Melonite Process

Tricky, I turn and mill 4130 & 4350 , in their hardened state, every day. Roughing cuts on the lathe .06 deep @ .008-.01 I.P.R. Most all milling is done on CNC mills, machines so much larger than Bridgeports the only compairison is they both use end mill type cutters, some inserted some not. C6 brazed carbide easily cuts through Melonited surfaces , like a barrel crowns. Good inserts, even better. My question is why would an action need to be harder? Most items that take a "shock" are designed to have a certain amount of "spring back" to them, so they return to their original shape (like an axle does). I think if I read H&Ms' policys correctly you'll find that they claim no responsibility for the suitability or application of the part(s) being treated. In the past Meoniting was mainly used on bearing surfaces (the rifled bore of a barrel is a "bearing surface"as are crank shafts and cam shafts in large, industrial applications). 4140/416R can be ordered from the mill in any hardness obtainable, as long as the order is large enough. By what I read on the boards, few understand that modern bolt actions are made of pre-hardened stock (so are barrels), not hardened after they are machined. The uneven sections would allow too much deflection if hardened after machining. I'm not against advances in technology, I'm just questioning "does an action need to be any harder than it already is?".
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perhaps Flip will chime in as he way ahead of me in what goes on in a steel mill. I would like to think that generic 4150 pretreat steel is way over the top in the application of a rifle receiver. Yet on the otherhand I might want a bolt seating face somewhat harder than 30rc, and think a 45rc-47rc to be about right with a .015" case. The problem here is that I may not want the rest of the action to be that hard. A soft core is needed here. This is why I would use a dead soft grade of something like 4350, and machine it in two steps with the bolt seat being the hardest part at 47rc.

Buying steel is not like going to Walmart. Every manufacturer of a pretreat steel has it's own process and alloy. I'd personally go with a certified lot from Baldwin Steel out of PA, or maybe con Timken into being a single source supplier for my steel needs (Timken is the best steel money can buy, and almost always comes in cheaper after machining processes are done). But I've always found the heat treat processes from Baldwin to be nearly perfection. About twenty percent more money, but you usually get what you paid for. For a rifle action, and some other critical items used elsewhere; I would spec a certified lot of steel. More money I know, but you know what you got from the first piece to the very last piece. Very important. Plus the real money is in the machining process, and never the materials.

Hard turning is nothing really special once you learn the art. Some brands of steel will of course turn better, and other are crap (mostly Asian). If I had to make the part right from the get go, I always picked up the phone and ordered it from Baldwin. A typical five to seven step process of machining a part adds a serious amount of labor & machine time, so you don't want any surprises there. Yet the classic rifle action is a three step process at the max with the right equipment.

Now as many of you already know, I'm not a fan of 416 Stainless steel. It's got more issues than benefits, but does machine well. Nobody in industrial aps would think of buying it! Perhaps 420 or 410, and even then there's better stuff out there. I'm a big fan of MAR-10 (a trade name from Baldwin), and it's nothing but a pretreat 17PH-4 stainless steel. Hard to get better than that! But machining
17PH-4 is a learning curve from the get go. MAR-10 is another learning curve, and expect to be educated as this stuff is tough and extremely strong. Also rather expensive, but you get what you ay for.
gary
 
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So if a guy wanted to make the best of the best with whichever action and barrel he chose, he should have all the machine work completed then have the barrel and action Cryonized then have the barrel, reciever and bolt body Melonited . . As long as the metal work in the barrel and action ( blue printing, lugs lapped) ahead of time it seems the longevity would be at maximum a guy could expect. And when the barrel was changed the action would not need anything done to it.

On my stainless Ruger M77 mk2 that started life as a 338 then after about 2,000 rounds I had it rebarreled to 458 Win Mag and shot around another 2,000 rounds thru it . The head space has grown to over max. I would say conservatively I've cycled the action 20,000 times. So I want to avoid that on a custom build.
 
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