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Broken bolts- thing of the past? - Printable Version

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Broken bolts- thing of the past? - montana - 03-30-2019

A5BLASTER Wrote:That's perrty cool thinking. But how would that make the bolt lugs stronger and less prone to breaking?

I think what they mean is it helps prevent bolt problems at the cam pin hole.

That's what it meant, it would take a bigger bolt to stop the lugs from breaking.

Broken bolts- thing of the past? - SHORT-N-SASSY - 03-30-2019

LR1955 Wrote:rwh;

Personally, I believe it is basically not enough steel on the bolt when using a fat cartridge like a Grendel. Wish it wasn't so but you get to the point where you can't remove any more metal or even the slightest variation in something breaks the part. So guys spend a lot of effort ensuring everything is absolutely perfect when they build a Grendel upper and those uppers work but I dare say that no matter what you do with one, it will not last half as long as a average rack grade 5.56 bolt. I have come to the conclusion that those are the facts and if you want to enjoy a Grendel, have a spare bolt ready to go.

LR55

And, in addition to the CMMG Anvil, as pointed out by sneaky one, the up-coming Faxon Firearms ARAK-21 6.5mm Grendel:

[Image: Faxon-Bolts.png]
< https://www.65grendel.com/forum/showthread.php?9824-Good-News-from-Faxon-Firearms!&p=108197&viewfull=1#post108197 >

Broken bolts- thing of the past? - centerfire - 03-30-2019

I've said it before but it bears repeating, once you take the Grendel out of the AR15 the cartridge loses its appeal quickly. Either make it work in the platform or find another cartridge. Redesigning the platform around the Grendel is a fool's errand. The Anvil might be the exception but unless they make the barrel extensions open source you're stuck with low quality barrels. My AR308 shoots every bit as well as my AR15 Grendel, 6.5CM is very workable in a platform close to the size of a Grendel without any proprietary parts.

Broken bolts- thing of the past? - LR1955 - 03-30-2019

SHORT-N-SASSY Wrote:And, in addition to the CMMG Anvil, as pointed out by sneaky one, the up-coming Faxon Firearms ARAK-21 6.5mm Grendel:

[Image: Faxon-Bolts.png]
< https://www.65grendel.com/forum/showthread.php?9824-Good-News-from-Faxon-Firearms!&p=108197&viewfull=1#post108197 >

SAS:

Does this mean that one can now take the Grendel above the '55k' level without something blowing apart or breaking? If so, this is a major improvement.

LR55

Broken bolts- thing of the past? - A5BLASTER - 03-30-2019

LR1955 Wrote:SAS:

Does this mean that one can now take the Grendel above the '55k' level without something blowing apart or breaking? If so, this is a major improvement.

LR55

Link is dated 2015.

Broken bolts- thing of the past? - SHORT-N-SASSY - 03-30-2019

LR1955 Wrote:rwh;

Personally, I believe it is basically not enough steel on the bolt when using a fat cartridge like a Grendel. . . .

LR55


LR55,

The respective Bolt designs of the CMMG Anvil and upcoming ARAK-21 satisfy the larger Bolt concept for the 6.5mm Grendel cartridge (Case Rim Diameter: 0.447"), compared to the 5.56x45mm cartridge (Case Rim Diameter: 0.378").

Broken bolts- thing of the past? - brian y - 03-31-2019

Getting close to 4k down my Odin Works barrel with an Odin Works bolt and no problems.

Broken bolts- thing of the past? - biodsl - 11-12-2022

Broke a bolt yesterday. I was shooting my usual loading of 31.2grs of CFE223 under a 123 Nosler CC @2.245"

I don't know the manufacturer of the bolt. I've been using it so long I just can't remember where I got it. I have at least 4,000 rounds on it.

It has been replaced with a Monster Mk136 bolt!

[ATTACH=CONFIG]19300[/ATTACH]

Broken bolts- thing of the past? - lazyengineer - 11-12-2022

biodsl Wrote:Broke a bolt yesterday. I was shooting my usual loading of 31.2grs of CFE223 under a 123 Nosler CC @2.245"

I don't know the manufacturer of the bolt. I've been using it so long I just can't remember where I got it. I have at least 4,000 rounds on it.

It has been replaced with a Monster Mk136 bolt!

[ATTACH=CONFIG]19300[/ATTACH]

Thanks for the update. I'm not familiar with the 4 radial grooves cut into the bolt body, that go around it like that. Does anyone else know what brand that likely is?

Broken bolts- thing of the past? - 41bear - 11-12-2022

lazyengineer Wrote:Thanks for the update. I'm not familiar with the 4 radial grooves cut into the bolt body, that go around it like that. Does anyone else know what brand that likely is?

That's a Maxim Bolt, pictured here.

http://www.maximfirearms.com/online-store/complete-6mm-arc-advanced-rifle-cartridge-bolt/

Broken bolts- thing of the past? - biodsl - 11-12-2022

That makes sense. This is the bolt I was using on my group-buy Lilja many years ago. I see Lilja still mentions Maxim bolts on their website. My approximate round count is correct then.

Broken bolts- thing of the past? - LRRPF52 - 11-12-2022

biodsl Wrote:Broke a bolt yesterday. I was shooting my usual loading of 31.2grs of CFE223 under a 123 Nosler CC @2.245"

I don't know the manufacturer of the bolt. I've been using it so long I just can't remember where I got it. I have at least 4,000 rounds on it.

It has been replaced with a Monster Mk136 bolt!

[ATTACH=CONFIG]19300[/ATTACH]

Was this on an 18” MLGS by chance?

Broken bolts- thing of the past? - biodsl - 11-12-2022

lrrpf52 Wrote:was this on an 18” mlgs by chance?

22" bhw RLGS.

I have an 18" Lilja 319 in the closest. What should I know when I assemble it?

Broken bolts- thing of the past? - LRRPF52 - 11-13-2022

biodsl Wrote:22" bhw RLGS.

I have an 18" Lilja 319 in the closest. What should I know when I assemble it?

Interesting. What’s your gas port diameter on that 22” RLGS?

The thing I’ve seen consistently is that 18” MLGS has a lot of plug dwell time, so the port can’t be too large, and it’s something where I would consider choking the gas even on a basic set-up.

I dropped a Bootleg Adjustable Gas carrier into my 17.6” Lilja, for example.

I would also use buffer mass as a rate reducer.

Make sure the receiver face is square, and regulate the gas to allow residual pressure to subside before unlocking.

The torsional load (rotational stress) on the lugs combined with axial (in-line) bolt thrust combine to make life hard on bolt lugs when the action is not timed properly.

SOCOM has experienced the most bolt failures on suppressed 14.5” and 10.25” carbines, generally seeing about half the bolt life of an unsuppressed 14.5” M4A1.

There’s a new CNC-peening process that increases M4 bolt durability by 100%, so I would like to see that incorporated into bolt manufacturing from hereon-forward across the board, regardless of chambering.

I personally have only broken 5.56 bolts in carbines that I ran through pretty abusive high-volume range sessions, and I have only cracked bolts at the cam pin hole after 10,000 rounds of 400-1100rd/day range sessions.