What is a good starting point for seating depth.


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Comrade Mike
April 23, 2013, 10:45 PM
I've read a lot about a method to determine the length of your throat by seating a bullet long and then closing the bolt to push the bullet deeper into the case thus providing you the length of your throat.

I have yet to try this as I'm away from my reloading bench at college and the only rifles I've loaded for thus far have had; an absurdly long throat (swedish mauser) and a semi automatic (AR15). I followed Swede M96 expert's advice on the mauser and the manuals on the AR.

So my question is, once you've determined the distance to the lands, whats a good starting point as far as load developing goes. I've heard anywhere from .02 off the lands to .05 off the lands. Any advice on a good starting point before I try playing with seating depth?

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Fire_Moose
April 23, 2013, 11:03 PM
I've always heard .015" from the lands.

Sent from my CZ85 Combat

flipajig
April 23, 2013, 11:59 PM
I've loaded several rifle calibers with my bolt and single shot guns I start 0.10 off the lands. Remember start low and work up you can get into pressure problems if you don't
Flip

Comrade Mike
April 24, 2013, 12:07 AM
I always do a ladder test, i think Ill give .02 a go.

Canuck-IL
April 24, 2013, 01:07 AM
It depends significantly on the bullet ... Hornady AMax are not particularly jump sensitive. Berger VLDs are incredibly fussy.

Conventionally, if you can reach that far and still keep the bullet in the neck, you'd start at around .01

/Bryan

James2
April 24, 2013, 01:28 AM
"What is a good starting point for seating depth?"

Hmmm, for starters, I suggest the OAL given in the manual where you got your load.

If you go to fooling around trying to seat it so many thou from the lands, that is fine too, however, remember it needs to fit in the magazine and load from the magazine and chamber freely. Sometimes you can't have all these things.

You will never know what is best for that particular rifle and bullet combo until you try some different things and see how they group. Wish there was a better answer, but its pretty much try it and see. It is time consuming because you need to work up some loads in batches of 4 or 5, whatever you decide to use for a group number, then go shoot and see how they perform, then try some more. Keep records.

It is well known that changing the seating depth can change the group. It may be worth your time and effort. Depends on what your goals are. If you are wanting something accurate enough to hit a deer at 100 yards, likely your first try will do.
If you are wanting to shoot prairie dogs at 200-300 yards perhaps not. And if you are after a group you can cover with a dime at 100 yards, you will need to work at it.

Whatever the case....... ENJOY!

Canuck-IL
April 24, 2013, 01:51 AM
... remember it needs to fit in the magazine and load from the magazine and chamber freely
Really only the 3rd point ... a lot of mid and long range is shot by single loading - even 200 yard HP offhand.

/B

gamestalker
April 24, 2013, 03:19 AM
What I've been doing, is I seat a bullet long and then I hand chamber it so I can feel the bullet begin to stick in the lands. I continue seating deeper until I can hand chamber the round with lots of pressure, and the cartridge will drop out of the chamber when I tap on the barrel with my hand. I am now at zero for all practical purposes. I then continue seating deeper in .010" increments, and shooting 4 or 5, 5 shot groups at each increment.

The nice thing about starting at the lands for me is, I can use the powder charge I worked up to at all other OAL's. It saves me powder and bullets in the work up process, because I don't have do much powder adjusting until I'm finished with the OAL, and then it's usually very close to target anyway, because I worked up to the max safe pressure while at the lands.

There is really very little to be gained by working in increments of less than .010" Most bullets will have as much as .010"olgive inconsistencies anyway. I would think .010" would be a reasonable increment to work with with most bullets.

Don't bother trying to get up close to the lands on an auto loading rifle. Regarding OAL, magazine fit, and reliable cycling take priority with those type of actions.

GS

BillB204
April 29, 2013, 08:12 AM
First, throw the book OAL out the window. It may be good for measuring appropriate mag length for auto loaders, but it's worthless for maximizing group size. Remember, the olgive for virtually every bullet weight, type and manufacturer is going to be slightly different. That difference is going to mean a different seating depth to lands for each bullet type and manufacturer. And a difference of just .02 in seating depth could mean a difference of .5 moa. So you have to measure each bullet type to get an accurate "to lands" measurement.

Second, measuring by inserting the bullet into the case mouth and closing the bolt will not give you an accurate or consistent "on lands" measurement. Unless the neck is loose enough to allow the bullet to move into the case with zero resistance, the bullet will be seated into rather than on the lands by some amount. And if you keep the neck loose enough for the bullet to move freely, the bullet will move when you pull the bolt back. That being the case, the best way to measure each bullet type is to use a bullet depth measurement gauge like the Hornady OAL case gauge (http://www.midwayusa.com/product/570611/hornady-lock-n-load-overall-length-gage-bolt-action).

Now to answer your question. Optimal seating depth is going to be different for every caliber, every rifle and every bullet type. Sometimes the best depth is on the lands. Sometimes the best is slightly (.10) into the lands (Bergers). In my experience, most of the time the best is between .010 to .030 off the lands. When looking for the best seating depth, I load and test initially with 3 group tests (to save components) at .010 intervals. I narrow it down then confirm with 5 group tests.

FWIW, neck tension, case prep, primers, powder and powder amount will also have to be optimized for the best possible groups. And if you're shooting 300+ yards, you have to load to minimize deviations in velocity (SD). In my experience, a looser neck tension and seating at about .020 off lands generally gives me the best groups and the best SD. GOOD LUCK!

243winxb
April 29, 2013, 09:14 AM
Seat bullet base @ neck/shoulder junction for factory chambers. Then try different powder burn rate suited to the cartridge. This does not always work because of the need to fit a magazine or leade. http://img.photobucket.com/albums/v663/bwestfall/RELOADING/3D-308-doughnut2.jpg

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