Bullet seating depth pressure question

[buckman]

Does seating depth change chamber pressure? If yes in which way will pressure be reduced or increased.

[elkhunter11]

The jump to the lands can effect chamber pressure, but is isn't as simple as some people think it is. In most cases increasing the COL causes decreased pressure, until the bullet is seated close to the lands. Then the pressure increases, because the bullet has less momentum when it strikes the lands, and the force required for the lands to engrave the bullet increases.

[omega50]

Speaking from having older rifles with advanced throat erosion I often had to exceed max OAL to get anywhere close to the lands. Not a huge issue until I tried to use some of my handloads in a buddies rifle and could not close the bolt.
Aha moment and I retired the rifles and pulled all the bullets from those loads. Feel lucky that the bolt wouldn't close as the pressures likely would have been nasty

[obsessed1]

Simple answer is this.
As the bullet is seated deeper into the case the internal volume is decreased causing higher pressure
On the flip side pressure can increase as you get your overall length closer to the lead/throat rifling.
So simple answer is yes lol

[dth_]

On top of what others have said, its also worth noting that the pressure increase seen due to seating into the lands often comes on pretty abruptly. Its a good idea to get an OAL gauge and headspace comparator so you know the CBTO length you need to touch your lands and increment seating depth slowly up to that number.

[catnthehat]

The above answers are all pretty much correct and the newer hand loaders must also realize also that a length and load for a particular cartridge is what it is for that particular cartridge , and that they may not transfer to another rifle with the same chambering.
Of the four .308 rifles I have in my vault ( three match rifles and one hunting rig), none of them will interchange ammunition even with lighter loads , and two have very long throats.

Pressure is a strange thing and it can be very misleading .
If we start getting extractor marks , stiff bolt lift etc, you have already gone last the safe pressure for your rifle even if the book says we are only in the mud range for that cartridge!
Same thing goes for accuracy, a rifke's best combination for accuracy may not be anywhere near what the books say for OAL, and we must learn to accept that !
Cat

[1100winger]

Of several 6.5 swedes none react the same although some can be deemed safe to interchange but it affects accuracy a lot. I emailed Swift some time ago re a loading question and extrapolation of data - one of their engineers phoned me and we had a long discussion re powder choices, fullness of brass, cartridge length, and distance to lands. It was quite enlightening. At the end of the day, each rifle is unique, must be considered and respected as such.

[birdseye]

Also remember to visually and touch the neck in the brass after bullet seating,if the sizer dies is not set properly it can crush or bend the neck significantly or minimally.... good luck stay safe