Quote History Quoted:
They were initially fielded with them in the early 60's..the USMC had slotted guards in '64.
Later production had solid. Yours were later production or replaced with solids under a TB advisory.
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This.
First they were walnut (T44E4), which charred and burned, so was quickly replaced with vented fiberglass, probably late in 1960.
Then later they realized mirage was a problem so they went solid. The solid ones are also less fragile.
The vents/slots were eliminated after the drawing date of October 18, 1961. (Probably beginning early 1962.)
Source:
https://www.m14forum.com/threads/m14-original-color-hg.35129/#post-213055You're not likely to have a problem with mirage in only one mag. It depends on environmental conditions, the wind, etc. but you'd need extreme worst case to have obstruction within a single mag.
I use a vented handguard on an M14A1 because it looks cooler.
(It does help cool the barrel a little too.)
M14A1 20 rounds offhand bursts
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