Effect of friction of boolet passage on barrel heating

[wmitty]

Is the heat generated by projectile friction a very minor factor in relation to total heat generated in the firing of a cartridge in a rifle?

[rockshooter]

Dunno for sure but I think so- evidence would be the hot .308 case down the back of my neck.
Loren

[wmitty]

rockshooter

Been there, too. I was wondering if someone had fired the same powder charge behind boolits and then jacketed slugs to see if barrel heating was the same or similar.

[runfiverun]

boolits have lower friction than bullets.

[44man]

It will be minimal, too short of time for one thing. Powder burning exceeds the melting point of steel and is what washes out the throats if the steel can't absorb the heat fast enough. Yet it will not melt a boolit or burn filler because they are gone too fast. A bullet will be hot if picked up fast but will not burn you. I think the brass is hotter then a bullet.

[Larry Gibson]

Is the heat generated by projectile friction a very minor factor in relation to total heat generated in the firing of a cartridge in a rifle?

Yes. As mentioned the heat generated by even jacketed bullets is minuscule compared to the heat generated from the powder burn. Also as mentioned cast bullets of lead alloys generated much less friction. I'm sure there are engineers here who can calculate the potential heat generated from both.

Larry Gibson

[prs]

Now, this is an apples to pears comparison; but my experience with 45 Colt black powder cartridge in the Marlin 1894 Limited begs to consider friction derived heat. Using the same black powder lube, same full powder charge of same powder, only difference being the boolit used: Lee 452-255-RF fired at reps common in cowboy type shoots for 50 rounds, barrel so hot one can NOT hold the barrel with bare skin without burns. Same set-up, only using the PRS454-250-RF boolit, barrel is "hot" but can easily be grasped and held without burns. The black powder specific boolit holds a tremendous reservoir of lube and such might modify the combustion temps like high octane fuel, but I doubt it. I believe it is the friction reduction. Then again, "smokesless" propellant does not so foul the barrel to where friction may be a real factor; but in BP it is likely that friction is a considerable heat contributor. Similar result comparing shotshell loads in 2 3/4 dram 16ga with black powder rounds with and without lube wads. Lube wad rounds leave the barrels way less hot than those with dry wadding.
prs

[felix]

Jim, the projectiles are too hot to hold as well. I caught one in mid-air and had to drop it just as fast as it was caught. A 220 Craig nickel-chrome projectile, shot at about 1800 or so, hit a log or something buried behind the beer can target at about 50-60 yards. I was standing about 35 degrees away from trajectory, and about 35 yards back towards the shooter (my wife). Full 308W case using 5010 in a model 99. Circa 1962, Columbia MO construction site. Absolutely zero damage to the projectile. Still have it somewhere around here. ... felix

[375RUGER]

I'd ask the guys in the airgun forum how hot their barrels get.

[44man]

I'd ask the guys in the airgun forum how hot their barrels get.
I was thinking of that myself. Shoot each boolit from an air gun and a powder gun at the same speeds, catch and measure boolit temps. Compressed air release is still hot but not like powder.
Notice a rifle gets hot first at the chamber end and it moves out.
Then a bullet will get hot out in the air as it compresses it. A bullet will generate a lot of heat when it hits something and converts energy to heat.
Friction also means wear so if there was that much our barrels would not last long.

[wmitty]

So the heat generated by friction within the barrel is negligible compared to the heat from deflagration of the powder charge. If water or a water/alcohol mix were injected into the chamber/throat very soon after pressure dropped to ambient, could any benefit be realized as far as throat wear?

[btroj]

Not really. The throat gets eaten up by the heat generated by the powder burning right behind the bullet. Think about it, that heat only last a few milliseconds. Figure that if a target rifle lasts 2000 rounds on a barrel the throat only took that heat for a few seconds before burning out. Kinda odd to think of that way, isn't it?

The throats on stainless and chrome/moly barrels wear differently. Chrome/moly actually will often last longer but it tends to get a rougher wear pattern in the throat with time, stainless tends to get a smoother wear pattern which is easier on passing bullets. In general that is why most target rifles use a stainless barrel.

[44man]

Talking on a PM made me remember air release is cold, I was thinking of initial compression in a spring gun before the pellet leaves but the air might cool the barrel fast so it might get us nowhere.
We know some powders make a gun a lot hotter then others, like Lil'Gun so that might be why a bullet can get hotter.
Then bullet construction might also be a big factor as Felix pointed out.
I am still inclined to lean towards powder doing the deed.

[fourarmed]

I just did a quick calculation. If it takes 50 lb. to push a 180 grain boolit through a 24" barrel, that is 100 ft.lb. of energy, which is about 32 calories. The specific heat of lead is .031cal/(g K) and 180 grains is about 12 grams. That much energy would raise the temperature of that much lead by 86 degrees Celsius. That would put it at about the temperature of boiling water. Since it happens so fast, the temperature change is mostly at the surface of the bullet when it leaves the barrel, and so it cools rapidly from the air. Boolits don't get that hot when slugging a barrel because it happens very slowly, and the heat is shared with the barrel steel, which is much more massive.

[BAGTIC]

Compressed air cools as it expands so it adds no heat to the barrel. Now if the expanding cool air hits an obstruction after exiting the barrel it will be compressed again and a thermograph will show it being hottest at the point of initial impact with the temperature once again lessening as it spreads outward.

[Bret4207]

Now, this is an apples to pears comparison; but my experience with 45 Colt black powder cartridge in the Marlin 1894 Limited begs to consider friction derived heat. Using the same black powder lube, same full powder charge of same powder, only difference being the boolit used: Lee 452-255-RF fired at reps common in cowboy type shoots for 50 rounds, barrel so hot one can NOT hold the barrel with bare skin without burns. Same set-up, only using the PRS454-250-RF boolit, barrel is "hot" but can easily be grasped and held without burns. The black powder specific boolit holds a tremendous reservoir of lube and such might modify the combustion temps like high octane fuel, but I doubt it. I believe it is the friction reduction. Then again, "smokesless" propellant does not so foul the barrel to where friction may be a real factor; but in BP it is likely that friction is a considerable heat contributor. Similar result comparing shotshell loads in 2 3/4 dram 16ga with black powder rounds with and without lube wads. Lube wad rounds leave the barrels way less hot than those with dry wadding.
prs

2 different boolits give you 2 different pressures/burn rates. I would lean towards the difference in heat coming from the burn, not the boolit.

[243winxb]

I have read that the peak temperature is around 5,000°F from the powder burn, in a high powered rifle with J bullets. But as said, the peak is so short that it takes many rounds to produce fire/heat cracking in the throat.