Got a "theoretical" for you "injaneers"

[ReedG]

After a few years of fooling around with 100s of reloads, I can't help but wonder if it makes any difference at all what gun powder one uses. It seems to me that the bullet is reacting to a value of pressure that is being applied to it from the gases of burning powder: let's say 50,000 lbs./in. worth. What difference does it make to the bullet what is producing the 50,000 lbs./in.? Any given powder for a certain caliber that can provide that amount of pressure should drive the bullet at the same speed to the same point of impact. Right? I mean, if you could come up with 50,000 lbs./in. from a CO2 canister, wouldn't it do the same thing?

I use my .223s as an example. It seems as I look back over my filed targets, that a given bullet (say a 52-gr. Match HPBT) shoots about the same size groups with several different powders, as long as each load is producing about the same pressure.

How crazy am I?

[propmahn]

nope wont do the same thing because it depends on how fast the powder reaches the 50,000 mark, how the pressure curve looks on the way to 50,000.  take a 357magnum load for an example;  bullseye can be loaded to reach 35,000psi but so can 2400 but the 2400 will produce a lot higher velocities.
  if i had some graphs id show you how the area under the curve is the work done on the bullet, but i dont have any.

  this should be a test and id get an A, lord knows i could use them.  after all im at purdue studying to be an engineer

[John Traveler]

ReedG,

Propmahn is right.  Propellent is not simply propellant to push the bullet out at a given pressure and velocity.

Different burning rates of different gunpowders also produce differing "ejecta mass".  Ejecta mass is the bullet, gases, and residue that is expelled when a gun is fired.  All of these things directly affect projectile acceleration, muzzle velocity, gun recoil moments, amount of recoil, barrel vibration, etc, etc.  The physics and dynamics of firing a gun with a given ammunition to a given velocity are very complicated.  

To the hobbyist/shooter/reloader, experimenting with combinations of bullets, powder, primers is still the most productive (and fun!) way to make an accurate shooting rifle/ammo combination. :shock:

[Reloader]

Good gosh!! Don't ever get the rumour going that reloaders can get by with less stuff.  My wife's been trying to press this point home for way too long. :lol:

[Flint]

Burning rate is a perticulaly important factor in semi-auto gas operated rifles.  The size and location of the gas port and piston are critical, and this was a factor in redesigning the M-16 in the early years when the govt bought ammo from Winchester to feed in a rifle designed for Remington ammunition.  The bolt velocity went up, the reciol buffer failed, the full-auto rate was too high and failures occured.

[Jose Grande]

I remember years ago folks saying Bullseye wouldn't blow up a rifle for some reason or other. The NRA finally tried it & the explosion blew the reciever all to pieces.
The point is : use two or more manuels & never wander off on your own in the world of reloading. A bolt coming backwards through your eye could be hazderdous to your health. IMHO

[John Y Cannuck]

Has anyone mentioned accuracy yet? Burn rate affects barrel harmonics, bullet upset, and a bunch of other stuff, that can shrink or expand your groups.