Gas timing ?

[98Z5V]

Scientific Research on the differences between a 16" barreled AR15 chambered in 5.56mm, one with a Carbine Gas System, and one with a Midlength Gas System, will tell you what you want to know.

Now, be advised - we HERE have not DONE those tests - but they are out there on the Wild Wild Web. Results, too. All the way down to real recoil in ft/lbs,  felt recoil, internal damage to the internal components over the long term, - ALL that.

Happy hunting.  I think that's the info that you're looking for. 

[Lane]

4 minutes ago, 98Z5V said:

^^^  Well done @Lane, compiling that info - I'm saving those links, man. 

I don't want to thank the wrong person. But @SimonSays was around back then. I can't find it in the search at the moment...

There's a LOT of good reads to add on. TONS of research from the turn of the previous century is GOLD. I wouldn't ONLY stick to modern literature. You'd all likely be shocked at how much we knew back in 1905-ish.

[Candid]

2 minutes ago, Lane said:

To be frank. You can measure that with a microphone attached to your gun. But yes. There is certainly some research in that area. Even a high speed video camera would do a lot (since it has synced audio too). There are plenty of slow motion youTube videos even.

Since there are so many variables (including part fit, and absolute friction (the sum of all those)); you're not going to get a perfect fit calculator. Too many other factors too. Bullet fit in the barrel (amount of blow by), twist, barrel profile, caliber, amount of blow by in the chamber as the cartridge seals), etc. etc etc. 

The good part is, the timing on the bolt side is so LATE in the process you can "hear it all" in your own gun. If you want to add and IMU (gyro/accelerometer) that could help if you had some mechanical issues too... 

But I still don't know what you don't know, or what you want to know.

I've attached strain gauges to actions during firing cycles and recorded the signal on an o-scope, as well as recorded the acoustic signature of a firing cycle  (bolt actions , not auto loaders)  but I have not the means to do all that I would desire.  Hence the quest for those who might have be curious and have had the required equipment at their disposal.

[Candid]

6 minutes ago, 98Z5V said:

Scientific Research on the differences between a 16" barreled AR15 chambered in 5.56mm, one with a Carbine Gas System, and one with a Midlength Gas System, will tell you what you want to know.

Now, be advised - we HERE have not DONE those tests - but they are out there on the Wild Wild Web. Results, too. All the way down to real recoil in ft/lbs,  felt recoil, internal damage to the internal components over the long term, - ALL that.

Happy hunting.  I think that's the info that you're looking for. 

So you are replying that you can not reference any particular literature,  but you feel a web search would return the information.

Great,  thanks!

[Lane]

Which one? It's really all a matter of what data you want. A triggered recording of all of the above would be quite simple. 

Where do you want a strain gauge? They can be placed almost anywhere. The standard measure is over the chamber to measure the pressure inside the cartridge. That's tough in an AR with the barrel nut in place. To modify your own gun you might need to replace that (break perfect timing), or use a sub-standard placement. They can also be placed on the upper, or the barrel; or even the lower.

Record the sound at the highest sample rate possible. Record the Gyro data from the barrel and acceleration data on the upper receiver. Where have I heard of this before? 

Anyway. A quick an dirty would be an old cell phone. Preferably the lightest weight model you can find. Don't know what kind of Go Pro has high speed video recording these days. But that would be a good start as well. 

Seriously. An audio recording from your Phone or with a Microphone attached to the lower would give you almost 100% of the data you care about up front. You can add more when you find a hole.

[Candid]

8 minutes ago, Lane said:

I don't want to thank the wrong person. But @SimonSays was around back then. I can't find it in the search at the moment...

There's a LOT of good reads to add on. TONS of research from the turn of the previous century is GOLD. I wouldn't ONLY stick to modern literature. You'd all likely be shocked at how much we knew back in 1905-ish.

Mann and Longridge have been very insightful

[Lane]

4 minutes ago, Candid said:

Great,  thanks!

Are you still nipping his fins? You better watch yourself. I'd rather not get the full weight of that gorilla. 

[Candid]

2 minutes ago, Lane said:

Which one? It's really all a matter of what data you want. A triggered recording of all of the above would be quite simple. 

Where do you want a strain gauge? They can be placed almost anywhere. The standard measure is over the chamber to measure the pressure inside the cartridge. That's tough in an AR with the barrel nut in place. To modify your own gun you might need to replace that (break perfect timing), or use a sub-standard placement. They can also be placed on the upper, or the barrel; or even the lower.

Record the sound at the highest sample rate possible. Record the Gyro data from the barrel and acceleration data on the upper receiver. Where have I heard of this before? 

Anyway. A quick an dirty would be an old cell phone. Preferably the lightest weight model you can find. Don't know what kind of Go Pro has high speed video recording these days. But that would be a good start as well. 

Seriously. An audio recording from your Phone or with a Microphone attached to the lower would give you almost 100% of the data you care about up front. You can add more when you find a hole.

