I meant the difference between Carpenter 158 and 9310.Originally Posted by Miale
|
||||||||||||||||||||||||||||||||||||||
Member
I meant the difference between Carpenter 158 and 9310.
Member
ok, understood, my bad. 158 is a strategic metal meaning it can be difficult to obtain, 9310 is not, also 9310 has better corrosion resistance due to a higher nickel content. the point being that both are good materials so as i posted above the material choice is just one part of the overall design.I meant the difference between Carpenter 158 and 9310.
Member
Very interesting thread. I recently purchased the LWD High Performance Bolt specifically because of the obvious problems with the mil-spec design. My background is engineering and materials science, especially high-strength structural steel.
Mil spec has problems. On the one hand, it provides minimum standards for quality and procedures. This is good. On the other hand, it sometimes stagnates development, preventing improved products and materials from being used. This is not so good. In addition, it creates distortions in the market, and encourages legal price gouging. That is bad. These things hurt us and our men in battle.
Instead of being satisfied with making just standard mil-spec bolts, LWD tackled a well-known problem with the mil-spec bolt design, namely early failure, especially in M4's, due to stress cracking resulting from an old, obviously faulty design, and old materials. They then used computer analysis, common sense, and the best materials available to make a better bolt. LWD tested the hell out of their new bolt. Now they sell it with a Life-time guarantee. This is a sample of what makes Western civilization in general, and America in particular, great.
Market facts: Carpenter is a steel manufacturer. That's all it does. It profits most when it sells vast quantities of easily-produced steel at the maximum possible price. It has a vested interest in selling mil-spec 158, and lots of it, to those who have no choice but to buy the specified mil-spec strategic material at mil-spec mandated inflated prices. In contrast to this, LWD doesn't sell bulk steel, it sells products expected to perform beyond mil-spec requirements. But Carpenter cares little or nothing about whether bolts made from 158 steel break prematurely or not. Carpenter has never made or even tested a single bolt, and doesn't warranty any of the bolts manufactured using it's 158 steel. Conversely, LWD provides a lifetime guarantee on the bolt they engineered, tested, and manufactured using 9310. Carpenter's sales and profits are guaranteed by mil-spec mandates, regardless of final product performance, whereas LWD's sales and profits are based solely on the real-world performance their final product. Of the two companies, who's interests is best aligned with our interests?
Nothing against Sniperfrog of course, but the quote from the tech at Carpenter pasted in Sniperfrog's post smelled very fishy, so I contacted LWD to get their side of the story. Below are edited quotes from LWD's response.
Regarding the purported statement by Carpenter, I would observe the following: Carpenter has a vested interest in moving their strategic materials (i.e.158) over their standard materials (i.e.9310) because buyers of strategic materials have no choice but to purchase mill runs in minimum quantities of one ton. Carpenter also charges premium prices for their strategic materials. You should also remember that Carpenter does not actually make bolts. But, because the mil-spec of over 40 years ago requires 158 over the originally specified 8620, they would prefer that manufacturers continue to use 158.
At that time, the change from 8620 to 158 was a good move, but it was a decision based on the original 20 inch barreled rifles and not the shorter carbines which produce higher stresses in bolts. Compared to modern alloys, 158 is a very poor choice for carbine weapons, failing in as little as 3,000 rounds when pushed hard - 9310 is far superior in this respect. Also, since Carpenter has never made or tested any bolts using 9310, I fail to see how anything they say with regard to its use is of any relevance whatsoever. We have manufactured over 25,000 bolts from 9310 and issue a lifetime warranty on the product - we would never do that with a bolt made from 158 that might see use in a carbine. I might add that the first 6.8 bolts supplied by Compass Lake to PRI for the initial development of that round were made by us from 9310 and they have not failed yet.
A couple of years ago, our sister company in the UK was told by Carpenter that their new super alloy (another strategic material) Aermet 100 was the best thing to make bolts from - they now have boxes of them which they cannot use because the bolts (regardless of caliber) all fail at 2,000 rounds +/- 10%.
Industry Professional
Bolts are becoming a pet subject!
It is always interesting to consider the bolt within the context of its application. To do so will draw not only on stress analysis, but also on fatigue theory and metalurgy. This will quickly move the solution beyond the simple question of which steel is best, for the best steel if applied out of context will not perform adequately.
So for simple illustration let us assume that the steels are applied well, before discussing the differences.
