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Originally posted by Rusty....
Swamp! How ya doing buddy?

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triggergard1,

What are the major issues with castings of SAE8620? By the way, what material are Ruger and the others using in these castings, do you know (or anyone else)?

I asked headache the questions because I am interested in hearing what the molecular differences are that he is referring to. Is he referring to casting voids (porosity), or grain structure? If grain structure what is the problem; too coarse, too fine?

You do realize don't you that bar stock is "cast" don't you?

By the way, what are headache's creditials?

ASS_CLOWN

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Rod Rodgers could probably tell you exactly what the composition of Ruger's castings are, since Pine Tree casted MRC's receivers, from what I understand, from the same material.

Grain structure, or what there is of it, is more course in the investment cast process than the others mentioned. Of all the casting processes, MIM seems to be the best, but is limited to somewhat small parts. This however is changing in recent years as the technology continues to improve. The detail and intricacy that is obtainable in the MIM process is probably the most impressive part of the entire process.

I do realize that barstock is casted in a sense, but not like the investment cast process. With that said, barstock is susceptible to voids caused from impurities in the manufacturing process, but is far less likely to occur than an investment casted part. Furthermore, round barstock is even less likely to experience these problems than say square, or rectangular barstock.
Forgings are almost always made from round barstock, so not only do they almost invariably lack the problems of bad grain structure, they are then heated to red hot conditions and formed into their shapes within the die. This eliminates, or at least virtually eliminates any stresses within the material that can be released during the machining processes.
Forgings are a cost cutting item, but unlike casted parts, they don't take away from the quality, quite the opposite in fact.

We've been using forgings in our processes for over 11 years and it has allowed us to make high quality part without all the wasted material that's associated with barstock. The other big benefit is the fact that the barstock that is used for the forging is round, which is much easier to obtain in volume, as well as being less expensive per pound.

Headache will have to be the one to decide whether he lets the cat out of the bag on what he does for a living. All I can tell ya is, we've known him for quite a while, and he has quite the reputation over many years in the firearms industry.

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"The 700 receiver starts as length of standard 1 3/8" diameter bar stock. The metal is AISI-4140 Chrome-molybdenum annealed steel

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Make life simple for yourself: Get a copy of Stuart Otteson's great book, "The Bolt Action", and then you can look up the construction predications of the various major actions for yourself, rather than guess about it.

NO, the post-64 Model 70 receiver is NOT investment cast. It is forged, then machined.

Now you're thinking of producing a top-grade bolt-gun yourself, right, yet you don't know that the Model 70 isn'nt investment cast? If that's so, pal, you're undergunned..........

AD

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Before I reply to this comment, were you referring to me, or someone else in this discussion????????

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Now you're thinking of producing a top-grade bolt-gun yourself, right, yet you don't know that the Model 70 isn'nt investment cast?

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Investment cast parts are not as strong as parts machined from bar stock, forgings or MIM. The molicule structure is not as close as those of the other processes mentioned.

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