How do you measure bullet seating depth?

BTRACK · 04-23-2003, 12:03 AM

How do you measure bullet seating depth so that you achive the closest tollerance relative to getting the bullet enguaged with the lands and groves? Is this just a minimum depth seating achived by closing the bolt on an underseated bullet... then just double checking to see if the cartridge will fit and feed in and from the magazine or is their a tool you use to measure the depth?

It may not matter now but I want to experiment with this eventually.

Thanks in advance - BTRACK (||)

LARRY338 · 04-23-2003, 05:34 AM

It will matter you will find out. This one thing might make more difference than any other single thing you can do. Seating depth and cartridge concentricity. Take a fired case and run it into your sizer die just about 1/16" so that much of the neck is sized. Then seat a the bullet just enough into the case to hold it in place, and then carefully close the action on it. Take that out and measure it with your caliper. That will give you a contact measurement for that bullet. You will need to do this with every different bullet you shoot. There are tools you can buy to make this a little easier, but this will work. I would recommend you try it at least twice to make sure the bullet is sitting in the same spot. Sometimes, if the neck is sized too much, the bullet will be slightly jammed into the riflings and will pull out when you remove it giving you a false measurement. Ive seen loads that were shooting patterns go to shooting little groups just by changing the seating depth. As you seat bullets closer to the riflings your pressure will rise too. Need to watch that. For hunting loads I generally start about ten thousandths off the rifles and go back in increments of ten thousandths. I wouldnt run the risk of seating a hunting bullet to touch, but for target shooting those will shoot best in alot of rifles.

Deleted User · 04-23-2003, 09:26 AM

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handloader1 · 04-23-2003, 10:17 PM

The best way to do it is with the right tool, but this how I did it before I obtained a Stoney Point Overall Cartridge Length (O.A.L.) Gauge. I would pick the most uniform bullet I could find in the box of bullets I was going to load. I would place just the bullet in the chamber and very very very so lightly tap it into the rifling so it will just stay there. I would then set the rifle on it' s butt, and place a wood dowel or cleaning rod down the muzzle contacting the tip of the bullet. I then would place a very thin mark around the dowel buy rotating it. I would then tap the bullet out and reinstall the bolt, reinsert the dowel, and make another thin circular mark around it. I then removed the dowel and measured the differnece between the two lines with a dial, or eletronic digital caliper and that was my O.A.L. It is not as accurate as using a Stoney Point O.A.L. Gauge but it is pretty close. Good luck.

mounting man · 04-24-2003, 02:12 PM

I' ve doe it,as Handloader 1 did,but used a steel rod. As he has stated,it works OK.
Where you run into discrepancies,the bullets are seldom all the same length{tip to base].

handloader1 · 06-09-2003, 09:47 PM

george_s:

Take a look at this string. Good luck.

stubblejumper · 06-09-2003, 10:07 PM

Being closer to the rifling does not always result in the most accurate load.You have to experiment to see what works best in your gun.I have one gun that shoots consistant 1/2" groups and the bullets sit .220" off the rifling.The throat is long so this is as close as I can get and still fit the magazine but since the accuracy is so good I couldn' t care less.I have another rifle that shoots best with the bullets .070" off the rifling and it too shoots consistant 1/2" or better groups.

soarkrebel · 06-09-2003, 10:32 PM

I use the stoney point OAL tool also. great investment!

before i would seat a bullet as described and paint the bullet with permanent magic marker. chamber it and do this until no land and groove scratches . took a long time.
the stoney point oal solved that problem.

neweboarhunter · 06-10-2003, 12:23 AM

I like the Stoney Point system. I have just started using it. I use a wooden dowl rod to feel the bullet hit the lands. Also stoney point will make a leangth gauge for any caliber if you send them a brass case they will modify it.