The effect of space in the case?

[roscoe]

I was tinkering around with a mild 30-30 load (700x and 110-grain jacketed slugs) and realized I had made them all a bit short. The manual says 2.55", but these were 2.5". That 20th of an inch isn't very much, so I didn't worry about it.

But it got me thinking - would seating them lower or higher have any real effect on the velocity? Either way, there is still plenty of room, so the powder wouldn't be compressed, but it made me wonder if having extra room in any way dissipates the shockwave.

 

[sequins]

Yes, seating a bullet with a shorter cartridge overall length will generate more pressure. Sometimes MUCH more pressure.

 

[Project355]

The effect relative to case size should be considered. Seating your .30-30 about .050 inches deeper on a case that amount of volume is much different than seating, for example, a 9mm P .050 deeper. You're just eating up what little volume the case has by doing so.

 

[Walkalong]

In that application it's doubtful it will be an issue, but yes, seating depth matters when it come to pressures. In 9MM .020 could be bad.

 

[fxvr5]

With rifle cartridges (which have a lot more space than pistol cartridges), seating the bullet deeper can result in less pressure and less velocity. This works up to a point, then the pressure will start to increase as the bullet is seated deeper.

https://www.hornady.com/team-hornady/ballistic-calculators/ballistic-resources/internal-ballistics

Pistol rounds have less space to work with, and pressure almost always goes up as the bullet is seated deeper.

 

[film495]

if you're not shorter than the minimum OAL, can't see why it would be an issue. 30-30 headspaces on the rim, and the OAL is bullet specific - a flat or rounded bullet, will change the seating and grip in the case - I'd look up the OAL specs for the bullet by the manufacturer of the bullet and go from there.

If you are near a max load, and shorter than the listed OAL, playing with fire you are.