Does heavily compressing powder cause any harm, other than pushing the bullet back out? For example, does it change the burn rate?

quote:

Originally posted by Ackley Improved User:
Does heavily compressing powder cause any harm, other than pushing the bullet back out? For example, does it change the burn rate?

I am sure it affects burning rate. Still, there are reloading manuals that have tested and published compressed loads that considered safe... if you work the load up for your rifle.

That said, I have yet to find a compressed load that works as well as a load that leaves a little space in the shell. Most of my pet loads fill the case between the beginning and end of the shoulder. Choosing a slightly faster powder is my alternative to using compressed loads.

I have never experienced a problem with heavily compressed loads, but they can be a PITA to reload without either marring the bullet jacket, crushing the uppermost sticks of powder, or having the bullet "creep" back out. Given a suitable powder in the first place, I don't believe the burning rate is affected unless a lot of powder is damaged/broken.

The 264 and 300 Winchester rounds are two that come to mind with this problem, and when using the right bullet/powder combination, it isn't a big problem. Besides having a case full of powder, the real problem is a bullet that is "stealing" powder space. Change that, and the trouble goes away. Excluding powders such as IMR4895, I do try to find a propellant I can load at or above the 90% level.

I shoot a lot of compressed loads without problems. I have seen with IMR 7383 (a surplus powder that was only used in the old .50 caliber spotter cartridge for the 106mm recoiless rifle) that pressures and velocities climb very rapidly when the powder's compressed. Due to broken powder grains burning faster, I think.

The worst problem I've encountered is with poweder grains up in the case neck getting caught between bullet and case, crushing the case. Bad idea to fill cases up above the base of the neck, generally.

No. Compressing powder does not generally cause problems.

But be careful -- this works well only with some powders in some loads.

If you go by what you find in generally recognized loading manuals, some of them give compressed loads (i.e. greater than 100% load density) for some loads in some cartridges.