Educate me-Flat wire vs round spring technical data...

[tom12.7]

Just to add some clarity about the initial shock loading posted above. It was more focused on the beginning of the action cycle stacking coils closer together compared to a regular Colt action spring on the buffer end of the spring. Less emphasis on the resonance aspect of shock loading.

[Goldorak]

Resurrecting this: can someone translate tom12.7 and crosseyedshooter's conclusions into plain English? All I understood was that they have some advantages, but also some downsides. Which are stronger/more important/"better"? Tom12.7 was talking about the early days. How about now?
What's the verdict? Do you recommend them? To be avoided?

[tom12.7]

I can add some more details later, I'm short on time now.
The spring has changed somewhat, more for the better though. To get any value from it, the system needs low drag and reduced cyclic speed for the bolt unlocking sequence. Low drag meaning meaning friction from the action system. Reduced cyclic speed for the bolt unlocking sequence that ends up meaning higher reciprocating mass requirements, details later. You can't really do it in a carbine action as well as in a rifle like or A5 type action, less active coils mostly for their respective spring. Even with a A5H4, do not push the .308 flat wire action spring change out further than a standard carbine spring for your schedule. I would avoid the .308 flat wire in the A5H2 or lighter systems. It does work with the A5H4 better than the A5H3. You can also easily find yourself requiring specific gas porting for the A5H4 Tubb flat wire if your drive is to use that action system, it can be more forgiving to increase an operational span or usage. Excess drag from this can become very evident depending on many things or a stack up of RE interior bore and finish, offset or angular RE alignment (many don't know how bad this can be), etc..
More later if there's any interest.
It is far easier overall to gas a system for the Colt spring A5H2 for most. If your combination suits it though, you can increase your operational span with the .308 Tubb flat wire A5 combination, but don't expect it to last beyond your standard carbine action spring.

[Motivated1]

I can add some more details later, I'm short on time now.
The spring has changed somewhat, more for the better though. To get any value from it, the system needs low drag and reduced cyclic speed for the bolt unlocking sequence. Low drag meaning meaning friction from the action system. Reduced cyclic speed for the bolt unlocking sequence that ends up meaning higher reciprocating mass requirements, details later. You can't really do it in a carbine action as well as in a rifle like or A5 type action, less active coils mostly for their respective spring. Even with a A5H4, do not push the .308 flat wire action spring change out further than a standard carbine spring for your schedule. I would avoid the .308 flat wire in the A5H2 or lighter systems. It does work with the A5H4 better than the A5H3. You can also easily find yourself requiring specific gas porting for the A5H4 Tubb flat wire if your drive is to use that action system, it can be more forgiving to increase an operational span or usage. Excess drag from this can become very evident depending on many things or a stack up of RE interior bore and finish, offset or angular RE alignment (many don't know how bad this can be), etc..
More later if there's any interest.
It is far easier overall to gas a system for the Colt spring A5H2 for most. If your combination suits it though, you can increase your operational span with the .308 Tubb flat wire A5 combination, but don't expect it to last beyond your standard carbine action spring.

There's a lot there! I'll start with the ' angular RE alignment', extrapolate that, please.

[Goldorak]

Thanks Tom12.7! Lots of good info here. Please, expand as much as you can, so we can all benefit from your knowledge! Especially about "higher reciprocating mass requirements, details later."

I'm definitely looking at A5 and rifle rec extensions with 308 flat wire. The carbine one does not look long enough for such a long spring anyway.
Bigger L1 and not too big L2 is what makes the 308 flat wire appealing for my (slightly) overgassed rifles.

[crosseyedshooter]

In my simple mind, and generally speaking, flat wire spring geometry is stressed more than round wire springs. The benefit of flat wire springs is to store more energy in a limited space (buffer tube) as compared to a round wire spring due to higher coil count (so-called 308 spring) in the same stack height (carbine extension and buffer). There's no free lunch here.

In an overgassed rifle, the first and best solution is to correct the gas port diameter or throttle the gas with a restrictor or adjustable gas block. However, the discussion here is about playing with the other factors, reciprocating mass, stored spring energy, etc. The L1(F1) and L2(F2) are not values that directly relate to solving your overgassed problem. You simply want a spring that can store more energy so the buffer has minimal impact at the end of the receiver. Whether you achieve that with a stiffer spring (Sprinco) or a longer spring (flatwire) depends on the tradeoffs you're willing to make.

Interpreting tom12.7's post, the flatwire spring longevity will benefit from full weight carrier and heaviest buffers, smooth receiver tube and minimal carrier tilt, all to reduce the "shock" to the flatwire spring. Sudden hangups and abrupt changes in friction surfaces, initial bolt acceleration, should be minimized when using the flatwire spring.

If looking to improve from a carbine system, something like the A5 or rifle extension with Sprinco spring is already a best of both worlds compromise by using a longer AND stiffer round wire spring with ability to increase buffer weight due to longer buffer body.

