Re: One off CNC Parts? Who does them?
The OP and I have chatted a bit via PM's. Where this goes is obviously his decision, but I thought I'd share some of the challenges faced anyone attempting to design/develop/produce a gun part like a bolt/receiver.
Understanding this helps for those uneducated on the hows/whys certain things are done the way they are. Maybe someone will find this useful for a future project.
C.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">No worries.
I guess anything is possible, but my first question would be, why the extra effort? Why not just order up another bolt in a 223 configuration?
Your idea will almost certainly demand that you change the extractor design I imagine. If your going to go with a floating head style like a Savage I don't see it as too good an idea to have the extractor bridging the gap between bolt body/head. Seems like a great place for it to hang up.
You'd have to pull the barrel anyway to make the jump between a .390/.480/.545/.590 case head. Seems like a simple bolt swap would minimize the headaches and expense your going to undertake.
Just my two bits.
As for materials:
4140 heat treated to around 37HRC is prolly the best. Good hardness, lubricity, toughness, and tolerance to heat/abrasion.
Be even better to have it nickel plated or have a nitride process done on it.
Just remember and your engineer buddy will/should back me up on this. You want AT LEAST 5 POINTS of hardness differential between the receiver and the bolt. This is to mitigate galling on the lugs. Rotating a bolt into battery seems like a pretty straight forward process and it is. However over time failure to observe this little rule can and will likely result in the parts ultimately failing. There's significant shear loading with an action that's a partial cock on open/close fire control design. You need the hardness differential to have it last.
3 lugs do spread the load over a broader footprint than a twin lug does, but the surface area increase over a twin lug isn't that much greater. Not enough to ignore the problem anyway. Don't forget also that a 3 lug system has a 60* bolt lift where's a twin lug has a 90*. That means the ramp angles are more aggressive when resetting the fire control. This is at the back of the bolt and has little to do with up front, but it does still emphasize the importance of the hardness differential because the striker assy has to move the same distance in less rotation. Gotta make sure the material conditions are jonny on the spot otherwise your going to have a nasty mess that can easily result in a bolt stuck in the receiver.
Good luck and hope it works. I'd still opt for a new bolt though.
C.</div></div>
