Effectively Firing a Magazine Fed M249 SAW

Running a M249 with magazine fed ammunition can be reliable if done properly. If done incorrectly, it can cause breakage of the magazine and stoppages inside the gun.

The FN M249 Squad Automatic Weapon (SAW) can be described as “not reliable, finicky, trash”. This however is only due to improper maintenance and operation. Part of that operation involves feeding the M249 by magazine instead of belted ammunition.


Knowing how to use magazines properly within a M249 is important due to this being your last resort for ammunition. The belted ammunition is out and you only have the rounds on your chest or belt in your magazine pouches. This being your last resort or needing to be a very quick reload, you also want to ensure that you are doing this effectively because it is possible to harm the magazine and cause a malfunction in the 249.

The Army -10 Operator Manual States this,


Seat the magazine with the bolt forward. Leaving the bolt forward/closed will keep you from over inserting the magazine. If you do over insert the magazine with the bolt to the rear, the moment you fire and that bolt goes forward it can shear off the magazine lips. Causing both a locked up gun and unusable magazine.

Also, when inserting the magazine, don’t jam it into the magazine well. Simply insert the magazine into the well and push until you hear a click, then give a tug to ensure seating.

P.S. Sometimes when clearing out the 5 points of inspection (one of them being the magazine well) your glove can get stuck inside the well. Don’t panic, simply hit the magazine release and pull it out.

Type of Magazine

Seeing M249’s be fed by both GI magazines and PMAG’s, PMAG’s are the better option.

GI magazines are not reliable inside M249s and have shown that they simply don’t have enough spring power, so to say, to keep up with the higher rate of cycling compared to an AR-15. You can configure the magazines to function a bit better by taking another spring from another GI magazine and stacking them together. Stacking meaning doubling together side by side, not stacking on top of each other. This can give the spring more strength.

This photo is just for reference of how to stack the springs if you were to reconfigure your GI magazines to run in the SAW. I am not saying to use an Enhanced Performance Magazine spring with a Brownells GI mag spring, but you can experiment with it how you’d like.

PMAG’s run inside of the M249 like butter. This past week it was seen that out of ten M249’s on the line and over 30 iterations of firing each, not one M249 had a magazine induced malfunction. Magpul does test their PMAG’s inside M249’s to ensure proper operation.

Fun Fact: Magpul D60’s also run very smooth inside a SAW..

Anna Martinez
Anna is a Federal Weapons Gunsmith with 8 years of previous experience within the US Army Ordnance Corps (91F). She has taken multiple armorer and weapons proficiency classes to include FN, Knights Armament, and Small Arms Weapons Expert course. She also writes for American Gunsmith, AR Build Junkie, and is active in Precision Rifle sports around the nation.