bullet seatting depth??

G

gundogblue

Guest
I've read that the closer a bullet is to the lands, the better the acurecy will be, if this is true, what is the best way to determine the best OAL of the cartridge for my rifles? Right now I adhere strickly to the OAL of a particular cartridge as stated in my Lyman manual.
Thanks,
gdb :confused:
 
Two tools can be purchased that will be useful -- this presumes you already have a vernier caliper.

You need an OAL (overall length) guage, and a bullet comparator.

These are for sale in most reloading shops or national catalogs. The OAL guage costs about $26, as my memory serves me.

One comment I did not see made in the posts thus far-- it can be dangerous to jam a bullet into the lands if you do not reduce powder charge. It can kite up the pressures.
 
Like most things in life

needing to have a bullet touching the lands isn't always the place where accuracy lives. Some barrels shoot best when the bullet is "Jumped" or there is a gap between the bullet and lands and sometimes quite a big gap. With regard to Factory rifles that have long throat areas, jumping may be the best solution.

From my point of view, you need only a caliper and some sort of comparitor to find the lands. Assuming you won't bump your case shoulders back too far you can find the exact proper OAL by loading a bullet into a dummy round long and closing the bolt. With light neck tension you won't be pushing the bullet into the lands more than .005 plus or minus. To find where the bullet just kisses the lands push the bullet into the case at .002 each time until there is just a faint hint of the lands. ( Polish the bullet with .0000 steel wool each time you cycle the bolt )

You will need to check each lot of bullets you use to be sure they touch in the same place as the lot you are currently using.

One of the pals who travels with me to shoots finds good results with his tight chambered Brnchrest Rifle at .009 off the lands so using this as an example breaks the myth about needing to touch the lands. Others I have heard of also jump a bit with good results. Good Luck. Pete
 
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I was told by a gunsmith that if the leade angle is shallow as is typical on match barrels that the bullet should be as close to the rifling as possible from jammed to 5 thou or so off. If the leade angle is steeper, as in many factory barrels that the bullets usually like to be jumped. I've got a CZ .222 that does NOT like bullets up close to the rifling, and it's got a steep lead angle, so.... On the custom barrels I've got the bullets generally like to be as close as they can get.
 
I use the stony point COAL guage, and it works really well for me. It look like this http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=12634&title=OVERALL+LENGTH+GAUGE They also sell a tool that clamps to your caliper to determine the OAL based on the ogive, giving you a much more accurate reading.

The reason I like this one is that I load for more than one caliber. Instead of buying a seperate dial guage for each caliber, with this one you can simply buy a modified case for each caliber, and only have to buy the tool once. Works great, and makes developing COAL a snap.

My forever humble .02
 
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