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+--- Thread: IN STOCK 6mmARC Mk136 Mod2 Bolts (/showthread.php?tid=178)
IN STOCK 6mmARC Mk136 Mod2 Bolts - BluntForceTrauma - 01-12-2021
Guys, our next shipment of Mk136, or Type 2, 6mmARC / 6.5 Grendel bolts with a boltface counterbore depth of 0.136 is due mid April 2021.
These are gonna have a Mod2 design update that you're gonna love!
Bolt bodies are made of 9310 steel and black nitride treated for all-weather durability.
These fit in standard bolt carriers and take standard firing pins.
Cool MONSTER logo laser-etched on the bolt!
NO-BRAINER cost is $69.95 each plus $4 shipping. Get a deal when you combine with our bolt carrier.
ORDER from SixFiveArms.
(Same bolt for 6.5 Grendel, so tell your Grendel buddies!)
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - BluntForceTrauma - 03-24-2021
U P D A T E : Bolt guy got back to me and says "bolts are at heat treat, will be off to QPQ next week. Delivery will be approximately three weeks."
Three weeks from now puts us at about mid April for availability — knock on wood!
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - pavementends - 03-24-2021
(03-24-2021, 03:33 PM)Two builds on hold! A T E : Bolt guy got back to me and says "bolts are at heat treat, will be off to QPQ next week. Delivery will be approximately three weeks. Wrote: Three weeks from now puts us at about mid April for availability — knock on wood!
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - Shoreglide - 03-25-2021
I'll be grabbing one soon as you have them. I think that and a muzzle brake are all I still need for my build.
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - trianglevelvet - 04-11-2021
You guys over at SixFive have sold a bunch of grendel bolts over the years right?
And your bolts are nitrided?
I've got someone on another forum trying to tell me that nitrided grendel bolts are no good and often break due to overly brittle steel caused by nitriding.
I assume that if this was an issue you folks would have encountered it, assuming that a fair amount of your customers reload and occasionally overpressure em.
Is the bolt lug breakage issue basically a problem of the past due to better alloys and better control during the nitriding step?
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - BehindEnemyLines - 04-11-2021
(04-11-2021, 02:03 PM)trianglevelvet Wrote: You guys over at SixFive have sold a bunch of grendel bolts over the years right?
And your bolts are nitrided?
I've got someone on another forum trying to tell me that nitrided grendel bolts are no good and often break due to overly brittle steel caused by nitriding.
I assume that if this was an issue you folks would have encountered it, assuming that a fair amount of your customers reload and occasionally overpressure em.
Is the bolt lug breakage issue basically a problem of the past due to better alloys and better control during the nitriding step?
I'm not affiliated with SixFiveArms, just a satisfied customer with both their service and products. I am the one that posted the information about their bolts after a couple of people were asking about their 20" ARC barrels.
When I saw the comment on the other site from a different user saying to NEVER use nitrided Grendel bolts (and later any nitrided bolt), I contacted SixFiveArms to let them know that I had inadvertently caused a controversy on that site with a post about the information on their MONSTER bolt and that other users are now questioning the nitrided bolts they own that are not even MONSTER branded.
Here is what I got from the owner of SixFiveArms:
They have long been aware of the QPQ bolt embrittlement issue and resolved it a decade ago with the correct heat treatment with the Grendel bolts that they supply.
They've sold thousands of nitrided MONSTER bolts and barrels and they are good to go.
If you do some checking on both the 65Grendel forum and here there are a LOT of people that have bought both barrels and bolts from SixFiveArms and are happy with the products purchased.
If there was a problem with nitrided bolts I would expect to see way more people reporting that they are sub standard.
My 2 cents anyways.
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - BluntForceTrauma - 04-11-2021
TriangleVelvet, my MONSTER bolts use the same manufacturer and heat-treat process as Bill Alexander developed and used back when he was still at Alexander Arms.
They are sort of the industry standard for Grendel bolts — I just sell 'em for $55 when most others are selling them for $75. This guy that is worried about his MONSTER bolts and wonders if he should get a Toolcraft bolt, instead.... Toolcraft doesn't make their own bolts. Their bolt vendor (great guy, chatted with him at SHOT Show) uses boltface walls that are even thinner than my bolts. Go figure.
But, yes, we are aware of the embrittlement problem with nitriding small parts. Our heat treat process is the dark art part of this equation, and eliminates QPQ nitriding as a source of concern on my MONSTER bolts while retaining the benefits of corrosion resistance, strength, and lubricity — all at an attractive price that also does not change the part dimensionally.
You will notice we only provide parkerized extraction claws, because we agree that nitriding would make the small areas of that part too brittle for its task. But the bolt bodies themselves do just fine nitrided, and the history of the industry with these bolts — and my personal history as a vendor — proves this beyond a doubt.
Now, we all know any Grendel or 6ARC bolt is gonna be "weaker" than any 5.56 bolts when one compares amount of steel material in the boltface ring that the lugs sit on. Obviously, it was a simple engineering challenge, and the maximum average pressure of 52,000 that the cartridge was designed for took this into account. Where a 5.56 might have a bolt life of 7,500 rounds, a 65G/6ARC bolt might have a life of 5,000 rounds. Nature of the beast. (I'm not saying anyone has actually rigorously and scientifically tested this — maybe the military entity that requested the 6ARC in the first place?) Of course, all that depends on a hell of a lot of variables.
