How does this bolt stack up?

[ABNAK]

I'm pretty AR-aware, been here and using the AR for long enough to know better!

I have a box-o-parts, kinda large. In there, among many other things, is a big ziplock bag dedicated to the BCG. Several complete BCG's and parts.

One of the bolts I have accumulated is a Young Manufacturing chromed NM 9310 SAE bolt, which has been MPI tested. Question: Young is generally regarded as a "higher end" AR parts manufacturer. The bolt in question is 9310 SAE as opposed to 158 Carpenter. How well should one expect this bolt to hold up? I'm not interested in an estimate based on "It will work for most AR shooters". How would you estimate it would hold up under adverse conditions, like combat?

This one:

https://youngmanufacturing.net/product/national-match-chrome-556-bolt/

[MegademiC]

If the processing was sound, should last as long as any other quality bolt.

If you are worried about it, throw another bolt in the grip and inspect each outing.

If we are taking bets, id say you wont notice any difference vs anything else, maybe easier to clean.
Being NM, was this headspaced to match a barrel? Perhaps some issue with a tight chamber, but Id imagine that would be evident right off the bat.

[Straight Shooter]

From my reading & inquiry on the subject, Ive been told a "properly treated" 9310 bolt is about 10% stronger than an equal Carp. 158.
I DONT KNOW..this is what Ive read from some who supposedly do.
I do know..Im getting a YOUNG NM BCG for my 20" build Im putting together slowly. I believe youve got a hellava good bolt there, and Id use it all day...errday.

[turnburglar]

Bill G. recently said; while taking about his new nano bolt, that he has a testing machine that can simulate round counts. The 'commercial' (I read as 9310) bolts last 12k. He says that the 'milspec' bolts (I read as C158) are averaging 20k.

Estimating the cost of ammo at $0.30 I figured you would burn $3,600 in ammo before the weaker bolts break, where as a milspec bolt will last $6,000 in ammo.

[Straight Shooter]

Bill G. recently said; while taking about his new nano bolt, that he has a testing machine that can simulate round counts. The 'commercial' (I read as 9310) bolts last 12k. He says that the 'milspec' bolts (I read as C158) are averaging 20k.

Estimating the cost of ammo at $0.30 I figured you would burn $3,600 in ammo before the weaker bolts break, where as a milspec bolt will last $6,000 in ammo.

Id be very interested in hearing or watching that..is it on video somewhere?

[MorphCross]

Id be very interested in hearing or watching that..is it on video somewhere?

Brownells YouTube video that featured his ShotShow 2019 lineup. He also mentions the bolt that he will be including in the Super Duty as being made from a forging and having a "ridiculous" round life.

[Straight Shooter]

Brownells YouTube video that featured his ShotShow 2019 lineup. He also mentions the bolt that he will be including in the Super Duty as being made from a forging and having a "ridiculous" round life.

Good deal, thank you!

[26 Inf]

Id be very interested in hearing or watching that..is it on video somewhere?

Here it is, he starts talking about the AR at 11:40 and the bolt longevity at 15:40: https://www.youtube.com/watch?v=hxjEdj8Z5kE

He doesn't actually mention 9310 anyplace, instead using the term 'you can put the bolts that you buy on line, that aren't very expensive, 12,000 rounds' and 'you put a mil-spec bolt in, from one of the main suppliers, 20.000.'

Here are some snippets I've found while exploring the subject, I still buy C-158 bolts, waiting for a widely recognized quality vendor to offer 9310 before I try one:


In the case of the M16 family, the US military selected a steel called Carpenter 158 (also known as "C158" or "Car 158") to be used for manufacturing the bolt. Therefore, any AR15 or M16 bolts that claim to follow military specifications (or "mil-spec" for short) should be made of C158 steel as one of the requirements.

The interesting thing about Carpenter 158 is that it is a proprietary steel alloy and its formula and method of manufacturing are not publicly defined. Therefore, there is no SAE standard for it and the sole manufacturer of this steel is a company called Carpenter Technology in Pennsylvania. They do not manufacture this steel continuously and only do a certain number of mill runs per year, which means it is not always available. They also only sell this steel in large amounts and require the customer to buy a lot of it at a time. Therefore, only large companies like Colt, Fabrique Nationale (FN), Daniel Defense etc. can afford to buy this steel.

