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Gas timing ?


Candid

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1 minute ago, 98Z5V said:

Tell me why you think that about me - you formed that opinion somehow? That's not the case about me at all, and if you knew me, you're DEFINITELY know better.

I like shooting long distance, more than anything else, and I do it often, and I don't do it poorly. 

If you're here to "ask why about why" - then you need to put in your own research to satisfy your own goals in that.  We don't have any guess about your "why is why" - and only you can figure that out.

Be sure to post up your results, though.  :thumbup:

It was an abstract juxtaposition without any basis.  I know nothing of you but your hundreds of contributions to this forum.

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4 minutes ago, 98Z5V said:

In that reference, speed of sound doesn't have anything to do with it, not in the least.  Speed of sound is 330m/sec.  Projectiles travel alot faster than that, once fired.  "Flame front velocity" all depends on the weight of the projectile, and the powder used, as to how fast that powder reacts to it's ignition, and begins pushing that projectile out of the case... 

Speed of sound is 330m/s, at standard temperature and pressure. It changes with temperature, and; pressure as well. Your ears are obviously useless inside the barrel, but physics still applies.

What I was trying to figure out when I first read the initial question; "is this actually a plasma, and not a gas at those pressures"? That changes the game 100% (and from your deduction that "it's all pressure" I still think that's entirely possible).

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9 minutes ago, 98Z5V said:

In that reference, speed of sound doesn't have anything to do with it, not in the least.  Speed of sound is 330m/sec.  Projectiles travel alot faster than that, once fired.  "Flame front velocity" all depends on the weight of the projectile, and the powder used, as to how fast that powder reacts to it's ignition, and begins pushing that projectile out of the case... 

Speed of sound is 330m/sec in what medium?  Gaps....

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2 minutes ago, Candid said:

Copper compression Units are the standard for chamber pressure measurement.  That is a difficult concept to get ones head around.  😉

Internal ballistics is exactly the topic. There have been some great pieces written on the topic.  but.. tedious reading for anyone not inclined.  Gas actuated mechanisms have added an additional level of complexity and intrigue. 

 

The referenced piece above suggests that the gas speed is 5X the MV at the muzzle.  Must be greater yet at the gas port.  But..  It meets with some resistance soon enough.  A wall of hot spent gasses pressing on a fixed still air volume.   Hmm  Interesting effects to consider.

 

 

Read this.  I've read it over and over, and every time I finish, I start it again.  When you have questions about any information in here, make sure you contact Brian Litz, and not me.  He wrote it, and he's probably better at answering your questions than I would be - about his work.

 

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2 minutes ago, Lane said:

Speed of sound is 330m/s, at standard temperature and pressure. It changes with temperature, and; pressure as well. Your ears are obviously useless inside the barrel, but physics still applies.

What I was trying to figure out when I first read the initial question; "is this actually a plasma, and not a gas at those pressures"? That changes the game 100% (and from your deduction that "it's all pressure" I still think that's entirely possible).

No Pressure change is instantaneous.  Just as no motion is instantaneous.    That is the topic. 

The effects and the actions must work together. 

 

The reference offered shows a great diversity of pressures at the gas port associated with four common barrel configurations.  They all seem to be workable.  I find that interesting.

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3 minutes ago, Lane said:

Speed of sound is 330m/s, at standard temperature and pressure. It changes with temperature, and; pressure as well.

 

 

2 minutes ago, Candid said:

Speed of sound is 330m/sec in what medium?  Gaps....

Now, you guys are talking about Density Altitude...   But you didn't know that before now - unless you're just asking questions to cause issues.

Density Altitude will affect the speed of sound, speed of your projectiles, and small airplanes in flight - at altitude.  Density Altitude is what they have to calculate, to make sure they have enough gas to fly where they're going to - and not crash beforehand.  Read the book.  Ask questions to the author, and not me.  You'll understand alot more after you read it.  Or, not.

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4 minutes ago, 98Z5V said:

Read this.  I've read it over and over, and every time I finish, I start it again.  When you have questions about any information in here, make sure you contact Brian Litz, and not me.  He wrote it, and he's probably better at answering your questions than I would be - about his work.

 

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Is there a section on internal ballistics?  It appears to be a good read on external ballistics if the title is "Long range".

I live in the Eastern hardwood forest.  100 meters is about as far as one can see through the woods.

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12 minutes ago, Candid said:

The referenced piece above suggests that the gas speed is 5X the MV at the muzzle.  Must be greater yet at the gas port.

This is about what I expected intuitively. One could load blanks, and super light projectiles to mess around with this. Not really sure off hand what kind of recording equipment would be useful though. Really depends what you are most curious about in this situation. 

Design an experiment. Execute. Talk about it. For some people, that's daily life... Don't be afraid to be curious. Try to focus your questions.

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2 minutes ago, Candid said:

Is there a section on internal ballistics?  It appears to be a good read on external ballistics if the title is "Long range".

I live in the Eastern hardwood forest.  100 meters is about as far as one can see through the woods.

Read the book, or just keep asking questions.  It's all up to you at this point.  Risk it.  Show me how brave you are.

If you only shoot 100 yards, then what is your goal?

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2 minutes ago, 98Z5V said:

 

Now, you guys are talking about Density Altitude...   But you didn't know that before now - unless you're just asking questions to cause issues.

