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DPMS Type Bolts - Carpenter 158 or 9310


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I have been partial to the Carpenter 158 material for bolts but, there are quite a few available in 9310 

I know 9310 alloy steel is very strong (they make differential ring and pinion gears for professional class drag racing cars

from it!) but on the M16/M4 the mil-spec is C158 - what is the preferred material for the .308 platform? any epic failure stories?


Looks like I may have to find a temporary BCG since Shadow ops won't have mine out the door till at least late August.

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You need to look back at the days that/when the Technical Data Package (TDP) was approved for the M16, or more recently, for the Colt M4/M4A1. 


At those times, in those days (it goes to the M16), C158 was a damn strong material, and that's what they deemed was necessary for the material for the bolt - at that time. 


Other materials have been made since then, of superior quality and strength, that surpass C158.


It's up to you to determine if your bolt manufacturer is making bolts that meet or exceed that minimum standard of what's required from C158. 

Edited by 98Z5V
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OK, Thanks for confirming  my suspicions, it's a combination of proper design, material type and quality, and proper heat treating - the last being

critical to preventing a premature failure! I have some experience with exotic steel alloys, for example I use 300M (originally developed for landing gear on carrier based aircraft) for pivot pins on a large piece of mining equipment I manufacture and have found that for my application a hardness of 45-47 on the Rockwell "C" scale is optimum, if I go much higher the pins become too brittle and break, much lower and they will bend! So proper heat treat for the material and application" is key to preventing failure Also I've noticed that some "manufacturers" don't actually manufacture the parts themselves (becomes apparent when they indicate they are waiting for the next "batch" to come in) The ones that do may not be willing to divulge the specifics on 

their manufacturing process.

What a can of worms!


I am curious to know what you guys prefer and perhaps the reason for your choice?


Thanks again!

Edited by guruofhotrod
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If you thought picking out a BCG was a hard one , the Hand guard will be more time consuming .

LOL, I already ordered and paid for a Shadow Ops BCG back at the end of March but, they have had some trouble keeping up with demand so, I decided to buy a "temporary" BCG to allow me to finish my build sooner - I was curious about what bolt material is a more popular choice and if any of the more experienced guys had any advice/suggestions on that subject. I'm leaning toward a keymod type handguard, perhaps the Midwest Industries or maybe the new Fortis, I do like the stuff that Ranier has for the AR15's if they were only available for the high profile DPMS I'd go for it

Edited by guruofhotrod
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