NEW SPR TROUBLE ON FIRST RANGE TRIP. UPDATE IN OP.

[TomMcC]

I guess the 15/16 just missed the boat on the whole NM specs thing.

[ScottsBad]

Last I checked the Colt extractor spring was the only properly engineered upgrade. Worth sourcing if you feel the need, but you really shouldn’t “need” it on a rifle.

This sounds like excrement to me. There are thousands of BCM rifles and uppers, not too mention BCM BCGs out there. I've never heard a complain about BCM extractors, or extractor springs.

I think you should offer up some engineering based explanations that we can verify or at least consider. Perhaps an article or white paper. Or are you just barking something that sounds like, "only Colt has the TDP" therefore, only Colt can make them to spec. Because I've never heard that that Colt is the only company that engineers them properly. In fact, I've read that the Sprinco extractor springs are superior to Colt's copper colored springs.
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Frankly, it doesn't matter to me, that much, I just use Sprinco or BCM. They just work without a doughnut, very reliably, and that's all I care about. It just bugs me when people make statements unless they can explain the reasoning.

[ScottsBad]

It’s not about who makes the strongest, it’s about not exceeding spring engineering stress limits. Above those limits spring life can go down significantly.

There is no room in the space available to put the spring you would want in there. The Colt is basically as much as you can fit within that stress limit.

That’s about the extent of what I got from knowledgeable sources, I have not run the numbers myself.

That is very thin and really doesn't address the question.

[ScottsBad]

Spring calculations are not that complicated. You are welcome to get a engineer to tell you how spring stress works if you don’t believe me.

You can do the stress calculations yourself, there are free calculators available online. You only need a few measurements off the spring.

That's ridiculous. Materials, heat treatment, dimensions, design goals, spring manufacturing all have something to do with the compression strength, MTBF/spring fatigue, loss of spring strength.... Stress calculations are going to be pretty damn dependent on materials, design, manufacture specifics.

Maybe you can get some real information, I'd be happy to hear why your statement is true.

[ScottsBad]

As I said, it’s not hard to do yourself. Somebody I trust enough to properly measure a spring had a few different ones to work with. This was years ago and I don’t recall what specific “extra power” springs he had.

That info has kept me running, without any problems, a Colt gold or standard rifle with o-ring. I have never seen a viton o-ring come apart and I suspect it’s standard rubber ones that do but I replace them regularly anyway.

I’m not looking to disparage anyone’s favorite manufacturer, just passing on some knowledge I picked up that at least some of the “extra power” springs are not properly engineered.

Its not about favorite manufacturer, its about truth. I'd be happy to know that Colt extractor springs are the "end all" of extractor springs. If it was true, I'd buy a few for backup. I think I have one right now, so I'd buy more. But for the price they are ridiculous. I could change out my BCM or Sprinco extractor springs twice as often or more for the cost of a Colt spring at Brownnell's.

[Hohn]

It just bugs me when people make statements unless they can explain the reasoning.

Likewise, which is why I challenged it as diplomatically as knew to.

[Todd.K]

Stress calculations are going to be pretty damn dependent on materials, design, manufacture specifics.

That info is exactly what you put in the calculator. And you would know you just need a few measurements off the spring, and the material if you bothered to look at one.

The stress should not exceed a certain percentage of the tensile strength, and this is something the calculator will spit out. It’s not rocket science.

I gave the “buy a Glock and 6920" answer based on my basic understanding of springs and info I got from a reputable source back when I was in the industry. I would not run an "extra power" spring without checking the stress because of what I learned. I also have not found the need to run any yet.

Colt designed their own spring that was an M4 upgrade, but it stopped short of many of the aftermarket, and Crane used an o-ring when they needed more tension for the Mk18.

[Straight Shooter]

Gentlemen- God bless yall for the info & questions & back & forth so far. NO ONE has yet crossed the line, but PLEASE, lets continue to be civil & LEARN from one another-THANK YOU ALL for your help.
QUESTION: I had a thought hit me yesterday...since the NM bcg is bigger & heavier, would an "extra power" recoil spring help in any way?
What about the Tubb RS? Or, any other yall might recommend? I did not see a EP RIFLE RS on the Sprinco page. Thoughts on this please.

[sinister]

I wouldn't add a stiffer spring. Yes, a stiffer spring will retard unlocking/extracting a little, but once your bolt group compresses and hits the end of the extension the spring is going to expand and slam that carrier forward faster, which may cause it to out-run your magazine spring trying to push cartridges up into the feedway.

I like Tubb flat springs.

[Straight Shooter]

I wouldn't add a stiffer spring. Yes, a stiffer spring will retard unlocking/extracting a little, but once your bolt group compresses and hits the end of the extension the spring is going to expand and slam that carrier forward faster, which may cause it to out-run your magazine spring trying to push cartridges up into the feedway.

I like Tubb flat springs.

THANK YOU.
After posting this- I saw the excellent thread here on springs. I liked the reviews of the 42 coil Tubb spring, and was considerng it already when I saw your fast response. Should I try the 36 or 42?