-10/9) And The Sylvia And Wayne Daniels M11 (SWD M11/9) and other MAC-type weapons.

When Gordon B. Ingram first designed his M10 in 9 mm and .45ACP at his Powder Springs Georgia plant, little did he know that this design would be one that would captivate a number of different types of machine gun enthusiasts.  His M10, in the early 1970s, embodied the spirit of making things smaller, more compact, and less expensive.  He also believed in the philosophy that the fewer the working parts, the less that things can break. His theories are now axioms, as the MAC has become almost notoriously known as the most reliable sub-machine gun ever built. However, because his company and others produced a number of clones of his original weapon, a number of different questions have evolved over models and design features.  The most common question (which is really a mistake) is what is the difference between a MAC-10 and a MAC-11 in 9 mm.

For those of you who are into MACs, you know that the MAC-11 is the .380 version of the gun (Table 1).  This question is usually meant to be, "What is the difference between a MAC-10/9 and a SWD M11/9?"  Since I currently own examples of these weapons, I took the time to write down the differences and do a little research on the history and development of the guns and the companies that built them.  In no way am I claiming that this is an all-inclusive list of all the information on MACs. That topic would be better dealt with in a comprehensive book on this subject.  Rather, this short narrative is intended to give the MAC enthusiast a feel for the differences and similarities between the two most popular transferable SMGs ever built.
 

Table 1.  The different models of SMG and open bolt MAC-type guns produced by various manufactures.  This table is by no means intended to be  a comprehensive review of all of the manufacturers and models.  

There are seven distinguishing differences between the SWD M11/9 and the MAC-10/9, and they are as follows:

1. The SWD M11/9 is made of a thinner gauge of sheet metal compared to the MAC-10/9.  The big reason for the difference was not so much the cost but was the weight.  While the MAC-10 is a light weapon, the SWD M11/9 is even lighter.  My feeling is that this makes the SWD M11/9 easier to conceal, and is especially true for its .380 cousin.  In fact, discretionary briefcases were made for these two guns, which allows the operator to fire the weapon from inside of the briefcase without removing the weapon.  The thinner gauge of metal on the SWD M11/9 has not proven itself a disadvantage as far as durability goes, at least in my case, as I have put thousands of rounds in my SWD M11/9 with no appreciable signs of wear or stress.

2. The SWD M11/9 uses a different cocking knob (flat round knob) than the MAC-10/9 (smaller around, but taller). The cocking knob on the MAC-10/9 also acts as a safety, because turning it 90 degrees will lock the bolt in the forward position. The MAC-10/9 knob is also slotted on the top, so that you can actually aim the gun using the peep sight. Sighting using the SWD M11/9 is made near impossible because the cocking knob interferes with sighting.  Furthermore, the original SWD M11/9 cocking knob is not ergonomically designed as only one finger can fit on the knob for cocking the guns near 20-25 lb bolt pull.

3. The SWD M11/9 uses a Zytel or steel magazine whereas the MAC uses steel mags only.  The Zytel mags have had mixed reviews as far as reliability goes.  The major problem with the zytel mags was that the feed lips would bend or break, causing reliability problems.  The other major problem with the Zytel mags was that the seam along the back of the mag would split after being filled to capacity.  Fortunately, there are a number of solutions to this problem.   Tactical Innovations sells a Sten magazine well conversion kit that is easily installed on the SWD M11/9 allowing the use of cheap, reliable Sten magazines.  The MAC-10/9 uses a proprietary steel magazine, (which are becoming scarce...read expensive), but this mag was less susceptible to failures than the Zytel magThe MAC-10/45 uses modified M3 Grease gun magazines.  These mags are modified to fit the MAC-10/45 by shaving 1/16" of steel off of the rear of the magazine (for the mag catch) and 1/16" off the two locking tangs
   on the side of the magazine. The SWD M11A1 in .380 and the MAC-11 in .380 are the guns which cause
   the most confusion in regards to magazines.  The SWD M11A1, which is a shortened M11/9, uses the same magazines as the M11/9 except the feed lips have been heated and bent to accommodate the diminutive .380round. The MAC-11 uses a smaller steel magazine which are rare and often expensive.

