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So when I shoot my savage axis .223 and I eject the shells. I can catch them in the air and there a little warm but not bad. When I shoot an AR15 and the brass flies out and touches my arm it burns like crazy. Why the big difference in temperature??? Is it just the brass not having time to disperse the heat into the metal of the rifle??? Why is The difference in temperature so dramatic.
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Never really though much about it. I would guess it has to do with the cyclic rate between a bolt action and an AR, the number of rounds you fire through your AR, the temperature of the chamber between the AR and a bolt gun, and the air temperature difference between the AR and bolt gun (bolt gun's bolt is open for much greater period of time than AR).
Theres probably already been an extensive government study on this.
But if not maybe there should be one lol.
Most AR's use gas impingement - the gas from the fired cartridge is siphoned off to cycle the bolt. That gas is hot (and some say dirty). This is one of the big selling points of gas piston designs - the bolt stays cooler (and possibly cleaner).
^ What Rick_W said. And yeah, gas piston ARs will stay much cleaner than direct impingement.
In you AR the case is ejected not long after the bullet has left the barrel leaving no time to cool down. In a bolt action the case sits in the chamber for a longer period of time allowing the temperature of the barrel to "Soak" out the heat much like a heat sink. It is my opinion that the DI gasses are not the cause of the higher temperature case.
I don't know, but I once had a .45 ACP case fly up, bounce off of a piece of wire screen separating the shooting lanes and land between my lower eye/upper cheek and sun/shooting glasses. Burned me good and, as I flinched, jumped, and swatted it away, it dang near caused me to point my pistol down the row of fellow shooters on the line. Don't know whether I actually did or not, and no one complained, but I was quite "shook" and upset with myself as I reflected on it later... it was a 1911. I could have easily killed someone had I touched the trigger.
I think Robinhood has it right. I had a .30-06 shell from a Garand bounce down the back of my pants (don't ask), and it was quite, quite hot compared to those ejected from my .30-06 Axis. Now, I never got Axis ejectees in such a tender place, but there was pretty clearly a difference.
Why you should never go to the range dressed as a plumber..........Quote:
Originally Posted by DrThunder88
Free balling is never recommended at the range ;)
You know, I got to thinking (which my wife says is always dangerous)...
While I think the gas blowing back into the bolt may have some contributing factor I think it may be minimal.
I shoot Cowboy Action Shooting - lever-action pistol caliber rifles. Big cases (.45 Colt) with small amounts of fast burning powder to shoot slow velocities will put a blister on you when it lands on open skin. Don't let it get trapped between skin and clothes! Some of these empty cases are still too hot to comfortably pick up bare handed after 30-45 seconds.
So - maybe it has more to do with the powder/powder weight used???
No, no, and no. ARs have a gas system, and that gas system is what works the action back and forth giving you an evil and terrorizing semi-automatic feature!! All that hot gas from the fired cartridge gets sent down the barrel...up the gas tap... then it 180's right back to your face... dumping all that hot gas in the action. That is why they get so dang hot. Don't forget to tie your shoe laces tight! Happy shootin'
I have no idea what your shoelaces comment is supposed to mean...Quote:
Originally Posted by CrAzYLoCaL
The gas system was my first thought, too - see post #4.
But that doesn't explain hot brass from lever-action rifles.
If your shoe laces aren't tight brass could fall in there and burn your feet!
Some calibers have more bang than others.. more powder more heat. Some cases are thinner than others. There's so many different factors, so try not to split any hairs here. But back to ARs, they run hotter because of their design obviously, and that gas being dumped into the upper is constantly heating up the rounds in the magazine, inherently making every round hotter to begin with, before firing. Savi?
Cowboy boots don't have laces...:cool:Quote:
Originally Posted by CrAzYLoCaL
No savi.Quote:
Originally Posted by CrAzYLoCaL
By your explanation the top round in the magazine is getting heat soaked with every shot fired. I call BS on this. I've fired many rounds out of AR's and have done tactical reloads - the top of the magazine nor the top round in the magazine have ever been very warm to the touch.
Haha nice! +10 for cowboy boots!
I should have explain my situation better. I shoot ARs long range. So ammo temp is very important to me and I monitor it very closely. Not just the top round but a few rounds benieth that one as well are all effected by heat. Its not something you can measure with your finger or simply observe by doing a tactical reload. My bad.
I'm still looking for a technical explanation of how the gases that operate the bolt heat the spent case. The carrier vents to the side. Does the hot gas heat the case as it is flying by?
I believe it does. What else is creating all that heat? 24 grains (approximately) of powder? unlikely. Hear me out. The initial blast pushes the carrier back, the left over gas then has nowhere else to go but hang out in the upper after the gas key clears the gas tube. Meanwhile the carrier is slamming back into battery with a new cartridge that just passed through all that chaos. The AR by design has a very violent action. A lot of things are happening, and a lot of heat is generated.
This is also why they get so dirty.
The scary thing is I think you believe that. Hold 24 grains of any powder in your hand and light it. No heat yet, Apply 40 000psi to any vessel and feel the walls. No heat yet. Thow the case over the flames of a fire and now we feel some heat.
https://www.youtube.com/watch?v=cxJQH-C4mWs
I will give you my opinion. The AR has a rate of fire between 600 and 800 rds per minute. If you divide that by 60 seconds(600/60) you will get a minimum of 10 rounds fired per second. This determines that it takes 1 tenth of a second to fire and close the chamber on the next round.
The trigger is pulled. The firing pin is struck. The primer ignites the powder. The powder burns inside the case and creates 50000 psi of pressure. The hot gases are pushed through the gas tube. The hot gases are routed through the gas key into the bolt chamber of the carrier. Those gases apply rearward force on the carrier. Once the carrier has moved back the bolt is unlocked. At that precise point in time the seal rings have cleared the vents and gas is vented to the side of the carrier. Half or more of the gas cleared to the right side the carrier,bolt and the remainder is pushed into the carrier cavity of the upper receiver. The carrier, bolt and pent case is moving rearward as a unit the case clears the the lugs where it is ejected. The bolt clears the round in the magazine and starts its forward path stripping the next round out of the mag and then driving the carrier forward the cam locks the bolt. .01 seconds has passed.
Gas is not hydraulic. It takes time to vent and move around to envelope the case then, unlike the powder and pressure the hot gas will take longer to heat the brass. I don't know much about physics and all with the exception of conservation of momentum and maybe coefficient of restitution but I am willing to let you educate a simple man such as myself.
I wasn't looking to make you wrong. You may even correct me on this. In the name of not spreading misinformation I think when someone sees something posted they believe is incorrect it deserves dialog so at the end of the day we are all better off and informed. After all one of the reasons we are hear is to get good information.
Drink up fellas the bar tender wants to close up and go home.
Russ left 2 hours ago. lol
Lol :D
We're just committed to making America great again, cheers
Well, as far as I can tell, the dang things are hot because they get ejected almost immediately without time to cool off in the chamber. Even a 45 acp case ejected from a 1911 pistol (which is not actuated by gas) will be hotter than anyone likes against their skin when it comes flying outta the pistol. Any heat added by hot gasses in the case of an AR is just adding a bit of insult to injury, but not enough for my lame ask to tell the difference.
Hot is hot.