Newbie questions about cartridge lengths

[.Ben]

ok so i wanna kno if i have a grasp on this....smaller cartridge capacity with more poweder means higher presures right? so if i seat bullets to a leser depth with the same given load it should lower the presure?

and bullets should be seated as long as possible while still being able to workin the the magazine/chamber?

 

[cosmic]

Seating too deep or too shallow will cause pressure increases. Too deep for the reasons you state, although there is quite a bit of latitude here. As the bullets are seated closer to the rifling, the bullet doesnt get a chance to get a "run" at the rifling, also causing a pressure increase.
Unfortunately, many internet pundits say you should be a few thou, or even kissing the lands, for best accuracy. While this may be true for benchrest shooting, I dont advocate this for recreational shooters and hunters.
For the average hunting rifle, the benefits of this practice vis accuracy are marginal. Couple this with the problems that may ensue:
- inability to hold the small clearance from round to round, due to variations in die performance, and bullet shape. (deformed soft point tips, variations in ogive profile from box to box of bullets from the same manufacturer.)
- inability to use the ammo in another rifle. (Doesnt sound like an issue, but will you remember that those reloads you made 5 years ago were specific to a given rifle.)
- unreliability in the field - stuck bullets, etc.

I have several rifles of the same calibre. I dont want to work up dedicated loads to each rifle, with specific OAL's. So, I find the one with the tightest rifling, and put 30 thou clearance on the OAL. I keep detailed records of my efforts.
I now have universal ammo that can be used in any of my rifles. Its "tighter" than factory ammo, as I can usually see the cannelures c/w at least 1/16 in clearance. And I can get cloverleaf groups with me and the rifle doing our fair share.
Suggest you focus on being able to optimize loads vis bullet weight, powder, and charge. Also, the bedding of your rifle. Dont get hung up on this OAL with minimum clearance stuff.

 

[H4831]

Ammo to be used for hunting has to be able to work through the magazine. This is the critical factor regarding seating the bullet. I seat them by checking if they will cycle through the magazine, then the finished product will be very close to factory ammo.
In building up loads I have taken my loading outfit to the range, to load and shoot. I have loaded far out, to where, with my 30-06 Husqvarna, with CRF feed, I have to take the bolt out then fit the cartridge in the extractor, and bush the bolt back in to feed the round. I can detect no difference in pressure, in whether the bullet is tight against the lands, or has the normal amount of clearance. With 4350 powder I go grain at a time higher until there is a definite show of excess pressure, then I back off, probably two grains, and there is my load.
As stated, this excess pressure occurrs at the same powder charge, whether the bullets are seated with clearance to work through the magazine, or whether the bullets are tight against the lands.