4. The SWD M11/9 bolt is smaller, and instead of having a fixed firing pin milled into the bolt face (ala the MAC-10/9), it has a firing pin that is pinned in place.  Numerous other design differences exist between the SWD M11/9 bolt and the MAC-10/9 bolt and include: Dimensional differences, presence of a front detent for the MAC-10/9 cocking  knob, slight weight difference, and overall length difference of the entire bolt, recoil rod and ejector rod assembly.  The SWD M11/9 bolt is the same exact bolt used in the closed bolt semi-auto guns, withthe exception that the SMG bolt's firing pin is not slotted, and lacks the firing pin spring.  One final note, since the firing pin on the SWD M11/9 is nothing more than a piece of sheet metal, owners of these guns should buy an extra firing pin as a spare.

5. The upper of the SWD M11/9 is also smaller in diameter (1" square I.D.) compared to the much larger MAC-10/9 which is about 1.5" square.  While the SWD is smaller and more flat, it is also slightly longer (about 2") than the MAC-10.  My guess was that this dimensional difference was done to compensate for the lack of weight in the 9 mm bolt, by giving it a slightly longer cycling distance.  The factory cyclic rate of both guns is still very high, in the 1100-1200 rpm range, which means that a 30 rnd mag can be emptied in about 1.5 seconds by either gun.  My experience is that the MAC is a tad bit slower than the SWD, but for all intents and purposes, they are both fast cyclic rate guns.

6. SWD M11/9s are also more prevalent, according to Wayne Daniels, SWD made about 17,000 of the M11/9 smg's, 3,800 M11A1 smg's in .380, and 500,000 semi-auto M11/9's.   In contrast, the number of original Powder Springs MAC-10/9s is much smaller, and even more rare is the MAC-11/.380. While other manufacturers made copies of the MAC-10 (see table 1), its collective numbers still do not rival the SWD M11/9.Recently, JLM and Sons purchased nearly all of the remaining inventory of SWD M11/9s and SWD M11A1s.

7. SWD M11/9 is about half the cost of a MAC-10.  Believe it or not, the MAC is becoming a collector's item.  I know, when you bought your MAC-10 in 1975 you paid $125, but guess what, the gun is now worth in excess of $800.  And because the supply is fixed and the demand continues to increase, the value of the MACs only continues to rise. To a lesser extent, the same goes for the SWD M11/9.  In fact, in March of 1998, Mountain Accessory Corporation raised the price of the SWD M11/9 by $100, suggesting that the supply of this once very abundant SMG was dwindling.
   

The above seven differences are certainly not inclusive of all MAC-10/9s as a number of other companies also made the MAC.  I have tabulated some of the differences below and in Table 1 on the manufacturers and lineage of the MAC-10.

Military Armament Corporation (MAC), based in Powder Springs Georgia from 1970-1976 was the first company to commercially produce the MAC Model 10 (MAC-10).This is the company started  by Gordon Ingram that designed and built the first MAC (now you know where the name came from).  MAC marketed a number of different weapons, but the MAC-10 (chambered in 9 mm and later in.45 ACP) and the high cyclic rate (approx. 1600 rpm) MAC-11 (chambered in .380) were its mainstays. MAC declared bankruptcy in 1976 and went out of business.  A number of factors led to their demise, but the big reason was that little or no military interest in the MAC was generated.  MAC sold its tooling and assets (registered and unregistered frames, and parts) to another Georgia-based company called RPB in 1977.

MAC-10 in .45 ACP,  Powder Springs/RPB double stamp gun

RPB (which has been rumored to stand for Rape, Plunder, and Burn) made the MAC in the same calibers as did the Powder Springs Plant, but in some collectors eyes the manufacturing was not on par with the original MAC. Nearly all of the machine guns that came from RPB were either frame flats, frames or completed guns which were bought from MAC in the auction. Because the machine gun market at that time was not as popular as it is today, RPB came up with a new marketing strategy, which was to offer the MAC-10 as a Title I weapon (a semi-automatic) creating an Open Bolt semi-automatic firearm. BATF stepped in mid-1982 and halted the manufacture of open bolt semi's because they were easily convertible to full-auto. About a year later, RPB went out of business.

