C158 Bolts vs. MPI

[alx01]

So...my $49 Toolcraft, Palmetto State Nitrided 9310 bolts will probably not blow up and destroy the entire planet anytime soon?

I think it has more to do with the design of the bolt and stress points. AK/PKM use a fairly simple materials compared to C158, but it can do that because of the robust and overbuilt design. I suspect that a lot of machine gun bolts will be fine even with the simple 8620 or like type of material.

[alx01]

Just wondering: Do you know if a KAC bolt lugs dimensionally are thinner at the top and wider at the bottom (besides being radiused at both ends) vs a standard bolt? Does it help to alleviate such stress points vs a regular bolt, as pictured?

[lysander]

I am not privy to KAC's bolt geometry, so I cannot answer that.

However, making a stress model of a bolt, and optimizing the geometry to make the little red areas go away is well within the ability of any good engineering firm (or engineering college).

[lysander]

I think it has more to do with the design of the bolt and stress points. AK/PKM use a fairly simple materials compared to C158, but it can do that because of the robust and overbuilt design. I suspect that a lot of machine gun bolts will be fine even with the simple 8620 or like type of material.

The physical properties of 9310 are very similar to C158. The one thing all the makers that use exclusively use C158 tell you is that 9310 does not have as good fatigue properties, which is at best, a half-truth.

The fatigue properties of 9310 can be brought to levels comparable to of better than C158 or 8620 by simply bringing it to a temperature below -100 degrees F for a few hours. It is very popular for gears.

No, bolts made from 9310 are not going to blow-up and destroy the world anytime soon.

[10MMGary]

And where do Palmetto State Armory bolts rate? (I'll take a guess: Hobby Grade).

I can only talk about mine and they both were C158 & HP/MPI stamped I also have Two DD BCGs with bolts marked MPI or MI I forget which but no HPT stamping or testing. I really lucked out when I bought my wrong handed Stag as it's barrel is stamped 5.56 NATO 1/7 HPT-MPI as is the left handed bolt. Also m-16 profile carriers came with all.