NDGlock
06-12-2006, 14:34
I found the source of the rumor going around of vertical foregrips causing torque, which in turn, caused bolt-locking lugs to break.
It was in the June, 2006 Shooting Illustrated magazine in the section where readers may query them at: shootingillustrated@nrahq.org.
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“ M4 Overload
QUESTION:
I have heard a significant number of M$ Carbines being used by our troops in Iraq and Afghanistan have been breaking their bolt-locking lugs. Why is this happening? The M4 is based on the M16 system and has been around for decades without this problem.
- Jan Plaster, via email
ANSWER:
Unfortunately, many M4 Carbines have experienced broken locking lugs in recent action overseas. Initially it was thought to be a manufacturing problem, but further investigation has found the real culprit.
The M4 has been fielded to many units with an integral-rail-handguard system that allows the mounting of a wide variety of accessories like laser designators, flashlights, red-dot sights and vertical fore-grips. Some have turned a light, handy weapon into a veritable Christmas tree of accessories, with the accompanying bulk and weight. All of this extra weight can cause the barrel and barrel extension, into which the bolt locks, to droop in the receiver slightly.
A particular offender is the popular vertical fore-grip. Shooters typically pull this grip solidly to the rear with substantial leverage that loads the barrel and barrel extension in the receiver even more. As the barrel and barrel extension yield to this pressure, the locking lug seats in the barrel extension are no longer vertical. When the locking lugs go into battery, only the top lugs are engaging. The bottom lugs are not touching the lug seats at all. Even the top lugs are only engaging at the end of the lug. Those lugs are receiving all the rearward thrust on the bolt, and that thrust is well beyond their design and capability. The result is the lugs are failing. “
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Here are some source links to this topic:
http://www.nrapublications.org/sh.%20illustrated/index.asp
http://www.glocktalk.com/showthread.php?s=&threadid=540857
It was in the June, 2006 Shooting Illustrated magazine in the section where readers may query them at: shootingillustrated@nrahq.org.
----------------------------
“ M4 Overload
QUESTION:
I have heard a significant number of M$ Carbines being used by our troops in Iraq and Afghanistan have been breaking their bolt-locking lugs. Why is this happening? The M4 is based on the M16 system and has been around for decades without this problem.
- Jan Plaster, via email
ANSWER:
Unfortunately, many M4 Carbines have experienced broken locking lugs in recent action overseas. Initially it was thought to be a manufacturing problem, but further investigation has found the real culprit.
The M4 has been fielded to many units with an integral-rail-handguard system that allows the mounting of a wide variety of accessories like laser designators, flashlights, red-dot sights and vertical fore-grips. Some have turned a light, handy weapon into a veritable Christmas tree of accessories, with the accompanying bulk and weight. All of this extra weight can cause the barrel and barrel extension, into which the bolt locks, to droop in the receiver slightly.
A particular offender is the popular vertical fore-grip. Shooters typically pull this grip solidly to the rear with substantial leverage that loads the barrel and barrel extension in the receiver even more. As the barrel and barrel extension yield to this pressure, the locking lug seats in the barrel extension are no longer vertical. When the locking lugs go into battery, only the top lugs are engaging. The bottom lugs are not touching the lug seats at all. Even the top lugs are only engaging at the end of the lug. Those lugs are receiving all the rearward thrust on the bolt, and that thrust is well beyond their design and capability. The result is the lugs are failing. “
-----------------
Here are some source links to this topic:
http://www.nrapublications.org/sh.%20illustrated/index.asp
http://www.glocktalk.com/showthread.php?s=&threadid=540857
