Hopefully this will be the ultimate bolt life discussion thread...

[Pasta123]

This is the absolute essence of the American Mediocrity Syndrome that pollutes our production and design. Now I don't believe that the same country that blew up two space shuttles can build a decent automobile if their lives depended on it. But the Toiled flapper is a perfect example of the American culture of building garbage because most imbeciles will accept it. Shit! People still buy Chevy, Dodge and Ford garbage every day!

When it comes to ARs, there's certainly a large portion of buyers who just bee-bop into a gun store and are happy with some LWRC trash. Guy on this forum at least attempt to seek out the better/best option for the buck.

I don't know, there's SpaceX. Do Europeans even launch rockets at this point?

But I see your point. Yes, good working men and women in this country are decreasing YoY. Still, last time I chat with my buddy in China, the birth rate expected to drop to 8M (that's a 1.45B country), so we'll see, I still have high hopes here.

[Pasta123]

The people who had premature bolt failures may have just gotten a poorly heat treated batch. They also used their guns in an unusually harsh manner.

The average or even moderately abused civilian AR doesn’t even break the cheapest nitride bolt with any regularly that I’ve seen.

That leads back to #1, where we don't exactly know how they're using their weapons. The most outrageous claim I've heard is from the Battlefield LV where he claims his SCAR survived 200K.

I've asked Lysander once, he thinks 100K is already an impossible goal for any bolt design.

[bruin]

I appreciate you resuming this conversation, though I get the sense it's been thought about quite a bit in the past. Maybe nowadays bolt breakage isn't as hot of an issue as before, with more reasonable gas port sizes, AGBs, trending toward longer gas systems, etc.

As an aside it would be cool if someone made an unpowered round counter that could be attached to the upper, like those mechanical step counters you can clip to your belt. An upper odometer, if you will. A recommended inspection and parts replacement schedule can be adjusted for the upper's configuration (i.e. 20" barrel vs overgassed 10.5”).

Sent from my Pixel 6 Pro using Tapatalk

[constructor]

Wow, that's a lot of drama for a small improvement.

How's the compatibility with your new design?

That's the deal when all barrel extensions are the same the bolt has to work with them and that limits your design. It doesn't have to be exactly like the mil spec but it has to be close.

The other 3 designs I had used barrel extensions that matched the bolt but that only works for people who are having custom barrels made or can buy barrels without the extension installed and gas port drilled..

Back around 2010 9310 was the new alloy to use in bolts now that alloy has doubled in price. Any high strength alloy will be much more expensive than it was 10 years ago.

[gaijin]

Easy button; carry spare MILSPEC Bolt, maybe even BCG.

I’m amazed at the “operators” showing up for Drills classes with Med gear, PEQs, etc.- but no spare bolt?
Maybe even a back up Carbine?

[Pasta123]

That's the deal when all barrel extensions are the same the bolt has to work with them and that limits your design. It doesn't have to be exactly like the mil spec but it has to be close.

The other 3 designs I had used barrel extensions that matched the bolt but that only works for people who are having custom barrels made or can buy barrels without the extension installed and gas port drilled..

Back around 2010 9310 was the new alloy to use in bolts now that alloy has doubled in price. Any high strength alloy will be much more expensive than it was 10 years ago.

Speaking of price, Are all the decent enhanced bolts cheaper in the past? They're all unobtainium now.


Back on topic. If price is no objective, is it possible to build a compatible but virtually unbreakable bolt, like what Carol Lewis has claimed?

If that's yes, then do you really have to modify the extension, just to get a cost-effective bolt design?

[Pasta123]

While we're at it, might be a perfect time to bring out what Chicom is doing:


I wonder what's everyone's take on the BCG design. I'm skeptical, though.

to summarize:
1. a complete retaining pin mechanism vs. standard cotter pin.
2. fixed ejector.
3. extractor with dual oblique springs.
4. 4 lug design.
5. a lever to prevent cam pin from scratching the upper ("anti-pre-engagement").

[Uncas47]

Thrym makes a battery case for two CR 123s, I keep one with a Colt bolt with firing pin inserted, cam pin and retaining pin. It's a tidy lil pkg that stows easily. It will probably be easier to just grab the Glock if a bolt shits the bed.

[constructor]

Speaking of price, Are all the decent enhanced bolts cheaper in the past? They're all unobtainium now.


Back on topic. If price is no objective, is it possible to build a compatible but virtually unbreakable bolt, like what Carol Lewis has claimed?

If that's yes, then do you really have to modify the extension, just to get a cost-effective bolt design?

You would need to look at the yield strength and charpy value of every possible alloy and all possible heat treats for those alloys to figure out which will give you the most strength without getting brittle.
One of the few companies that made enhanced bolts made the first few batches too hard, like many they thought the harder the stronger. The bolts chipped around the cam pin hole and corners of the lugs.
If you are only talking about 5.56 bolts then yes, you could make bolts that would last many thousand rounds without too much effort. We were a small shop but machined apx 300 bolts a week for almost 10 years and still have had none break or none reported.

[prepare]

Wasn't the premature bolt breakage issue identified shortly after the GWOT started as a heat treat issue?

Who is still experiencing short bolt life?