We work at TACOM FMX and have noticed the adjustable buttstock on M249 machine guns is coming loose from the back plate. This can be fixed by tightening the buttstock.
Here’s what all the parts look like (click on image for larger PDF version).
Fig 4. Lightweight collapsible buttstock disassembly
(click on image above to view and download PDF)
Here’s how to tighten the buttstock:
- On the adjustable buttstock you will have to remove the cheekrest. Loosen the thumbscrew in the cheekrest to take off the cheekrest (Item 3 of Fig 4).
2. To remove the adjustable buttstock, push the retaining detent and adjustment detent in (Items 2 and 6 of Fig 4) and rotate the buttplate assembly counterclockwise. This will hold both detents in and allow you to slide the stock off. But be warned that the adjustment detent and retaining detent are under spring tension. Always secure (by holding in place) the detents when disassembling to prevent parts from becoming projectiles that cause injury or loss of parts.
3. Once the buttstock is removed, the adjustment detent, retaining detent and spring will come out (Items 2, 6 and 7 of Fig 4 above).
Detents and spring
4. Remove the retaining pin and collar by first pushing the pin out of the tube (Item 8 of Fig 4).
Then slide the collar out of the tube (Item 9 of Fig 4).
5. Tighten the buttstock by using a 7/32 Allen wrench on the Allen screw inside of the back plate assembly (Item 1 of Fig 4).
Tighten the buttstock
6. Reverse this procedure to put the buttstock back together.
Instructions are also in WP 0019 of TM 9-1005-201-23&P (Oct 14). This procedure pertains to the M249 machine gun only. Although the M240B machine gun is similar, loose buttstocks are corrected differently.
Fred Fanning II
Ft Leonard Wood, MO
Editor’s note: Thanks for the tips, Fred, Mark and David. Operators, remember to tell your armorer if your M249 machine gun’s buttstock is loose so it can be tightened.