Old School MAC Cans

By Frank Iannamico

During the 1960s–1970s there were very few companies manufacturing suppressors, AKA silencers, in the US. Few/none were making them for the civilian market, which was virtually non-existent at that time. One of the few companies of that era was SIONICS which stood for “Studies in Operational Negation of Insurgency and Counter Subversion.” SIONICS’s business was mainly directed at governments—US and foreign.

SIONICS Incorporated

When Mitch WerBell III began his clandestine weapons business, he set up shop on his property near Powder Springs, Georgia in 1966; in 1967 the company incorporated. Initially, the product line consisted of suppressors for the US M14 and M16 rifles, later adding pistol and submachine gun suppressors. On December 21, 1970, SIONICS officially changed its name to the Military Armament Corporation also known as MAC.

Gordon Ingram firing a suppressed MAC-10 submachine gun. Despite their large size, many like the classic look of the old MAC suppressors on their Model 10. In addition to suppressors made by the Military Armament Corporation, similar models were made by RPB and SWD. There were also copies made by a number of individuals and companies using tubes and components sold by RPB and SWD. One problem with the MAC-type suppressor were their coarse threads, which would loosen while firing. (PHOTO DON THOMAS)

SIONICS Sound Suppressors

Most of the suppressors that SIONICS/MAC designed and sold, used rubber discs called wipes to help suppress the muzzle report. The life expectancy was 200 rounds before the unit’s efficiency deteriorated and the wipes required replacement. A wipe replacement module was available as a separate item. Mitchell WerBell III’s achievements in suppressor design were often regarded as the most significant advancements since Hiram Maxim’s silencers were patented in 1909. Some of WerBell’s best-known suppressors were those made for the MAC submachine guns.

The M10 and M11 suppressors’ rear section had a core that was a simple tube with a series of holes; the area around the core was packed with shoestring eyelets. The front section had a simple baffle followed by two helicals—one right-hand spiral, the other left-hand—designed to slow down the escaping gases. A threaded plate was used to hold the parts and the wipe assembly (consisting of several urethane disks and spacers crimped into a module) in place. A few modern suppressor manufacturers that upgraded the MAC suppressors agree that the original rear section (with the eyelets) is effective. The front section with the helicals was the area in need of improvement. In 1972, the factory price for a MAC suppressor was $57.00. From 1971 to 1973 the Military Armament Corporation produced 1,138 .45-caliber suppressors, 1,659 9mm suppressors and 1,983 .380-caliber suppressors, plus a number of pre-production prototypes.

No Civilian Sales

The SIONICS/Military Armament Corporation’s marketing strategy was to sell their weapons in substantial lots to governments and police agencies. The corporation was not interested in selling the guns piecemeal and discouraged sales to individuals.

Foreign Suppressor Sales Banned

Early in 1974, the United States Department of State placed an embargo on the export of sound suppressors to many third-world countries. In May of 1974, the US suspended all export license applications to “developing” nations involving suppressors and automatic weapons having threaded barrels for suppressors. The US Government ruling severely curtailed the foreign sales of MAC submachine guns.

Model 10 suppressor, a Model 10 briefcase suppressor and a Model 11 suppressor. All used the shoe eyelets and helicals design with replaceable wipes in the endcap.

Sales Suffer

The Military Armament Corporation sold to customers in over 50 foreign countries. Foreign sales nearly dried up completely when the sale of suppressors outside of the United States was banned. The US felt that any weapon that was fitted with a suppressor was an assassin’s tool and didn’t want any US firms offering such weapons overseas. The suppressor was what attracted many buyers to the M10 and M11 weapons; without it, the MACs were just another submachine gun, competing with many more practical designs.

MAC Bankruptcy

During 1974, the management of the Military Armament Corporation made a list of pending litigations and lawsuits. There were 29 named individuals and entities on the list that included numerous tool and part vendors, attorneys and shipping companies. During 1975, the Military Armament Corporation began to default on payments to creditors. In December, the Military Armament Corporation was forced to file for bankruptcy.