Carpenter 158 is without doubt an excellent material for the production of M16 bolts. The material is clean with negliable elements in the make up that are detrimental to the fatigue life. It can operate happily within the confines of the enviromental requirements imposed by the application and has a very low deformation of the parts as they run through heat treatment. The down side to the material is that it was designed to heat treat in large sections so the thin bolt material will respond somewhat voilently. Again not an immediate problem if the heat treatment is absolutely perfect but within the confines of a production enviroment it will throw problems.
By comparison AISI 9310 will on first inspection also make an adequate bolt material. It has several alloy elements that promote a better structure and in the correct heat treatment will provide a slightly higher toughness than Carpenter 158 which is benificial to the fatigue life. Corrosion resistance is slightly higher but as with C158 it should not be applied without some form of surface protection. Thin section response to quenching is somewaht less than C158 which makes it better suited to the manufacture of bolts. However by comparison to Carpenter 158, AISI 9310 has several elements present in its composition that are detrimental to fatigue while not being evident in the physical properties.
It has become evident from the industry that a number of manufacturers have jumped upon the AISI 9310 wagon in order to claim better performance. While in theory an AISI 9310 bolt may perform better I would not typically select this material specification. There are a wide number of superior alloys available without resorting to the nickel based maraging alloys which are expensive, difficult to machine and extremely temperamental in behaviour. The steel industry has advanced since the specification of Carpenter 158 but the basic premises for the selection remain even if the menu has now expanded.
Bill Alexander
Industry Professional
Sorry forgot this.
Is the demon the the mill with the specified material and no context for the application or the manufacturer that has crates of bad parts because they did not understand the problem. Which would you trust.
Bill Alexander
Senior Member
9310 costs about 1/3 the amount of C158. No doubt makers who use it then pretend it is better. It costs a lot because it is expensive to make, whatwith the remelting and all for more purity.
And yes, I trust the Cartech metallurgists more than AR part suppliers. When a metallurgist recommends something, and a part maker pick something more easily available at a lower cost, I am not going to believe it was to get higher performance.
I fully understand AR companies wanting to pick a material they can easily get. The Rock Rivers, Olympic Arms -- they should just use 8620 and crank them out to meet demand. Especially for semi auto use. I personally will pay more for C158.
Last edited by rsilvers; 06-11-09 at 09:33.
Member
we've being manufacturing these particular components since 1957 and carpenter suggested that we use aermet 100 because it would offer better properties for the application. we tried it and unfortunately it failed. now while it may work well for aircraft landing gear which as we discovered is changed after 1,500 cycles, it was not suitable for repeated shock loadings in a component expected to have a service life of 20 years or more.
carpenter are in the business of selling metals and strategic metals offer greater profitability, plus with 158 and aermet you are tied to a single producer. nothing sinister, just business.
Industry Professional
The illustration serves that there is considerably more involved in the production of a bolt than simply the selection of what is on paper an adequate material. A metallurgist will select a material from the perceived application. That application must be correctly conveyed by the customer, but ultimately the customer has to determine the material best suited. AISI 9310 has a number of drawbacks in use for the bolt of an M16 type rifle , not least of which is that in this application the fatigue life is lower than Carpenter 158 as a result of certain tramp elements commonly found in the alloy. This is not to imply that Carpenter 158 is the pinnacle for this application but that AISI 9310 is not optimum either. Both have drawbacks and advantages.
The rush to produce AISI 9310 bolts without an understanding of the problems will create not stronger bolts but those with a wider spread of service life.
A well executed 8620 bolt will outperform a higher alloy if it is not well made and heat treated.
Bill Alexander
Member
we don't make bolts
but referring to my previous post, the material choice is just one part of the overall design and it would seem that certain manufacturers are able to achieve the results they want with different material choices. i've had two carpenter bolts fail at the lugs by the extractor, a common problem; the jp bolts are performing as expected and by virtue of their design in this area, i do not expect a similar failure. that and an improvement in group size, for me in any case, more than justify my decision to purchase.
eta your final observation is of course correct
Last edited by Miale; 06-11-09 at 12:21. Reason: forgot to include
Member
clearly, you guys know more about bolts and metalurgy than I will ever know.
But I do have a question. A good design, one that minimizes stress risers, can allow a designer to create a component with a superior fatigue life, even with inferior materials.
Is there anything about the JP bolts that may provide this kind of product improvement?
Don
Posting Permissions
Reply With Quote
Bookmarks