.30-06 load development, bullet seating depth

[Walkalong]

Backing that up is how many heavy for the caliber match bullets are seated well below the neck/shoulder juncture and shoot extremely well.

Although many years ago I heard the same thing, that seating deep below that juncture was "bad".

 

[Bart B.]

Then there's the "caliber depth" bullets are seated in case necks; whatever that means. I come up with 3 different ways to measure it that result in 3 different OAL's for a given cartridge with some bullets.

 

[Walkalong]

Then there's the "caliber depth" bullets are seated in case necks; whatever that means.

Well, for general shooting, I still like that one.

 

[sage5907]

Some of the comments on this thread don't take into consideration the shortness of the bearing surface of a Sierra 150 grain boattail Gameking. The length of a 30-06 case neck when the case is trimmed to 2.484 is .375. The boattail of the Sierra bullet is .175 in length. So, when the bullet is seated flush with the back of the neck there is only .200 of the bullet actually touching the case neck. This is far less than the caliber length of .308 that was discussed above. If you try to seat to the lands this .200 becomes shorter to the point that the case may not grip the bullet enough to prevent problems. This could be OK for a target shooter but not Ok for a hunter.

 

[Bart B.]

Well, 30 caliber 150-gr. bullets seated in 30 caliber cases with only about .150" of bullet body gripped by case mouths don't shift for all 8 rounds fired in Garands.

I've seated Sierra 168's and 180's that shallow in .308 cases and shot them in Garands with max loads; last round chambered had no bullet shift after 7 heavy recoil cycles. Decades ago, folks shot 180's seated in 30-06 match ammo cases the same amount and their Garands didn't shift them either.

Done the same thing with 168's in .308 cases shot from bolt guns; last round in the magazine has no bullet shift.

Do your own tests and see what happens.

Measure the bullet pull in pounds; that's what counts and it's the industry standard. Check the case neck length that grips 7.62 NATO M80 ball ammo's 148-gr. bullet behind its cannelure. Specs for its bullet pull (release force) is 60 pounds.

 

[sage5907]

Case neck tension varies greatly depending on whether the case is old and hard or newly annealed or a new case which is soft. I keep my case necks really soft so I can seat a bullet with just a slight pressure on my thumb. I would rather have a soft case neck seated at .200 of bearing surface than a hard case neck seated at .150. I would think the soft case neck would give a more consistent group.

 

[Bart B.]

Yes, soft case neck (low release force or neck grip) is good. Muzzle velocity spread and standard deviation is smaller. I use as little as possible for single round loading. No more than 2 to 3 pound release force.

Sometimes military teams would use a Lyman 310 nutcracker tong tool to seat M72 or M118 match ammo bullets about .010" deeper. That broke the black asphultum seal between bullet and case neck. Bullet release force went from about 40 pounds to about 7 pounds. Vertical shot stringing at long range was reduced by 25 to 50 percent.