Thread: Show me your lightweight rifle

Definitely don't want to derail this thread either, but it is useful to add that I've read a lot about this and there's some useful things to know about powder deflagration. First, all of the powder THAT IS GOING TO BE BURNT is consumed in the first few inches of the barrel regardless of burn rate. What the barrel does is contain the expanding gases to push the projectile out of the bore - longer barrel equals longer push. One of the criticisms of Quickload (and GRT) is that the percentage of powder burnt indicator implies that this is a variable where the aim should be to achieve close to full burn. This isn't something the end user can control at all. There will always be some unburnt kernels blasted out of the end of the barrel as part of the ejecta.

That leads nicely to the next point - muzzle flash etc is not powder burning outside of the muzzle. It is high pressure and high velocity gas igniting on contact with the oxygen in the atmosphere outside the the bore. What you definitely do get with a relative slower burn rate compared to a faster one is higher muzzle pressure (because of that bigger push) - all other things being equal. This can be either a useful thing (higher muzzle velocity, higher port pressure to operate semi or full auto firearms) or a bloody nuisance (more 'wear' per shot in a suppressor, bigger boom without).

This 'common sense' misunderstanding of internal ballistics (that shorter barrels needs faster powder) needs to be challenged as it could lead the unwary handloader into very dangerous territory. Always consult the handloading manuals. The optimal range of powders for use in a given situation is determined by case capacity relative to the bore size, and further moderated by projectile weight and composition.

If anyone wants to know more about any of this, the Hornady podcasts that focus on the scientific aspects of shooting are really good I think. The ones that focus on maths and statistical validity are the most useful, but that's definitely a subject for it's own thread!!!