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Will a Semi-Auto Safety Slide Function in your Full-Auto MAC Machine Gun?

Here is a common problem we get from customers:  “My MAC Machine Gun will only run with irregular burst fire regardless of the position of the selector lever.”  Often times when our customers have this problem, prior to coming to us for help they will throw parts at the problem such as a new bolt, new springs, new extractor, and the list will sometimes go on and on.  Then after researching the issue further the customer will discover that the Safety Slide is what is causing the problem.  The cheapest and most prevalent source for a new safety slide is an aluminum safety slide designed for the Semi-Auto MACs.  See picture below:

So this brings us to the title question.  Will a Semi-Auto Safety Slide function in your Full-Auto MAC Machine Gun?  This a good question and the short answer is yes but not for long.  OK, so that’s not a good enough answer.  Here’s the long answer and explanation.  

The original style safety slide was made of cast aluminum.  Now-a-days, most of the safety slides on the market are also cast aluminum.  Aluminum is a soft metal and when under heavy stress it will wear out pretty quickly.  In the case of an aluminum safety slide, when in use, it is constantly being compressed by the sear which keeps the sear from dropping too far and thus allowing the machine gun to shoot full auto without the trip getting in the way of the disconnector.  However, with each round, that steel sear wears away at the aluminum safety slide and after a certain point, the safety slide is worn away too far and the resulting malfunction is irregular burst fire. 

Sometimes the customer will purchase a safety slide designed for a semi-auto MAC because these are the cheapest and easiest to come by.  This option will work in the short run.  Go back to the picture listed above; look at the semi-auto safety slide furthest to the right.  See where the arrow is pointing to the worn area?  The semi-auto safety slide comes new with that cut out area.   So, not only is the area that holds the trip in place cut away when it’s new, but it’s also aluminum so it’s soft and will wear quickly. 

Now look at that same area on the full-auto safety slide just to the left.  As you can see, it’s not cut out in any way.  This allows for more material to hold the sear from dropping and thus allowing for full-auto fire.  This part will last much longer than the semi-auto safety because it will take more time for the sear to wear away at the aluminum.  This is what we call an actual repair, not just a temporary fix.

Lastly, look at the two safeties on the left.  These are designed and manufactured by us, Practical Solutions, as an improvement to the original design.  Not only do our safety slides have even more surface area to stop the sear travel than the original, but they are also made of steel.  Steel on steel will last much much longer than steel on aluminum. 

If you are having issues like these with your MAC, you can buy one of our safety slides or if you have questions, please call us at:  410-404-0320 or email us at:

Happy Shooting!

Key words:  MAC Mac-10, M10, M10/9, M10/45, Cobray®, Ingram, Military Armament Corp., Jersey Arms Works, JAWS, Hatton Industries, Marshall Arms, MPA, Masterpiece Arms, M11, MAC-11, M11/9, M11A1, M11-380, Machine Gun, SMG, Repair, Practical Solutions, SWD, RPB, Lage, Uzi, Grease gun, Zytel