My findings is that the s/n ratio of an acoustic signature left a lot of gaps.

[Lane]

Oh. So you overdrove the input. No problem at all. Use a different Mic. You'll certainly need adjust for the violence that happens inside and outside of a gun. The conductive mic on the lower is probably the starting point. Use negative gain.

[Lane]

Do you want a strain gauge to use as a mic to attach to your lower? Use the one, or a very similar one; that someone uses for the strain gauge on the chamber. You can collect audio data with any PC sound card, or tablet, or cell phone. If you have access to audio recording equipment it's a lot higher resolution.

But again; you don't care about more than ms resolution already, so regular CD quality or DAT is fine if that's all you get.

[Candid]

4 minutes ago, Lane said:

Are you still nipping his fins? You better watch yourself. I'd rather not get the full weight of that gorilla. 

As Antoine de  Saint Exupery wrote:  "Words are the source of all misunderstanding".

[Candid]

2 minutes ago, Lane said:

Do you want a strain gauge to use as a mic to attach to your lower? Use the one, or a very similar one; that someone uses for the strain gauge on the chamber. You can collect audio data with any PC sound card, or tablet, or cell phone. If you have access to audio recording equipment it's a lot higher resolution.

But again; you don't care about more than ms resolution already, so regular CD quality or DAT is fine if that's all you get.

equipment...  perhaps there is someone who has already done this.  How did Stoner come up with his design?  plagiarism?  I do not know.

[Lane]

There are people who have already done this. I'm quoting some other sources for sure. 

https://archive.org/details/RifleAccuracyFactsFullV1.0FirstFullScan

[Lane]

4 minutes ago, Candid said:

How did Stoner come up with his design?

Stoner broke some rules. At the time aluminum was NOT considered appropriate for firearms. There is a lot to know about that in particular. Have you ever machined 6061-T6? It's easy to make some "weird" stuff happen when it get's gummy. Yet his designs proved to stand the tests of time... I don't think I own any 6061 lowers, but they are available. 

I've never read anything about IP theft. Do you think he stole it?

[Lane]

13 minutes ago, Candid said:

As Antoine de  Saint Exupery wrote:  "Words are the source of all misunderstanding".

No poop. That's why we all chose our words carefully. If someone spends that much time with you; you better sit up straight and take notice. It doesn't happen every day.

[Lane]

I'm going to reiterate this. It all boils down to the bubba gump shrimp company of it all... Any old redneck can do this with a hammer and a lee loader.

You have to make a ladder load, shoot them till they hit the 0. Same hole.

[Radioactive]

Wtf? You guys were awfully patient. 

[Matt.Cross]

Wow, just wow...

 

ETA: On a somewhat related topic, does anyone have any data on the average heat, pressure, and duration of a gnat's fart? I'm pretty sure gnats farting in my face are what's causing my 100 yard group holes to be so ragged....

[MikedaddyH]

I fell down this rabbit hole in 2012 and found my way out in 2015 . I put together a spreadsheet with gas port sizes from different manufacturers in pistol, carbine, mid-length & rifle gas tubes. Did this in 3 calibers. 

Do your own research, enjoy !

[jtallen83]

2 hours ago, MikedaddyH said:

Do your own research, enjoy !

Ah man, come on a share a bit 😉

[Candid]

7 hours ago, Lane said:

Stoner broke some rules. At the time aluminum was NOT considered appropriate for firearms. There is a lot to know about that in particular. Have you ever machined 6061-T6? It's easy to make some "weird" stuff happen when it get's gummy. Yet his designs proved to stand the tests of time... I don't think I own any 6061 lowers, but they are available. 

I've never read anything about IP theft. Do you think he stole it?

I believe the most significant firearm design contribution attributed to Stoner's AR-10 was the use of gas expansion to act between the bolt and bolt carrier to effect the operation.  Not actually a direct impingement system.

It is gas operated piston stroked bolt group that sets the Stoner design apart.   It must have taken some study to work out the required gas volumes and timing.

Or,, perhaps there are other similar actions that I have not encountered.

Frames can be made from alternate materials .  I have a steel lower "kit" that I may get to some day.  and of course now we have the printed plastics..  And yes,  6061 is more gummy than 7075,  It offers greater corrosion resistance however.  7075 and 2024 suffer from intergranular corrosion if not protected.  It is the Zinc and copper in those alloys.

 

 

 

 

[DNP]

All I know, is every part of this lesson plan is too far above my pay grade. 

[Lane]

I found a reasonable discussion about the gas system. From the U.S. Army Aberdeen Research and Development Center Ballistic Research Laboratories. I haven't read it cover to cover; but it does appear to cover all of the math required to figure out those parameters. 

https://apps.dtic.mil/dtic/tr/fulltext/u2/704342.pdf

[DNP]

Crap. We forgot friction. That’s it, I’m turning in my MENSA card...

[DNP]

Next PSA with ejection issues should polish up the outside of the gas tube and see if the rifle cycles better.