Cut away Model 10 suppressor. Many modern suppressor manufacturers agree that the shoestring eyelets in the first stage are quite efficient. However, the efficiency of the right and left helicals of the second stage can be improved by replacing them with modern baffles, which also eliminates the end wipes.

The MAC Auction

In April 1976, the remaining inventory of the Military Armament Corporation was ordered to be auctioned off by a US District Court Bankruptcy Judge. The auction was to commence on June 14, 1976, and continue until completed; the auction lasted for two days. Potential bidders were offered an extensive inventory of suppressors and submachine guns. Material presented at the auction consisted of 2,400 9mm Model 10 submachine guns, 6,400 .45-caliber Model 10 submachine guns, 174 .380-caliber Model 11 submachine guns and 1,925 suppressors of various calibers. There were many suppressor internal parts and tubes, but the ATF would not permit them to be sold. On June 11, 1976, a few days before the auction began, there were a number of submachine guns and suppressors confiscated by the ATF.

RPB Suppressors

After the Military Armament Corporation went out of business, RPB was formed by several former MAC employees. They purchased many parts, guns and suppressors before and during the auction. The original RPB partners manufactured a small number of suppressors; it was only after Wayne Daniel became involved with RPB that the company began to manufacture and market large numbers of suppressors, which were essentially the same designs as those originally sold by the Military Armament Corporation. There were approximately 700 original Military Armament Corporation suppressors of various calibers bought at the auction by Precision Armament (a Wayne Daniel company) and transferred to RPB. In 1979 RPB was selling its suppressors for $199.99 retail.

A Powder Springs Model 10 with a matching serial number suppressor. Matching number suppressors were available from the factory, but over the years, many of the submachine guns were separated from the suppressors, as many thought they were not worth the price of the required transfer tax. However, the old suppressors have recently been rediscovered by nostalgic MAC enthusiasts.

RPB .45-Caliber Suppressors

The RPB two-stage .45-caliber suppressors were nearly identical to those made by MAC, having a large diameter primary tube and a smaller diameter second stage tube. A total of 961 of the two-stage .45-caliber suppressors were made by RPB from October 1977 to October 1982.

RPB .45-Caliber Briefcase Suppressors

The full-size Model 10 submachine gun was not able to fit inside the operational briefcase when fitted with a suppressor. To address this problem, a shortened version of the suppressor was made. The suffix of the short suppressor’s serial numbers was the letter K representing Kurz or short. A total of 11 units were recorded in March 1982.

RPB 9mm Suppressors

In July 1977, RPB began their 9mm two-stage suppressor production. Like their .45-caliber counterparts, the 9mm suppressors had a large diameter primary tube and a smaller diameter second tube. A total of 796 9mm suppressors were made when production ended in 1982.

RPB made 11 9mm “briefcase” suppressors on March 3, 1982, which had a shorter overall length. This was to allow a full-size Model 10 to fit into the operational briefcase with a suppressor attached.

A MAC employee machining suppressor tubes at the factory in Marietta, Georgia. Note the stock piles of tubing on the right. (PHOTO DON THOMAS)

RPB .380-Caliber Suppressors

RPB .380-caliber suppressor production began in October 1977. The RPB .380-caliber suppressors, like their MAC predecessors, were a two-stage design, and like the MACs, the entire length of the tube had roughly the same outside diameter. A total of 797 .380-caliber suppressors were made before production ended in October 1982.

SWD Suppressors

SWD manufactured and sold submachine gun sound suppressors that were the same design as those made previously by both MAC and RPB. The SWD suppressor was available for the Model 10 in 9mm and .45 caliber and the M11/.380 and the SWD’s M11/Nine. The SWD suppressors sold for $140.75 postpaid. SWD made 460 .45-caliber suppressors and 448 9mm suppressors with production ending in August 1988. SWD produced 660 suppressors for the M11/.380 submachine guns from January 1983 until January 1989.