Nobody was trying to trick anybody or pretend the fatter Grendel (and .50 Beowulf) and now 6ARC cases didn't put different stresses on the bolt than the smaller 5.56 case.
So it is what it is. Meanwhile, tens of thousands of 6.5 Grendel, .50 Beowulf, and 6mmARC shooters have understood the engineering compomises necessary to fit a larger cartridge into the AR15 platform and have successfully engaged with the platform.
Now, to the "rumors," and this is where it gets messy.
There is a vendor who specializes in 6.8 SPC barrels and is kind of a cult-like leader with his customers. I respect the guy's technical knowledge, his work ethic, and his ability to think outside the box. But he believes everyone else in the whole world is an idiot or is trying to cheat him, and he's not above starting nasty rumors to denigrate those in the firearms community he perceives as his competition or his enemies.
He's recently and loudly proclaimed he will no longer nitride bolts cause he says they're unreliable. His acolytes take this as gospel and run with it to various other forums. He's also recently proclaimed he will no longer sell nitrided barrels cause they are also unreliable. Wut?!? So, he's apparently got issues with whoever he uses for nitriding of both his barrels and his bolts. But the fact that he's having issues does not mean the rest of us in the industry are.
We have no such problems with the nitriding of our barrels and our bolts. That's not to say things don't go wrong in the world of manufacturing, let me tell you. Around 2015, for example, when I got Faxon into the Grendel game, I got a batch of barrels where the nitriding had been botched and they had to be replaced.
Long story short: 65G/6ARC bolts are weaker than 5.56 bolts for engineering reasons. This is obvious to everybody; nobody is trying to hide this fact. For those of us who are fans, the performance gains outweigh the engineering compromises that had to be made. While people break 5.56 bolts for various reasons, they are also going to break 65G/6ARC bolts for various reasons. Is it "common" in the 65G/6ARC world? No. Only in the eyes of those who have their own reasons for blowing the issue out of proportion for their own advantage.
Bottom line: If you're gonna shoot 65G/6ARC, you're gonna need a bolt. Personally, my MONSTER bolts are as good as any and better than most and at a lower price, to boot. On the Grendel forum, we've seen every brand break over the years, so there's no "magic" bolt.
Having said that, this next batch due soon — knock on wood — has a slightly thicker lug rim. I call them Mk136 Mod1. And, yes, they'll be nitrided.
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - grayfox - 04-11-2021
Krys, you are much more generous to that one who is hArp-ing so loudly... (note: when your point is weak, shout loud to cover up for it!!).
While I am not expert on how small of a metal part might/might not have problems (and respect the decisions you've made on that), the nitriding process, metallurgically, only goes about 50 millionths of an inch deep (50 microns) and results in a chemical infusion into the surface layers, without changing the dimensions of the steel. The heat treatment, temperatures, soaks, and process would have more to do IMO on a part's brittleness, as well as if there is any pre-existing flaw in the surface. This type of info - on brittle fracture/behavior of steels - is a fairly common topic in my industry. By pre-existing flaw I mean any scratch or crack type of flaw on the surface of the steel. That is where brittle fractures begin; it is much more difficult to induce a brittle failure in the absence of a surface flaw... which would speak therefore to the inspections and quality of their QC, again, more than of any nitriding itself.
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - BluntForceTrauma - 04-11-2021
Gray, excellent points.
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - trianglevelvet - 04-11-2021
Great info in this thread.
I learned some things.
Thanks guys
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - skyrep - 04-12-2021
Thank you for the great write-up. I’ll be ordering two when you get them in. One for my 6.5G and one for the 6ARC.
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - pavementends - 04-12-2021
Good write up. I will also need 2. Will you have them marked 6mm arc?
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - BluntForceTrauma - 04-12-2021
Since it's the same bolt for both 6ARC and 6.5 Grendel, they are marked generically. Has my MONSTER skull logo and text reads: MONSTER / MK136
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - BluntForceTrauma - 04-15-2021
U P D A T E : Bolt guy emails me this morning (Thursday, April 15) and says: "Your bolts are at QPQ, I expect them back next week, then we can assemble and laser within a day."
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - Shoreglide - 04-16-2021
Excellent news!
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - 41bear - 04-25-2021
Thanks for the heads up and, as always, your info/input is well thought out and on point. As for your product, how you are able to sell at your price point yet maintain the quality/accuracy of that product is OUTSTANDING! BRAVO!
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - Bigdaddyjak - 04-28-2021
Still waiting!!
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - Old Bob - 04-28-2021
(04-28-2021, 02:04 AM)Bigdaddyjak Wrote: Still waiting!!
Patience, young grasshopper...
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - Bigdaddyjak - 05-02-2021
Yes , sensi !!! Lol
RE: BOLTS DUE MID APRIL 6mmARC Mk136 Mod2 Bolts - trianglevelvet - 05-03-2021
Waiting for these too.
Just checked website, looks like price for the bolts went up to $75.