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Where Are Bolts Manufactured ?


BeeKay
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Just curious about what the inside story is on bolt production.

It seems like it's a part with very exact tolerances and metalluryy specs so they must come from a central source ....  Just guessing.

I'd be interested in finding more info on that.

 

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Toolcraft makes big portion of them on the market. D Wilson was a maker years back that gave a forum discount, he in the precision business making them for other companies, doesn't sell to the public any longer though so I don't know if he still puts out BCG's

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Toolcraft is is biggest supplier to OEMs.  Back in the day CMT was the biggest supplier to OEMs on 5.56 stuff.  Continental Machine Tool. One of the companies under CMT was Stag Arms.  Dad owned CMT, son owned Stag. 

That's different now.  White Wolf Capital.  Here's a rundown on that stuff:

This all went down around the timeframe that Aero "started using their own BCGS" in their guns, rather than using ToolCraft BCGs.  Makes sense, connecting the dots. 

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I have three BCGs and  two of the bolts are marked with MPI and the other is marked with MP.

I'm not sure whether that indicates the manufacturer or some other spec.

I do get correct headspacing when I use the MPI bolt with a particular .308 barrel, When testong it with GO / NO-GO Gauges.     But the bolt that works with that Barrel isn't the one that originally came in that Bolt Carrier.   It seems to be a proper fit, though.

I have a couple side charging BCGs and the other is a rear charging so swapping the entire BCG is out

All feedback appreciated 

Edited by BeeKay
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1 hour ago, BeeKay said:

I have three BCGs and  two of the bolts are marked with MPI and the other is marked with MP.

It's MPI and HP.  Not MP.  Magnetic Particle Inspected, AFTER firing a High Pressure round - HP - a "proof load". 

That does not indicate a manufacturer, it's just proof that it's tested for MPI after HP - if it's even done.  Lots of manufacturers pay for that process, and mark their bolts as such.  It's also not done on every bolt in the batch, for alot of manufacturers - that's what "batch testing" is about in this industry.  They might test 2 out of 100, 47 out of 50 - you don't know unless you contact them directly and ask. 

Closest I can find, and they cut off the MPI to MP...

https://cdn11.bigcommerce.com/s-16115g8ghe/images/stencil/1280x1280/products/1673/9088/STCK6827-2-2__76958.1581175598.jpg?c=1

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10 hours ago, 98Z5V said:

It's MPI and HP.  Not MP.  Magnetic Particle Inspected, AFTER firing a High Pressure round - HP - a "proof load". 

That does not indicate a manufacturer, it's just proof that it's tested for MPI after HP - if it's even done.  Lots of manufacturers pay for that process, and mark their bolts as such.  It's also not done on every bolt in the batch, for alot of manufacturers - that's what "batch testing" is about in this industry.  They might test 2 out of 100, 47 out of 50 - you don't know unless you contact them directly and ask. 

Closest I can find, and they cut off the MPI to MP...

https://cdn11.bigcommerce.com/s-16115g8ghe/images/stencil/1280x1280/products/1673/9088/STCK6827-2-2__76958.1581175598.jpg?c=1

One issue that happens with steel is a flaw of some kind that was in the original poured billet. That billet gets rolled out into bar stock and the flaw will often be present in every bar of steel rolled out of that billet. At a prior employer we made some fairly large parts out of 4140 pre heat treat which is typically 28-32 rockwell hardness. Parts maybe 24" diameter with a LOT of cnc lathe and mill work on them. Far more than once partway through the process they would find cracks in the parts being machined. 

A pistol smith I know used to make a lot of 1911 muzzle brakes, again 4140 pre heat treat steel. He had a half dozen of them that he had a lot of hours into and a crack showed up after bluing, it was in the same exact area on each brake because that flaw ran throughout the whole bar of stock he had purchased.

 

Bill

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I don't know of any reason why you shouldn't be able to swap out 'standard' bolts from one carrier to another. That's regardless of whether the carrier is side charging or rear charging.

There may be some 'optimized' or proprietary bolt designs that don't swap without swapping the cam pin as well but those are pretty few and far between. If you have one of those you probably know it.

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