I was talking with my Nevada gunsmith who's smithing my .30 Carbine Blackhawk.
Yes, let him smith if he provides the services you want. Remember this; just because he's a gunsmith, even a good one, does not know he knows much about interior ballistics. Some do, some don't. Let's not start campfire stories...
Gunsmith says,
jski said:
Without the ability to roll crimp these cartridges, because they're headspaced on the case mouth, you're really not getting all you can from these cartridges. Simply put, the harder it is for a bullet to escape the case, the more tightly held the bullet is, the more completely the powder will burn in the chamber and barrel. And the higher the pressure level will get.
This is ALMOST correct. With the bullet slightly retarded from leaving the case, burn will be more complete and uniform. Crimp, or 'more' crimp is one method. So is loading (usually a rifle) bullet into the leade. So is sizing the neck down smaller to create a tight 'grip' on the bullet. So will some form of sealant. (I recommend against Super Glue.)
jski said:
Now here's the interesting point: he stated that best way to compensate for this is to load heavier bullets. Sound reasonable?
Not really.
Yes, a heavier bullet will retard bullet movement and cause a more uniform and complete burn. However, with the same powder charge, the heavier bullet will not be launched as fast (muzzle velocity). Not to mention the powder charge may be an overload with the heavier bullet. The 'standard' weight .30 Carbine bullet is 110 grains. The next heavier bullet weight (quick look) is 125 grains. But it may be too long to load without the tip of the bullet protruding out the face of the cylinder. (Maybe it will fit, but I'd bet 180 grain bullets or so won't; there's a limit.) Obviously not a solution. One could load the heavier bullet deeper into the case, but this means reducing the 'chamber' area, requiring a lesser powder charge.
Face it; the cartridge has limits - as do all - and one is limited by the mechanics of the instrument, the physics of the cartridge firing and so on. Not to mention a Blackhawk barrel is shorter than an M1 Carbine barrel.
Don't worry about "...not getting all you can...", you probably are. Wear earmuffs (those suckers are LOUD) and enjoy.
I forgot to mention something you said. About a bullet doing 1200 fps leaving the barrel in (so much time)... The bullet is stationary at the chamber end and moving 1200 fps exiting the muzzle. So the average velocity of the bullet - and transit time is based on 'average time' - is 600 fps. But all the powder in any firearm is consumed within the first few inches of barrel travel.
Yes, some powder isn't burnt. However, it wouldn't be burnt if one had a six foot barrel. And the muzzle flash is NOT unburnt powder.