OAL versus max pressure

[Zey]

Ok so max pressures. Does it increase if the bullet is on the lands, or in the lands?

My theory inside the computer on my shoulders is that 'on the lands' would slightly increase pressure as the bullet cant move until slightly more pressure is built up. 'In the lands', lets say, 20 thou for example, would be slightly higher still. If the bullet approached the lands with momentum, it would encounter the rifling with a little kinetic energy, thus helping it along. Plus, the chamber volume is larger and ever expanding if the bullet is already moving before contacting the lands.

My question comes from my friend has a compressed load and wants to seat the bullet 0-2 thou from the lands but he's afraid because it's already pretty decently high pressure as it is.

Quite possible I could be over thinking this aswell...

 

[david doyle]

he's afraid because it's already pretty decently high pressure as it is.

nuf said right there.

 

[kombayotch]

After measuring this many times with my Pressure Trace system, the conclusion I have come to is: sometimes. On some loads the pressure has increased drastically when moving the bullet into the lands, on others, I has had almost no effect. It tends to have a greater effect with faster burning powders than with slower ones. Which makes sense... but, there is no golden rule.

With any type of change (especially one this drastic), you definitely want to back off and work back up again.