Seating Depth Question

[dungheap]

If one is going to experiment with seating depths, should he/she start deep and move out, or start at "into the lands" or thereabouts and then gradually seat deeper?

My practice has usually been just short of the lands or as long as practical, and leave it that way.

Chances are there's no hard consensus, but I'm curious as to what others have been doing, and why.

[Pahoghunter]

Some time ago I developed method for working up loads. Part of the method is the seating depth. I start with my first load touching the lands. Then five more loads each .005 further off the lands generally you will hit a "sweet spot" from which to work. Hope this helps.

[wally bennett]

Originally Posted by Pahoghunter

Some time ago I developed method for working up loads. Part of the method is the seating depth. I start with my first load touching the lands. Then five more loads each .005 further off the lands generally you will hit a "sweet spot" from which to work. Hope this helps.

Thats how i do it i read somewhere that touching the lands gives the highest pressure so moveing it away bit at a time puts you into a safe zone in theory anyway
Wally

[brians356]

Originally Posted by wally bennett

Thats how i do it i read somewhere that touching the lands gives the highest pressure so moveing it away bit at a time puts you into a safe zone in theory anyway

If the bullet is truly "jammed" hard into the lands, not "just touching", that's true. But as you seat deeper into the neck, you are also decreasing net case capacity, which will normally increase pressure (and velocity) accordingly, for a constant powder charge. So "jammed" is kind of a special case, which is why I start with some bullet jump (usually 0.020" from "jammed") and try jumps both sides of that in 0.003" increments to find a sweet spot. As it happens, I almost never finish up with a load seated into the lands now.

Here's the approach I am using now, and I really like it:

http://forum.accurateshooter.com/ind...opic=3814361.0

[montdoug]

Originally Posted by Pahoghunter

Some time ago I developed method for working up loads. Part of the method is the seating depth. I start with my first load touching the lands. Then five more loads each .005 further off the lands generally you will hit a "sweet spot" from which to work. Hope this helps.

I do it quite similar but a bit different.
I find that just touching point and then back off a couple thou. I then find the powder charge that shoots best there at which time I start backing off .005 a whack and load 5 of each to test in case I yank one. I use to load 3 but I always worried that pilot error might work me past a real dandy load. I usually only back out on varmint loads to .020. Once I find the depth it likes and more importantly the bullet it likes, I go back and finalize the rifles charge preference.
I use to start with the bullet into the lands until I pulled a few to many bullets out of the cases leaving an action full of powder. Sometimes a guy looses the shot he chambered a round for and wants to take it out of the chamber unfired. A lotta pros working up accuracy loads seated squarely into the lands but most definitely some cons as well IMO.
That's been my approach for a long time.
Hunting loads I start 5 thou off and work back from there.

[hd833]

I seat a bullet into a resized empty case. I then paint the tip of the bullet with black magic marker. Yes magic marker. close the bolt and keep reseating the bullet till I see no more rifling marks on the tip. Each time repainting the tip of the bullet. I guess the correct term is the ogive of the bullet. Simple but efficient. Never had a problem yet. And if I'm uncertain I'll reseat another .004-.005" deeper.

[Big Al]

Originally Posted by hd833

I seat a bullet into a resized empty case. I then paint the tip of the bullet with black magic marker. Yes magic marker. close the bolt and keep reseating the bullet till I see no more rifling marks on the tip. Each time repainting the tip of the bullet. I guess the correct term is the ogive of the bullet. Simple but efficient. Never had a problem yet. And if I'm uncertain I'll reseat another .004-.005" deeper.

I use this method and think it is the most accurate way of determining base to ogive dimension. Remember to use a fire formed case with not quite full neck tension and also to use the same bullet head each time when measuring. If the bullet head gets messy its easy to remove the marker film and start again with some alcohol.

[wally bennett]

Once i had a good round i would measure C O A L then make up my other rounds to that C O A L .
MISTAKE !!!! I was getting marks on my heads and heads left in the rifling even though i was supposed to be 0,005" out of the ogive.
ON checking the length they where all 1.805" (17A/H IN PACNOR BARREL) but some had touched the rifling and others not so i checked my 200 box of 20gr V/Max and found a variation of 0.011" in the heads that seemed to be the plastic nose variation.
I now use my press and fit a set round in it and furn down the die till it touches the round very lightly with the round in the up position lock off the ring and load from there.
Never had a load of propelent in my action since.!
Wally

[Big Al]

Never measure COAL as a means of tuning seating depth as the length of a bullet head can vary far too much as mentioned, Ive seen them vary by as much as 0.025".

Always use a comparator and measure cartridge base to ogive CBTO, this means the measurement is accurate in terms of where the ogive is in relation to the lands. Also remember that this CBTO measurement only applies to that type of bullet, if you change bullet head you have to start all over again as shapes of ogive differ and the hole in the comparator isn't an accurate indication of bore size.

[brians356]

Originally Posted by Big Al

Always use a comparator and measure cartridge base to ogive CBTO ...

Very well said. Did you pick that up in the Toon Army?