Density Altitude will affect the speed of sound, speed of your projectiles, and small airplanes in flight - at altitude.  Density Altitude is what they have to calculate, to make sure they have enough gas to fly where they're going to - and not crash beforehand.  Read the book.  Ask questions to the author, and not me.  You'll understand alot more after you read it.  Or, not.

Density altitude applies to external ballistics in fire arms.    Do you need a copy of my FAA Repairman's license or my flight log?    It's been some years since I've exercised either,  but BTGTTS.

Hot High and Humid

The topic at hand is HOT

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4 minutes ago, Lane said:

This is about what I expected intuitively. One could load blanks, and super light projectiles to mess around with this. Not really sure off hand what kind of recording equipment would be useful though. Really depends what you are most curious about in this situation. 

Design an experiment. Execute. Talk about it. For some people, that's daily life... Don't be afraid to be curious. Try to focus your questions.

I have played with 5 grain "cut lead" projectiles from several air rifles.  Over the chrony they go nearly 1400fps.  Crack! 

But they don't go very far,  and don't strike anywhere near where they are pointed.

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1 minute ago, 98Z5V said:

I live in the Eastern hardwood forest.  100 meters is about as far as one can see through the woods.

This is what broke me too. Distance shooting would be a dream. It's trivial to build a rifle that's accurate for 100 meters (hunting). Some of us rarely get a chance to reach out further.

Once that sinks in; it's easy to become curious about the other nuances at play. It's sort of the best one can do in terms of preparing for that "one day" when they'll be allowed to shoot at long range. 

But at the surface. It sure would be "neat" to have a calculator for the gas system vs. recoil. Spring constants are VERY easy to calculate (had to do that in university physics labs). Those other variables could be determined easily enough with some data collection (and I mean A LOT of data collection)... 

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1 minute ago, Candid said:

Smooth cycling, minimal disturbance, one hole, and two hours of pleasant range time....

Well you might not care as much about internal ballistics as you think you do. 

I've been pointed here in the past. But read up on OBT. Let me know what you think of that theory... That should solve most of your problems besides the smooth cycling. 

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2 minutes ago, Candid said:

Smooth cycling, minimal disturbance, one hole, and two hours of pleasant range time....

You should probably contact the author of this article, and ask him your questions.  He might be the only one that will satisfy you...

What you're asking about has nothing to do with "gas timing" - as you've now stated it.  Read this - then contact THAT author...   :thumbup:

https://precisionrifleblog.com/2013/10/18/secrets-of-the-houston-warehouse-lessons-in-extreme-rifle-accuracy/

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1 minute ago, Lane said:

This is what broke me too. Distance shooting would be a dream. It's trivial to build a rifle that's accurate for 100 meters (hunting). Some of us rarely get a chance to reach out further.

Once that sinks in; it's easy to become curious about the other nuances at play. It's sort of the best one can do in terms of preparing for that "one day" when they'll be allowed to shoot at long range. 

But at the surface. It sure would be "neat" to have a calculator for the gas system vs. recoil. Spring constants are VERY easy to calculate (had to do that in university physics labs). Those other variables could be determined easily enough with some data collection (and I mean A LOT of data collection)... 

Well said!

 

With that,  I put a new spring in the SKS about a year after picking it up,  What a difference in cycle smoothness.   That bolt carrier was slamming with the original spring.  Not a costly change,  and what a useful result!  If only it would shoot straight 😉  MOD  is best one can ask.

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3 minutes ago, 98Z5V said:
9 minutes ago, Candid said:

Do you need a copy of my FAA Repairman's license or my flight log?  

Don't need a copy of either, and I don't care about them. 

Wana see my FAA license too? LOL. I think we need a new waterboarding for science thread.

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1 minute ago, 98Z5V said:

You should probably contact the author of this article, and ask him your questions.  He might be the only one that will satisfy you...

What you're asking about has nothing to do with "gas timing" - as you've now stated it.  Read this - then contact THAT author...   :thumbup:

https://precisionrifleblog.com/2013/10/18/secrets-of-the-houston-warehouse-lessons-in-extreme-rifle-accuracy/

No,  That is really not the interest.  That entire obsession is way to much tension.

I don't "think" the author has much interest in gas actuated autoloaders.

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2 minutes ago, 98Z5V said:

Read this

YEAH!!!! That one too. You can read about O.B.T. after that. You'll need both.

In all seriousness. There is a TON of research beyond that; but both of those are a super jumping off point.

Frankly; I'm suspicious about the barrel length variable in OBT. But the general theory is absolutely correct (pretty sure the basic formula is still wrong though). 

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4 minutes ago, Candid said:

Yes,  I think you have missed the effect of gas pressure propagation as a function of temperature

Not at all - that's Density Altitude, and the effects it has on firing guns (bolt, gas, whatever) at different temps and altitudes and pressures...  I've posted about this, and the differences I'VE seen in my own gun's performances...   50 degrees to 113 degrees.  I posted about this recently, and the differences I saw at 850 yards, between those two temps, same load.  8.5 mils of drop at 850 yards at 50 degrees, 7.0 mils of drop at 850 yards at 113 degrees.   This was a recent thread that I posted...

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