SWD Incorporated.  In 1983, Wayne Daniels, a former principal at RPB Industries, started his own company.  He modified the existing MAC design and created the SWD (Sylvia and Wayne Daniels) M11/9. The gun was  MASS-PRODUCED, and that is the reason that so many are still offered for sale NIB. When the MG ban went through in 1986, SWD sold the rights (or became part of) Cobray. Cobray started marketing the closed bolt design Cobray M11/9. This semi-auto uses the exact same MG receiver as did the SWD M11/9, with only a few exceptions (selector switch not drilled, sear pin, and re-enforcing plates absent). After the Assault Weapons Ban in 1994, the Cobray M11/9 could no longer be made, so Cobray re-marketed the gun with a non-threaded barrel and a mag release as the PM-11/9.

Other Manufacturers

1. MAC, Stephenville, TX-James Leatherwood took the MAC design from the Powder Springs plant and redesigned the gun to be "better".  In short, Leatherwood redesigned the trigger mechanism, the safety, and the stock.  Some of these improvements were viewed as "improvements" others were viewed as "disappointments".  The guns built by Leatherwood were also tack welded rather than TIG welded.  This turned out to be the biggest disappointment as the "Texas MAC" has a reputation of shaking their tack welds loose and in some cases injuring the shooter.  Many of the Texas MAC frames (I have heard in excess of 1000) were purchased by Wayne Daniels when Leatherwood operation folded.  These "Texas MACs" frames were built-up using RPB and Cobray parts and most importantly, they were TIG welded. The SWD Texas MACs use a SWD magazine housing, SWD grip, SWD 9mm barrel, and most importantly the SWD Zytel mags.

2. Jersey Arms-this company built M10/9s and M10/45s before folding. These guns were built using essentially the same designs and principals as the PS and RPB guns and were made by Hatton Industries in Indian Mills, New Jersey.

Suppressors

Now as far as original suppressors go, two general types were built: a single-stage suppressor that used Nomex wipes and a two-stage suppressor that was wipeless in design. The two-stage suppressor was the original can made for the MAC.  The single stage suppressor came along afterwards and was the one hated by its owners, and later by the ATF.  The big reason for this hatred was that for the suppressor to achieve decent sound suppression, the internal wipes had to be replaced after only a couple hundred rounds.   This is when Gun Show vendors started selling replacement Nomex "wipe kits."  Problem was, that the same vendor would also sell the tubes the wipes fit in, and those individuals who made a suppressor in violation of the NFA ruined it for us all.  This is when ATF ruled that any suppressor part was indeed a suppressor and had to be either registered or in the possession of a Class 2 manufacturer. Well as you can imagine, this shut-down the "spare suppressor parts business" and owners of these cans had a "limited life suppressor."

Two stage suppressor, with internals and a 
homemade tool for removing the encapsulator

On the other hand, the two-stage suppressor can be easily disassembled and cleaned. It is easily distinguishable from its single stage cousin, because it has a larger tube screwed into a smaller tube, whereas the single stage is just a straight tube.  Inside of the first stage of the suppressor (which cannot be readily disassembled) are shoestring eyelet's.  The second stage contains an inverted baffle cone, then two spiral-type baffles held in place by an encapsulator. Threaded into the end of the suppressor is the only "disposable part" which is a rubber or wax-type grommet end cap. Going price for a single-stage suppressor is about $125-200, while the two-stage suppressor is in the $200-300 range (depending upon manufacturer and condition). RPB and MAC made two-stage cans, while I believe SWD and Cobray made the single stage cans.

Disassembly instructions

The MAC is a very simple gun to strip.  I am going to assume you have a full-auto MAC, and since I own only PS, RPB and SWD guns, I am going to give you the necessary information to strip these SMGs.  The Texas MACs are a little different so some steps may need to be fine-tuned in order to get them to work.

First remove the magazine from the gun and make sure it is unloaded.  Cock the bolt back and make sure there are no rounds in the chamber (actually this is theoretically impossible in an open bolt gun as the bolt resting in the battery position should ignite the round, but always check and be safe). Remove the front pin (two pin design may require a screwdriver to push the small pin latch off the outer big pin).  Remove the upper receiver from the lower receiver by pulling forward.  Remove the bolt from the upper receiver by moving the bolt rearward until the cocking knob is centered in the large hole at the rear of the cocking knob race.  Pull up on the cocking knob to remove.  The bolt can then be removed from the upper by sliding it out the back.

