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M1/M14 receiver design question

lew

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Howdy,

I've been wonderin' to meself: why does the heel of the receiver- and therefore the bolt's travel- dip downward on the M1 and M14?

Is it to make room for the rear sight assembly? Doesn't seem that way, but I've been wrong once before. Seems like it's an unnecessary wear point, at least for the rear of the bolt.
 

easttex

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I suspect it's because the bolt rides too high to travel straight back like an AR bolt carrier. Hence, it has to project slightly downward, following the contour of the stock grip in order to cycle in/out of battery.

Honestly, until I got a good look at one, I thought the thing just somehow folded out of the way. Now that I have an M1, it makes sense.
 

lew

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Good points. Appears to be a strange design choice, but I'd imagine there's a reason for it. Just spitballin', but I wonder if it has any effect on case ejection.🤔
 

lew

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Just a guess here, but the heel sloping down may help decelerate the bolt after it has cocked the hammer.
I think we're gettin' somewhere with this. The reciprocating mass of the bolt and op rod on an M14 always felt to be on the lighter side to me.
 

Impala_Guy

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I would say its to follow the arc of the hammer somewhat and also distribute the impact force of the bolt against the heel a little bit. Remember on early Garands they lead dip annealed the receiver heels because of cracking issues (which I think were resolved with adjustments in the steel and heat treat)
 

gunshack

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There are a lot of peculiarities about the design of the Garand/M14 that look odd from modern engineering standards, but keep in mind that many of these designs were developed over a long period of time, with lots of trial and error. The bottom of the bolt is machined with 22" radius, which is obviously larger than the radial rotation of the hammer. I believe the "rotation" of the bolt as it cycles is (in part) meant to reliably interface with the hammer, and it probably helps with ejection trajectory.
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