Minimum Seating Depth / Max COL (.30-06)

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lineofsight

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Did the marker on the bullet, into the case, into the chamber and measure approach to determining seating depth / distance to lands. Case left scrape marks on bullet so not concerned about bullet being pulled out of case (can see how deep it went in) and yes will repeat this process a couple more time but...

Factory Winchester .30-06 measures 3.15, also listed as min. COL in the manual.

Measured length to lands 3.39, pretty darn close to the 3.40 headspace listed in the manual. This produces a seating depth of ~.25 which seems shallow. Also seats no where near cannelloni (cannelure whatever).

Dummy round feeds from mag, chambers, and extracts no issue there.

Am a little hesitant about the .25 different in overall cartridge length and .25 seating depth. Thought would want at least .31 depth as the bullet diameter is .308. Difference in seating depth of .25 from factory also changes fill ratio.

Comments, concerns? What do you say?

EDIT

Rifle is a Remy 700 SPS DM
 
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Just sounds like a long throat. I had a 30-06 that I couldn't get anywhere near the lands with standard cup and core bullet. It was a very accurate rifle though, one of Gatehouse's buddies is killing bears with it now.
 
Could well be long throat - where would you suggest seating bullet / min seating depth? Or does come down to loading a batch at 3.2, 3.25, 3.3, 3.35 (and no further to remain .3 in the case) and see what happens?
 
Do I have any concerns? That depends on what your load is for.

I wouldn't want a big game load that had so little bullet shank in the case neck for fear of the bullet becoming stuck in the chamber throat and dumping powder into your action when you are attempting a fast follow up shot. This is even more problematic if your bullet is a boat-tail design, due to even less less shank contact with the case neck. For target shooting or varminting a fellow can take time to eject the round carefully and accuracy in such activities trumps most other considerations, but not so when big game hunting. Big game hunting's first requirement is that the ammo is 100% reliable. For this reason I always seat to the cannelure, and crimp to uniform the bullet pull. After reliability comes terminal performance, then in flight performance; so as you can see any small advantages in accuracy gained by adjusting the seating depth is fairly far down the list in importance when we are considering a big game rig.

With consideration to pure accuracy, unless the bullet is pushed firmly into the lands, with so little shank to neck contact, it is possible that the bullet will not enter the bore squarely. This is more detrimental to accuracy than any perceived advantage of seating the bullet so long. Consider that the serious accuracy bug will check the runout of the bullet nose as well as the case neck. The rule of thumb at one time was to have a caliber length of bullet shank in contact with the case neck, but admittedly with some bullet designs this is all but impossible, it is still something to consider.
 
Barnes states that bullets should be seated a minimum of 2/3 calibre.

.308 x 2/3 = 0.203"

FWIW I have some .308 loads that are .040 longer than listed COL. Cannelure is way out there, but still have .23 in the neck, and I'm .015 off the lands. No problems.
 
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