.223 vs barrel length

Quote:

It doesn't make any difference when the powder is "burned out", as the gas pressure will still push the bullet.

Whether burned out at 12 inches or 15 inches, 26 grains of powder makes ~26 grains of gas, and that gas takes up the same amount of space, no matter what.

The speed of the powder might make small differences in pressure, but not enough to stop the acceleration down the barrel.


Obviously the pressure will push the bullet out of the barrel. If the powder is burnt the pressure has peaked so when does the velocity peak? We do know that once it leaves the barrel velocity starts dropping off. We can assume that at some point velocity starts dropping off in the barrel. Ideally it would be at the same time the bullet leaves the barrel. I would not want the velocity peaked with 4" of barrel left.
 
On 5-3-08 I was cronographing some loads for my 26" Rem.The load was 28.5 gr H335, Win small rifle primers, Lapua once fired brass and Hornady 40 gr v max bullet. Bullet was seated .010 off the rifling. Rifle shot a 15 shot group into .445" with an average velocity of 3846 fps. SD was 9.9
This is over 200 fps faster than any loading manual I could find. I did notice that most of the manuals used rifles or barrels in the 22"-24" range. I was thinking at the time that the longer barrel was accounting for the big difference in velocities and I sure as hell wouldn't cut a couple of inches and expect higher velocities. Frank
 
40+ years ago when I first started studying, not loading, reloading & all that emcompasses it, I remember a lesson about case capacity, caliber, bullet weight & barrel LENGTH determining what burning rate of powder to use. IE. 'when the useful burning rate of powder is used up in the particular barrel used.
SamSpade & I remember these lessons & I've yet to see any proof to dispute this theory.
Chronographs may testify to this. Maybe I need to be enlightened.
Please do.
 
The bullet rquires a certain force to be moved down the barrel, we'll say 200 lbs as a guess. Divide that by square inches of Bore, in the case of .224" that is .0394 in^2. from there you have the PSI needed to accelerate the bullet. My guess figures to 5076 PSI. If the pressure is below that, the bullet will decelerate even with positive pressure behind it. So whenever the pressure hits exactly that as the bullet is headed down the barrel, that is where it is at its peak velocity. As all handloaders know, that point will vary greatly depending on powder, load, bullet and even bore and chamber consistancies. Realistically though, i'm willing to bet that no bottleneck cartridge ever slows down in a barrel of comercial length. I've heard tell that a 22lr reaches peak around 14 inches or less from approx 4 grains of powder and a 22 mag is around 18 inches from approx 7-8 grains powder. By even the most conservative calculations to account for differences in the above stated factors, that would put a 223 peak out to about 4 feet or more.

FWIW: I would expect pistol cartridges to get possibly get there in rifle length barrels since they are similar to the rimfires in capacity/bore relationship

This is just some science for you to chew on for awhile

Cheers,
 
That is very interesting. It has some logic to it but for the differance in burning rates, from slow to fast, in that if the charges were the same weight?
What I'm referring to is if I were to start to work up a load for a certain gun I would start by caliber, case capacity, bullet weight & barrel length as a guide. Now all I do is look for a load from a manual for a proven load. The 'figgerin' part is no more.
I still believe in my original comment about this because of the logic of powders with differant burn rates.
 
Here is an experience that I had. When developing a load for a 6mm with a barrel length of 25.5" I started with IMR4350. I could get the velocity up to about 3450 fps but couldn't get it much over that no matter how much I increased the charge. Switched to IMR4320 (a faster burn) I could get the velocity a little over 3600. My theory is the slower powder never got fully burnt in the barrel? More evidence to that theory is that the 4350 load had a lot more muzzle flash. This may not happen with different calibers or case capacities but it did in this instance.
 
Another huge factor is hunting with a shorter vs longer barrel. A 20" barrel while handy is probably doing hearing damage at every shot. Hearing damage is accumulative. The 24" barrels seem to get the concussion away from your head also.

Good luck!
 

Any high power rifle with any length of barrel will cause hearing damage if you shoot without hearing protection. Please don’t do that or you’ll be like me saying, “HUH” every time someone says something.
 
Amen, NE223, Amen. We should all use electronic ear muffs when we hunt. My ears ring all the time. No doubt that I will be stone deaf when I'm 80.
 
It doesn't matter what "speed" powder you are using, fast or slow. It will all be burnt up in the barrel. A rifle barrel is more than long enough to burn all the powder. That is why the pressure curve starts downward while the bullet is still in the barrel. All the powder is burned up and the expansion of the resulting gases pushing the bullet down the bore expands the available volume and the pressure goes down. Do you want to know when the powder is burned up? Look at the peak of the pressure curve. It usually appears in the first couple of inches. There is no unburnt powder left after that.

Bullets will fly faster from a longer barrel because the expanding gases have longer to work on the bullet. There is a theoretical maximum length, but it is not 24" or 26" so don't worry. Barrel length should be the longest you can get and still be as handy as you want it to be. For a strictly p-dog rifle, 24 or 26 is probably not too long. For a coyote rifle, I would limit it to 20" max because you have to carry it and shoot it at wierd angles so it has to be handier than a 24 or 26.

Some barrels are just "fast". I have a .300 WM that shoots everything faster than it "should" so I watch the powder and keep velocity in the range of max from the manuals. There is no free lunch. Higher velocity means higher pressure. You may have two identical guns and one shoots the same load 100 fps faster than the other. The faster one is experiencing higher pressure. No way around it.

Fast Ed
 
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