(At this point, you are field stripped and ready to clean the lower and upper components.  However, if you want to strip it to parts read on)

Push in on the stock latch button and simultaneously pull the stock rearward and out of the receiver.  Using a small screwdriver, push down on the stock latch plunger located under the most rearward pin and push this pin out of the receiver.  The plunger, spring, and latch can now be removed. The stock latch is welded to the frame and is not removable.

On the grip, remove the grip screw and grip.  Push the magazine catch pin through its hole and remove the magazine catch and spring.

 

In the trigger group.  Pull up on the selector spring (long wire that runs along the left side of the receiver) and pull the selector switch out of its hole.  This may take some gentle nudging and holding down of parts.  Once the selector is removed, the disconnect (thin piece of sheet metal nearest to the selector switch hole) is free and is removed.  Also the sear is now free and is removed.  The trigger is held in place by a trigger pin.  Gently tap on this pin to remove it (some pins are directional so try this procedure GENTLY on both sides until the pin moves freely; however, all of the SWD, PS, and RPB guns have a trigger pin that removes from the left side).  With the trigger pin removed, the trigger can be removed, and the safety is no longer held in place.  To remove the safety, carefully tap the safety roll pin free from the safety and remove the plastic safety button.  The safety assembly is now free and can be removed (Be careful as the safety has a small spring and detent which can easily be lost).

The bolt strips easily as well.  First compress the bolt on its spring assembly about 1-2" to expose the recoil rod.  At the tip of the rod is a small roll pin.  Tap this roll pin out and carefully remove the spring (Caution: The spring is under a fair amount of force and you should wear eye protection when working on the gun). With the spring removed, the recoil rod/ejector rod assembly can be removed.  The bolt only has one working part: the extractor.  To remove it, carefully drive the extractor retaining pin out of its hole.  I like to use a drift punch that is the same size as the hole, this way the extractor is retained on the punch and I can dictate the "terms" of its removal.  Remove the extractor and extractor spring.

The barrel should be removed only when necessary.  Before you start, spray some Break Free on the threads for the barrel inside of the upper to help loosen it prior to proceeding.  Remove the upper from the gun and remove the bolt.  Place the upper on a soft surface and tap the barrel-retaining pin from the RIGHT SIDE, so that the force of removing the pin acts to loosen the barrel (lefty-loosey).  Place the end of the barrel in a vice that is lined with rubber or thick leather.  Using a large screw driver or metal rod that will fit in the upper receiver forward retaining hole, slowly loosen the UPPER from the barrel (i.e., the barrel remains stationary and the upper is turned).  I have had barrels that were easy to remove and I have had some that I swear were welded in place.  The key is patience and a good vice.

Re-assembly of the MAC is simply a reversal of the above steps.

Conclusion

In short, the choice of either the SWD M11/9 or the MAC-10/9 is an excellent choice as a SMG, especially as a first time NFA weapons purchase.  The biggest complaint about either gun is that they have very high cyclic rates.  This is great when you first get the gun, but after the "fun" of dumping $6-8 down range in 1.5 seconds ends, most owners start seeking more "accurate means."  Problem is, accurate usually spells expensive and thus MAC-10 and SWD M11/9 owners were left with a bullet hose.  However, others and I have developed a means to convert a standard SWD M11/9 SMG into a VERY competitive SMG.  In fact, the Slow-Fire M11/9 has beaten out MP-5s, M16/9s, and other rare and expensive SMGs in competition.  For a complete description of the conversion plans for creating a Slow-Fire M11, see my write-up on James Kitching's Fun Supply Board at: http://www.tecinfo.com/~jayhawk/m11slow.html or alternatively you can read the even more comprehensive write-up on this conversion in a future edition of Small Arms Review.

In my opinion both the SWD M11/9 and the MAC-10/9 are great, inexpensive, easily accessorized, and easy to maintain submachine guns. No matter which one you choose, I can almost guarantee that shooting it will put a smile on your face.
 

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