dellet
Gold $$ Contributor
There is also a force that is only applied at the exit of the bullet, how does that factor in?
Building a 9mm AR w/16" barrel - Bullet Velocity Question
- Thread starter MoneyWaster
- Start date
There is?
I can't see any physics to explain one.
dellet
Gold $$ Contributor
There is in my simple mind.
Don't know the physics or I would not have asked, I can give an example of why I think the way I do.
Pipe with fixed cap on one end with an air valve installed. Fit the open end with a pressure fit cap.
When you add enough air pressure to overcome the the press fit cap, both ends move in opposite directions.
Why would a bullet exiting a barrel be any different, both are a release of pressure?
Even on the Ring, that equation balances upon exit
..... nor Louis Wu nor the Protectors can produce force outside the equation, ain't no different physics anywhere in the multiverse altho The Hindmost and his fellow puppeteer hoppers come close..... they had us perplexed there for a while....I played with a Slaver Stasis Field there for a while, trying to catch bullets unmarked but D'ANG!!! When I shut the field off and reached for them they disappeared.....
Now where did I put my piece of GP hull material?
Good question, here's the answer....
The pressured up pipe is "the cartridge" just setting there full of potential energy in the form of compressed air.
The rifle cartridge is also just setting there full of potential energy stored as solid fuel.
You open the pipe (ie blow the cap off) and when the cap starts to move an acceleration BEGINS, the pipe and cap fly off in different directions. The bullet is the pipe, the barrel is the cap. And YES, there's a small push remaining for a few inches while the pieces are still within the expanding gas cloud but only because the acceleration has had so little time to act on the two pieces. AND, because the gas cloud hasn't achieved much speed and direction (velocity)
The rifle (and bullet) started accelerating back inside the gun, when "the cap blew off" and by the time the gases exit there's no appreciable "back pressure" to effect the firearm because the gasses themselves ALSO have a velocity.....away from the muzzle. For them to reach back and slap the muzzle would be like you riding the front bumper of a car, car STOPS and you fly off but do a quickie spinaround-reachback and SLAP the car as you leave. You can't, you can only flail.
When fireforming rifle brass using pistol/shotgun powder (NO BULLET!) one can get some serious blast effects, maybe knock the head off a dandelion at 10ft from the muzzle, but recoil is negligible, and generated ONLY inside the gun. Again, the gas cloud is moving forward so fast there's no "backpressure" on the muzzle.
It's a bad analogy because the release of pressure is an entirely different thing in each case.
In your improvised air gun the projectile is stuck, you slowly increase the pressure until it overcomes the sticking force and yes, then the projectile moves. That is a very inefficient 'gun' because there is practically no distance for acceleration to build up.
A firearm just doesn't work in that way. The explosion creates a violent force all in its own, accelerating the freely moving bullet forward. The only thing special that happens at the muzzle is the gas expands into a sphere thus no longer pushing on the bullet in any practical way. The release of pressure is the END of thrust and recoil that began in the chamber.
Look at a bow. We draw the string back, storing energy. We release the energy(equivalent to pressure) and the bow starts accelerating the arrow. When the arrow leaves the string acceleration stops and the arrow is in free flight.
Even on the Ring, that equation balances upon exit
I played with a Slaver Stasis Field there for a while, trying to catch bullets unmarked but D'ANG!!! When I shut the field off and reached for them they disappeared.....
Now where did I put my piece of GP hull material?
You're pretty clever for a monkey.
And FUNNY..... don't forget funny! That line about a piece of GP hull is friggin' PRICEless,
to seven or nine people
in history
dellet
Gold $$ Contributor
The other special thing that happens at the muzzle, is that the gasses accelerate once the bullet leaves the bore.
Why does the weight and volume of those accelerating gasses act differently coming out of a barrel, pushing against the breech than gasses accelerating and leaving from any other chamber?
Why does the weight and volume of those accelerating gasses act differently coming out of a barrel, pushing against the breech than gasses accelerating and leaving from any other chamber?
It's like a balloon popping.
If you blow up a balloon and let go, it's a gun. It's a rocket. A jet-propelled flying mo'chine accelerating about the space......
Until it hits a pin....
'POP!'
Now, those escaping gases going every direction ARE ACCELERATING, just like the gases that 'POP' from the gun muzzle but the whole "flying about the room" action.....stops.
The accelerating gases essentially act against each other spherically, or cancel.......except that there's still a stream of ejecta impinging the one side of the expanding gas ball, the gun side. It's all a matter of perspective but there's no real force or kick imparted to the firearm anymore. Yeahh, there's a tiny force that could swirl back and maybe drift a leaf or a feather backward but that's due to gas laws
Too bad this post turned into a I'm smarter than you one as usual.
To the op, have fun with the pcc, I bought 3 of them over the fall and winter and dumped over 10K rds through them. Thanks to an indoor range here in town, had fun all winter as I was gut full of LR shooting.
