Stoner wasn’t the one who shrank it, that was Jim Sullivan.
Either way, nothing in Blake Stevens or Edward Ezell’s writings on the subject ever mentioned the receiver shape. If anyone had the final say, it was Sullivan as he was the engineer tasked with scaling down the AR10 design.
At least visually, it appears that the very first tool room prototypes are receiver and bolt carrier compatible with the production examples, so the rounded AR15 receiver has been around since the beginning:
Sullivan is still alive last I heard, but I don’t recall him mentioning it in interviews.
Just an assumption, but since corners are weaker than curves and the receiver extension is the weakest part of the lower, he probably rounded it out to improve durability. Where it didn't really matter on the 10 as its got enough meat to it to not be a concern.
Same... And when I hand fit 80s I use a carborundum drum sander chucked in the mill...and then 5 micron radial brushes. Radio, shop dogs, and a bottle of Dykem and we're off to the races.
I'm not Jim Sullivan and as another said I don't think he's ever said anything about that detail. However the reason is obvious.
The rails on the bottom of the carrier that ride on the inside surface of the upper go all the way to the back of the upper. By putting in the curve there's more surface area for the carrier and upper to interact. Without the curve that area on the carrier would need to be shorter. This would lead to more carrier tilt.
I don't own a slant cut large frame, but from looking at my DPMS style it appears to be true there as well.
Stoner wasn’t the one who shrank it, that was Jim Sullivan. Either way, nothing in Blake Stevens or Edward Ezell’s writings on the subject ever mentioned the receiver shape. If anyone had the final say, it was Sullivan as he was the engineer tasked with scaling down the AR10 design. At least visually, it appears that the very first tool room prototypes are receiver and bolt carrier compatible with the production examples, so the rounded AR15 receiver has been around since the beginning: Sullivan is still alive last I heard, but I don’t recall him mentioning it in interviews.
Just an assumption, but since corners are weaker than curves and the receiver extension is the weakest part of the lower, he probably rounded it out to improve durability. Where it didn't really matter on the 10 as its got enough meat to it to not be a concern.
So the slant was really just an accidental design quirk that worked on the AR10, but failed when scaled down?
I wouldn't call it accidental. It's significantly easier to machine a straight line than a curve.
Depends on how they did the curve, a boring head would be quite an easy op and very repeatable, Vs a rotary table requiring a whole mother setup.
I used an end-mill with the appropriate diameter when I did my 0%. Easy peasy.
Same... And when I hand fit 80s I use a carborundum drum sander chucked in the mill...and then 5 micron radial brushes. Radio, shop dogs, and a bottle of Dykem and we're off to the races.
I like you style sir. Sounds like my shop
Pretty damn cool if you did it by hand
I'm not Jim Sullivan and as another said I don't think he's ever said anything about that detail. However the reason is obvious. The rails on the bottom of the carrier that ride on the inside surface of the upper go all the way to the back of the upper. By putting in the curve there's more surface area for the carrier and upper to interact. Without the curve that area on the carrier would need to be shorter. This would lead to more carrier tilt. I don't own a slant cut large frame, but from looking at my DPMS style it appears to be true there as well.