During 1983, SWD announced their new High Efficiency (H.E.) sound suppressor line specifically designed for their recently introduced M11/Nine 9mm submachine gun. The SWD H.E. design had a tube that was the same diameter of 1.75 inches for its entire length of 11.625 inches, unlike the earlier two-stage MAC designs where the primary stage was larger in diameter. Advertised as “quieter” the SWD H.E. suppressor used three high-density copper mesh cylinders, separated by triangular baffles, in place of the SIONICS/MAC spiral-type baffles and eyelets. The High Efficiency suppressor would also thread onto the 9mm Model 10 and was available for $140.75 postpaid. SWD’s 9mm H.E. suppressor production began in June 1983, ending January 1989; during that time 1,409 H.E. suppressors were produced. SWD also sold suppressor internal replacement parts and wipes for all of the MAC suppressor models.

Companies like SWD offered ìreplacementî suppressor parts. Although not advertised together with the internal parts, suppressor tubes were also available. Due to the proliferation of unregistered suppressors, laws were enacted making it illegal to possess spare suppressor parts.

First MAC Suppressor Upgrades

Around 1980, Dr. Phil Dater of Gemtech fame, designed a wipeless end cap called the MAC-END for the MAC-type suppressors. A few years later he offered a complete “enhancement” kit of baffles and spacers to use along with the MAC-END. The ATF ruling that made possession of suppressor parts a felony ended the availability of the enhancement kits. In 1981, Dr. Dater designed the “Superwipe,” which was a 4-inch long tube with a coupler to thread into the existing M10 suppressor, a support for some fiberglass insulation and a wipeless end cap. The Superwipe would simply screw in in place of the existing end cap. Subjectively, it was a further improvement, but the suppressor was overly long. Drawings were submitted to the Tech Branch of the BATF. The response was that it could be adapted to a firearm by itself, and because of its design, it would be a suppressor, thus the production of the Superwipe was denied.

While Ingram’s Model 10 and 11 submachine guns came from the factory suppressor-ready, the weapons have been largely ignored by modern suppressor manufacturers. One of the first non-MAC factory suppressors was designed by Phil Dater and Lynn McWilliams during 1986. Designated as the M10A3 suppressor, they were manufactured by AWC of Houston, Texas. Basically, they followed the original MAC design but improved it by replacing the eyelets in the primary tube with steel mesh and the helicals in the secondary tube with stainless steel baffles. The module containing the rubber wipes was replaced by a wipeless MAC-END. The M10A3 was approximately 2-inches longer than the original MAC cans. The M10A3 was available in 9mm or .45 caliber. There was also a .380-caliber model designated as the M11A3. However, the problem of the suppressor coming loose because of the coarse barrel threads remained. The M10A3 suppressor was superseded by the legendary MK9 suppressor configured for the MACs.

Updating to Modern Baffles

Suppressors were a popular option on the MAC submachine guns. The 1970s-era suppressors are now quite dated and have been replaced by smaller and lighter wipeless designs. However, many enthusiasts like the “old school” look of the big original MAC suppressors. Often a MAC submachine gun was sold with a serial-number matching suppressor. Many of the matching-number suppressors were separated when a submachine gun was sold to an individual who did not want to pay an additional $200 transfer tax for an outdated suppressor. One drawback to the early MAC cans was their wipes, which only lasted a few hundred rounds before replacement was required to restore the can’s effectiveness. The wipes not only required periodic replacement but affected accuracy. The basic issue was that anything that touched the bullet once it left the rifling would deflect it and open the shot group. While not an issue at a range of 10-15 feet, at 50 or more feet accuracy deteriorated quickly.

Fully aware of the old MAC suppressors’ renewed popularity, modern suppressor manufacturers like Tom Bowers now offer a service to update the old cans by replacing the helicals with modern baffles, eliminating the old wipe system. Bowers, like most of the others who update the old cans, feel that the original eyelets in the first stage work quite well and leave them intact.

Recommend reading: The MAC Man: Gordon B. Ingram and His Submachine Guns, available from Chipotle Publishing, LLC at www.chipotlepublishing.com.

This article first appeared in Small Arms Review V22N8 (October 2018)