If a round is fired with just a primer the force will likely push the bullet into the lands. Likely most of us have seen this and that got me thinking.

There has to be, more or less, a time difference between the ignition of the primer and the ignition of the powder, simply because the primer happens first. Some times this is apparent; hang fire. We often do a lot of reloading work assuring the 'correct' relationship of the bullet to the lands and it looks like the ignition process could be destroying that relationship and working against us! The 'problem' might be more apparent in a smaller case; the primer would create more pressure because of the smaller case volume and be more likely to move the bullet ahead of time.

For what it is worth, I load my KHornet with a slower powder and a compressed load to hopefully buffer the primer shock to the bullet.

I would appreciate your insight!

gwahir wrote on Aug 6^th, 2024 at 9:22pm:

If the rate and quality of ignition didn’t matter, changing primers would not matter.

That are many variables, so probably more than one correct answer.  Consider the extremes, cartridges loaded for a hard jam into the lands, 22 rimfire that engrave, compared to some  short bullets shot in chambers with long throats, that are briefly free floating between the case neck and lands. Similar to a 22 short fired in a 22 long chamber.

Primer pressure is not enough to expand a neck, so the bullet should be supported as it enters the bore, and enter reasonably straight. Gasses should never get around the bullet.

In the example of a short bullet or bearing surface, it’s possible for gas to beat the bullet to the bore and the turbulence make for a less than ideal entry of the bullet into the bore.

Trial and error still seems to be the best way find the best results, even after having a reamer made for a certain case bullet combination. It does seem to cut down on the time spent tho.