[WS6]

So maybe we start with how the product has changed since it first entered the market?
When the spring was first introduced to me, when it was relatively new, I decided to test some out. At the time I was informed that for 5.56 there was a carbine action spring, that could work on some 5.56 rifle actions. A .308 spring that worked with AR-15 carbine buffers with the 3/4"ish extended carbine RE for .308, rifle actions in .308, and some 5.56 rifles.
I already had a low friction set up to test spring loadings from an earlier project. Very simple with a load cell, force screw, and 3 polished rods (to simulate the RE diameter). The testing on the fixture looked great, some more L1 with very similar L2 with the carbine spring. I tried the spring in many known good platforms, the results ended up being erratic. After some more testing, I was looking at what appeared to be friction dragging the action down. I altered my original fixture so that I could check for drag by using a pusher rod down the barrel of an assembled rifle minus the bolt so that the pusher rod was seated to the carrier to test in compression and rebound. The findings were that there could be much more drag in some systems than others. Additional testing was done, the flat wire could add friction that normally wouldn't be there in a conventional spring. There was combinations that worked well, but the flat wire spring was less tolerant to combinations of factors, offset and angular misalignment for the RE, RE interior finish, etc.. There was a coating on the springs, but no amount cycling could make a marked improvement in some with issues, others seemed fine.
A similar test was done slightly later on with the longer version of the spring in rifle actions. Their marketing indicated that cutting coils to trim the spring could be used for tuning. Personally, I'm not a fan of an end user attempting this. I very much believe that springs for this need to be properly closed and ground square, anything else adds an angle to that portion of the spring. That makes more drag on a regular spring, adding that to a flat wire spring adds insult to injury. Cutting the springs down could hurt L2 tensions to the point that the safety margin diminished for stripping the round out of the magazine to chamber. Masking friction issues by reducing the work required to cycle the action isn't a good place to be.
There were combinations that seemed to work well enough, so more testing was done. When the drag was low, the springs showed benefits. Around this time, I was able to get with an engineer that actually worked on springs. He wasn't fast about getting back with me, it took him over a year. During that time I continued with the combinations that seemed to work well and relegated the others back to normal springs.
In some of my "good" flat wire combinations, issues came up. Symptoms started as erratic forms of function. Upon removing the springs, it was evident that some coils towards the buffer became kinked. Not long after, those springs would break. I wouldn't run a broken spring, even if there was some function, so those combinations were out.
A few others, mostly suppressed guns started to show signs of corrosion on portions of the spring.
Around this time, my spring engineer guy got back with me. When he told me the stress level range compared to a normal spring, I understood that the spring had 50% more stress than a conventional one. I still had some combinations that seemed to work well, so I continued to test. The springs with rust would fail fast and would break in multiple locations. During that same timeframe, I had the opportunity to test some cut away guns on camera. I was not and am not opposed to the concept of the L1 and L2 tensions of the flat spring, more of the offering's execution of that. What was found in the camera findings was how tightly the springs coils could stack together quickly during the action sequence towards the buffer end. The shock loading of the spring during initial movement was shown to my spring engineer with different amounts of gassed uppers using different buffer masses. The lower mass shock loaded more than than the higher mass options and he really questioned the L1 loading with the action at higher velocities.
At the end with the issues of drag, breakage, rust, shock loading, etc.. I gave up on how the spring was done, not the concept of the increased L1 with similar L2 for this system. Pneumatic systems showed that years prior, but carrying an air tank with hoses is not practical. While in typing, the process explained may seem exhaustive, but it was not out of my normal during that timeframe doing what I was doing.
This is by no means to condemn or discourage others from trying the product, as their execution of this has improved by a great deal at this time. It's not a jack of all trades by now, but a master of some. The product has improved in time, and I am glad to see that. There are some other issues that could be addressed, but it is good to see how the product has improved over time.
More to follow if interested.

I filmed rifles in slow motion suppressed and unsuppressed using all manner of springs. I found the Tubb Flatwire springs to "feel" good to me, the shooter, but they were very erratic in ejection performance, which leads me to believe carrier velocity was also erratic, and they also caused much more "muzzle dip" than any other combination I tried, upon return to battery.

[Goldorak]

Crosseyedshooter, thanks for your input!

You say: "Whether you achieve that with a stiffer spring (Sprinco) or a longer spring (flatwire) depends on the tradeoffs you're willing to make." Can you elaborate on the tradeoffs for each?

Also, did I understand correctly from your last sentence that a Sprinco green spring is "better"?

[crosseyedshooter]

Crosseyedshooter, thanks for your input!

You say: "Whether you achieve that with a stiffer spring (Sprinco) or a longer spring (flatwire) depends on the tradeoffs you're willing to make." Can you elaborate on the tradeoffs for each?

I think tom12.7’s and my posts already did. Flatwire has flatter F1-F2 slope and higher energy storage for a given space but is less consistent, causes more friction, is susceptible to shock loading and can fail from over stress.

Roundwire needs higher k and steeper F1-F2 slope to store more energy in the same space, has less friction and stress but will have more “ramping up” feel as it compresses.

Also, did I understand correctly from your last sentence that a Sprinco green spring is "better"?

What characteristic do you consider “better”?

[Goldorak]

"Better" means more advantages and less downsides. Just from the post above:
Flatwire has 2 plusses and 4 minusses.
Roundwire has only one minus. Still trying to figure out what "needs higher k and steeper F1-F2 slope to store more energy in the same space" means for a rifle. But it sounds less dramatic than the disadvantages of the flatwire.

There's no free lunch, I get it. So, I'm looking at both the number of +s/-s and the perceived importance. And struggling mightily... lol