A quality upper that has been faced and has the barrel bedded will produce astonishing results.
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A quality upper that has been faced and has the barrel bedded will produce astonishing results.
Proper Planing Prevents Piss Poor Performance.......
Can you expand on this? Given the same alloy, say 7075, and same final dimensions between a forged and a billet upper, what makes the forged example stiffer/stronger?
I've been trying to wrap my head around this as I've seen a few here post the same. I'm just not seeing it unless I don't understand how a forged upper is made.
I thought forgings were stiffer due to the stresses, but billet was more precise(or maybe uniform) and usually thicker for added rigidity. Is this wrong? I'd like to know so I can explain if asked and actually have an idea of what I'm talking about.
Forged receivers are usually stiffer, ounce for ounce. This is due to the metal grain of the forging following the shape of the part. The grain of the billet is just straight & parallel.
The simpler shape of the billet block makes it easier to index to the machine tool before machining and is easier to make jigs for mass production.
Billet receivers are made thicker and heavier to achieve the same stiffness as a forged receiver
The forged VLTOR MUR is designed to be stiffer than a standard forged upper and is only about an ounce or so heavier
Last edited by MistWolf; 05-11-15 at 07:39.
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Usually, billet receivers are heavier because forged receivers have thinner and more constant web sections and tend to follow the internal contours more closely, thus has less excess material. Billets are limited by how much time they feel like spending machining, they could machine an exact duplicate of a forging*, but that is time consuming...
Stiffness is based on the materials modulus of elasticity and the geometry of the part, grain structure is a very minor player in stiffness. Billet receivers are often made from 6061-T6 with a ME of 10,000 ksi, a forging from 7075 has a slightly higher ME of 10,400 ksi.
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* That's how the forging die was made, after all.
Last edited by lysander; 05-11-15 at 09:10.
Sleeving uppers.........![]()
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It was a reasonable question, especially coming from a benchrest context where sleeving a receiver (but on the outside) for rigidity was once common (might still be but I wouldn't know any more).
I had no idea this question could elicit these sort of responses.
FWIW - post forging solution treating a part will undo any grain alignment gained during the forging process. And it would need to be cold forged anyway. I don't believe these parts are cold forged.
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