seating depth question

[MildBill]

I am still relatively new to metallic reloading... so this question may seem kind of dumb to some of you...

As I understand it, the rule of thumb is you want the bullet seated at least as deep as the bullet's diameter.

My question is, do you want that much of the bullet's bearing surface seating below the case mouth,

or in the case of a boat tail bullet, if the total depth seated, including the boat tail, is at least equal to the diameter of the bullet but the amount of bearing surface below the mouth is less than the diameter of the bullet is that meeting the rule of thumb?

Thanks.

 

[watercam]

For hunting or any rifles that load out of a magazine I try and keep about a calibers worth of bearing surface (that is excluding the boat tail) supported by the neck of the case. That said I have had as little as one half that in match rifles with good accuracy. I once fed a cartridge with half a calibers worth into the chamber, removed it and checked the bullet run out and it was still true. For mag fed cartridges I use .003" neck tension.
For single loaded cartridges (usually Long Range where utmost accuracy is required) I feel it is more important to use the most accurate seating depth for that rifle. I use only .001-.002" of neck tension on Long Range rounds and may only have them seated 1/3 of a cartridge diameter into the neck. One can adjust the length of the leade thereby enabling one to seat bullets into the lands but still be supported well. Talk to your gunsmith about that.
I can not speak for the Benchrest crowd as I am a coat and sling shooter but using the above guidelines I have had good success.

 

[necchi]

Mild Bill, it is a rule of thumb and that's it, generally excluding the boattail.
But when I began loading I quickly tossed that rule out the window, and go as little as .125 in the case (non-benchrest) in several different calibers. Bench rest guy's with custom chambers can go with even less.

This is really the rule;

For single loaded cartridges (usually Long Range where utmost accuracy is required) I feel it is more important to use the most accurate seating depth for that rifle.

However there are several issues when searching for seating depth. As mentioned, there is a difference between Hunting loads and Bench Target use. The hunting load needs the stability for added rigors of in field use, that's a time when I want the caliber depth seating.

But when seating long like that the actual trouble is "concentricity" or the bullet being straight in line with the case neck and bore, I think that's where the rule cam from, having more in the case can help keep things straight. If you have the dies set properly and the tools to check concentricity or runout as it's called, you can be kept under control and seat a little longer IF that length improves accuracy.
Of course with magazine feed rifles, the Magazine length is a determining factor.

Watercam also mentioned neck tention, a whole nuther can of worms,,