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Thread: .30-'06 conversion notes

  1. #41
    Gunco Regular mrtank's Avatar
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    Order Alloy Steel 4140 Round in Small Quantities at OnlineMetals.com For the 4140.

    Did a little digging showing the dpms bolt head is carpenter 158 steel. Carpenter No. 158 Plastic Mold Steel

    Another thread I ran into Why no improved AR bolts? - THR

  2. #42
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    Carpenter is a specialty steel maker. Anything you buy that's much more exotic than plain old chicken-wire grade steel is likely to be from Carpenter.

    I got my 4140 from a local steelyard. There are several online sources that will sell a foot or two. As an end user, steel looks pretty much like steel; any legitimate seller should be able to provide a "test report" showing the chemical analysis of the melt the bar came from. The test reports are generally furnished at no charge, but you have to ask for them. Not that you could tell the difference, but it increases the likelihood of the warehouse guy cutting a piece off the correct bar.

  3. #43
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    Doing some net.searching...

    4140: S&W rifles, Hesse .50, Weatherby rifles

    4350: Surgeon, DuBiel actions

    8620: M1 Garand, M14, some '03 replacements, Barrett .50, some aftermarket AR-15

    9310: some aftermarket AR-15

    4140 and 4350 are deep-hardening alloys. 8620 and 9310 are case-hardenable.

  4. #44
    No Hope For Me 1biggun's Avatar
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    Another thread I ran into Why no improved AR bolts? - THR
    they sure have a lot of excusses on wy there AR15/ m16 bolts brake every thing from dry firing to heat from the round to poor design to many rounds fired BLA BLA BLA then they compare the AK bolt in a PIC and say it has three lugs when it only has two.

    try to find 10 documented cases of AK bolt failure on the net its pretty hard Ive looked. more reason I think the AK can run at considerably higher pressures than the AR.

    What ever the new AK super bolt is it needs to be made out of the best steel. Id like to see it handel 65,000 PSI with .500 bolt face and proof beyond that. Not sure what the m70 trunon can take but there are even less failures of trunion than AK bolts that I have found documented. If any.

  5. #45
    Happy Camper hcpookie's Avatar
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    Yeah I noticed that too lol - "its just a service rifle not meant to last" is what I took away from all that

    Thanks on the Carpenter reference - now I undersatnd! What are your thoughts on the 4340? I built my USA VZ-58 FCG parts from it and basically used a grinder and carbide bits for everything. Possible it could be too hard/brittle? 1 foot of .875" 4140 is only $8.00 so I may just order some because I can

    Interesting that some of these steels are described as case hardening steels. I figured they'd all be "fully" hardened... is that what its called? Case hardening doesn't seem correct for this application so perhaps they mean simply that it has certain characteristics vs. fully hardened. Most interesting!
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  6. #46
    No Hope For Me 1biggun's Avatar
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    Im not the guy to specify what steels to use. I have some basic heat treating skills learned in metal shop way to long ago and some knoledge from years of racing but I would not feel comfortable doing the heat treating

    If you read all she specifices in that link it says that the carpnter steel can be fully heat treated and gives draw times and this and that that are way over my head and abilitys.

    The heat treating is what has stoped me from compleating my 50 BMG build. Im not going to but my or anyone elses life on the line based on my heat treating knowledge. heat untill a magnet dont stic and quench in oil while stiring and then re heat untill it turns purple if you want to then soften it is all I really know. dipping hot metal into carbon powder is how you case harden as I recall

  7. #47
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    Generally, steels are either hard or tough. You need hardness to reduce wear, you need tough to handle shock loads. Sometimes you want both, so you case-harden a part on the outside, while leaving the inside softer, so it can flex a bit under load, but not enough that the hard outer layer will crack.

    Working with a rifle bolt, I'd start soft, watch for lug setback in use, and then try another bolt at a harder treatment, etc. until I didn't see signs of wear. It's not like you can open up an engineering book and find "heat treatment for locking lugs" in the index.

  8. #48
    Always sore, always tired Bradrock's Avatar
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    So............Can your basic Rockwell hardness tester tell the difference between case/surface hardening & deep heat treat?
    " Save a tree...........Eat A Beaver!"

  9. #49
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    Saiga bolt discussion and pictures:

    http://www.gunco.net/forums/f277/bol...a-308-a-43637/

    more Saiga bolt stuff:
    (I had wondered about the corner on the back of the third lug, and how it might dig into the shoulder of the case as the bolt moved back...)
    3rd lug Saiga vs PSL Bolt. - forum.Saiga-12.com
    round gouging on 308 - forum.Saiga-12.com
    Have a weird jamming problem. - forum.Saiga-12.com - Page 2


    BTW, looking at my Yugo trunnion and bolt, if you make the cartridge ramp into a third lug, only the left side engages the mating lug on the trunnion. It's about as much area as the regular top lug, though.

    (more searching on saiga-12.com...) looks like there were quite a few variants of .308 Saiga bolts. On some, the third lug was a big square block, that sometimes smashed the shoulder of a cartridge as it slid back. Later ones were beveled a bit at the back. Still others have a small bevel on the left, where it contacts the trunnion, while the right side is ground down into a ramp similar to a standard AKM bolt.

    I also note the extractor is different on the Saiga bolt; it fits into a slot instead of a hole.

  10. #50
    No Hope For Me 1biggun's Avatar
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    here is mine
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