However, C158 isn't the only steel alloy used to make bolts. Bear in mind that the US military selected C158 in the 1960s and there have been other (and sometimes better) steel alloys developed since then. For instance, some manufacturers use 9310 or 8620 steels to make bolts.

The advantage of these steels is that their chemical compositions and manufacturing methods are publicly specified by SAE (Society of Automotive Engineers - the organization responsible for specifying standards for different grades of steel in the US) and there are many manufacturers of these steels. Therefore, supply is less of a problem. Also, 9310 and 8620 steels can be purchased in small quantities and are therefore suitable for smaller manufacturers who cannot afford to buy large amounts of C158 steel at one time. If machined and heat treated properly afterwards, bolts made of 9310 steel can be even better than C158 steel.

Another steel alloy used for bolts by some manufacturers is Aermet 100 (which is also used in the landing gear of jet fighters aboard US aircraft carriers). This is actually another proprietary steel alloy made by Carpenter Technology and is reputed to be far superior to C158 and 9310 steels. However, it requires a double hardening treatment process after machining to reach its full potential. In general, bolts made of 9310 steel are the cheapest to produce, followed by bolts made of C158 steel, and bolts made of Aermet steel are the most expensive. However, bolts for AR15/M16 made of 9310 or Aermet 100 cannot be called "mil-spec" even if they exceed the military standard specifications, since the US military specification says that only C158 steel should be used for the bolt of a M16.

Another snippet: The reason for Carpenter 158 as the "Mil-Spec" is rooted in history when the AR-15, chambered for the lower pressure .223 Remington round was upgraded to the higher pressure 5.56 NATO loads. The original material selection for the bolt (my note: 8620) was found to have inadequate service life. The military went searching for better material, constrained by the size of the bolt. Carpenter Technologies' 158 blend of steel was selected as it provided adequate strength and wear characteristics. It has been the "Mil-Spec" since.

Since the creation of Carpenter 158, the metals industry has continued to innovate, creating new blends of steels. 9310 is a AISI standard grade of tool steel that makes it about ~7% stronger than "mil-spec" Carpenter 158 steels, when appropriately treated. Its commonly used in the aerospace industry where toughness, impact strength, and solid wear characteristics are required.

Snippet three: 9310 material is used for a few reasons:

It's sold in round stock and it can be hard turned. It also is a high nickle steel and can be chrome plated with less issues with breaking. Because of its high nickle content it is less brittle......158 is cheaper but 9310 can be purchased in lower amounts, which for most manufactures is even more important.

[ABNAK]

Brownells YouTube video that featured his ShotShow 2019 lineup. He also mentions the bolt that he will be including in the Super Duty as being made from a forging and having a "ridiculous" round life.

I wonder if those Geissele bolts are available yet?

[ABNAK]

As to the Young bolt this thread is about, this is from the link I posted in the OP:

Our National Match Chrome 5.56mm bolt is made from SAE 9310 steel and Precision Ground in three critical areas after heat treating to Mil- Spec. This provides the most accurate fit possible on the center support ring, and the bolt tail. Grinding the back of the lugs true to the bolt face gives you a bolt that locks up true and square to the center of the bore. All of our bolts are Mag Particle Inspected to detect any stress fractures that might occur during the heat treat process.

So it looks like they do some heat treat, to mil-spec if you read their info.

[lysander]

As to the Young bolt this thread is about, this is from the link I posted in the OP:

Our National Match Chrome 5.56mm bolt is made from SAE 9310 steel and Precision Ground in three critical areas after heat treating to Mil- Spec. This provides the most accurate fit possible on the center support ring, and the bolt tail. Grinding the back of the lugs true to the bolt face gives you a bolt that locks up true and square to the center of the bore. All of our bolts are Mag Particle Inspected to detect any stress fractures that might occur during the heat treat process.

So it looks like they do some heat treat, to mil-spec if you read their info.
A little advertising license here...

If you look at the drawing for the bolt (you can find it floating around the internet), it specifically states to grind five places after heat treatment: the tail of the bolt, the 0.4880" gas ring diameter, the 0.5280" ring swell, the rear face of the lugs, and the 0.5500" diameter aft of the lugs. The plane that is the rear face of the lugs are supposed to be ground to within half of one ten-thousandths of an inch.