The indoor has pistol leagues all winter, and each week a new USPSA coarse is set up on one side of the building. I took my 11 yr old Godson(a runt) up each week and shooting a 8" Sig mpx with a brace his times and scores outdid over 65% of adult shooters. And the looks and comments he or we received were priceless, from that is great, to that is just a little much. The funny part was, w/o taking a 4 hour class, he cannot shoot a pistol there, but a 40rd mag was doable with a pcc.
To the op, have fun with the pcc, I bought 3 of them over the fall and winter and dumped over 10K rds through them. Thanks to an indoor range here in town, had fun all winter as I was gut full of LR shooting.
The indoor has pistol leagues all winter, and each week a new USPSA coarse is set up on one side of the building. I took my 11 yr old Godson(a runt) up each week and shooting a 8" Sig mpx with a brace his times and scores outdid over 65% of adult shooters. And the looks and comments he or we received were priceless, from that is great, to that is just a little much. The funny part was, w/o taking a 4 hour class, he cannot shoot a pistol there, but a 40rd mag was doable with a pcc.
No, it's really not, I take the path of least resistance, life really is simple.
forging onward
Milo
Yes - The Recoil from an AR9 can feel stronger then an AR15 (.223/5.56). Everyone else has provided a detailed answer... I think what you are noticing is pushing a heavier projectile and also a direct blowback system in the AR9. You can look to use a muzzle break to offset some of the less favorable aspects (muzzle jump/rise, etc.) and it may also reduce some of the felt recoil.
Yes - velocity of 9mm bullet can be lower when fired through an AR9 (16" barrel) as compared to same cartridge fired through a pistol....it just depends upon the initial load (plinking load vs. +P) Pistol powder is very fast burn rate and must accelerate projectile to speed within a few inches (4"-5" for most pistol barrels). The muzzle velocity does continue to increase beyond 5", but let's call it by 8"-10" (guesstimate) it achieves 100% powder burn. From this point forward the bullet is now slowing down as result of barrel friction.
Yes - velocity of 9mm bullet can be lower when fired through an AR9 (16" barrel) as compared to same cartridge fired through a pistol....it just depends upon the initial load (plinking load vs. +P) Pistol powder is very fast burn rate and must accelerate projectile to speed within a few inches (4"-5" for most pistol barrels). The muzzle velocity does continue to increase beyond 5", but let's call it by 8"-10" (guesstimate) it achieves 100% powder burn. From this point forward the bullet is now slowing down as result of barrel friction.
Based on my experience with an AR platform pistol caliber carbine, I think you will be underwhelmed when you actually have one. If you are looking for economical to shoot, lightweight, and fun - I suggest building a legal SBR using a Ruger Charger in .22 or 9mm. Then, to double your fun, suppress it.
The only 2 loads I've chronographed in my 14.5" Faxon barrel with intergral flash hider were 147gr W-W @ 1117 fps and 115gr W-W @ 1393fps.
Before going down the AR-9 rabbit hole, I gathered as much information as I could about the behavior of the average commercial 9mm characteristics.
Not wanting to bother with an SBR but still wanting to take full advantage of the 9mm cartridge, led me to decide on a 10.5" pistol build. Using a standard AR-15 lower, a completed upper assembly, and Endomag inserts to feed it, resulted in a toy that is controlled exactly like any other AR, including last round bolt hold open.
It is accurate within reason out to 100 yards and has a fairly flat trajectory when sighted in at that distance.
This configuration has proven to be ideal for something appropriate for home defense, with a little more firepower than the typical handgun.
Mine is equipped with a red dot that makes target acquisition fast and easy, and the added versatility of a laser for those special occasions.
Be sure to select the appropriate spring(usually .308) and longer & heavier buffer to reduce the risk of OOB firing(ask me how I know). 9mm is blowback operated and will have a heavier recoil than 5.56/.223. I would also caution against using a polymer lower for any pistol caliber build other than perhaps a dedicated .22LR.
Not wanting to bother with an SBR but still wanting to take full advantage of the 9mm cartridge, led me to decide on a 10.5" pistol build. Using a standard AR-15 lower, a completed upper assembly, and Endomag inserts to feed it, resulted in a toy that is controlled exactly like any other AR, including last round bolt hold open.
It is accurate within reason out to 100 yards and has a fairly flat trajectory when sighted in at that distance.
This configuration has proven to be ideal for something appropriate for home defense, with a little more firepower than the typical handgun.
Mine is equipped with a red dot that makes target acquisition fast and easy, and the added versatility of a laser for those special occasions.
Be sure to select the appropriate spring(usually .308) and longer & heavier buffer to reduce the risk of OOB firing(ask me how I know). 9mm is blowback operated and will have a heavier recoil than 5.56/.223. I would also caution against using a polymer lower for any pistol caliber build other than perhaps a dedicated .22LR.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.