Ogival Seating depth questions: min/max for bullet and magazine


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WinchesterAA
March 27, 2013, 01:00 AM
So I finally got around to making a comparator and modifying a case to act as a COAL gauge for my future 308 loading. (No press or powder yet)

RIFLE SPECS:
Remington 700 AAC-SD 20" barrel, 1/10" twist rate
Minimum seating depth for fitting in the magazine: 2.820" head to tip

Since my barrel's twist rate is on the faster side, I thought I'd start with 180 grain and 200 grain bullets just to see what I could do with them.

MEASURING TO TOUCH THE LANDS
180 grain COAL measurements from the head to ogive:
Min: 2.358"
Max: 2.361"
Avg over ten measurements: 2.359"

200 grain COAL measurements from the head to ogive:
Min: 2.378"
Max: 2.384"
Avg over ten measurements: 2.381"


My questions are:
With the 180 grain bullet seated such that the OAL from head to ogive is approximately at the lands, the actual seating depth is less than 1/10th of an inch (not counting the boat tail portion which doesn't contact the case neck). That's much too little, right?

With the 200 grain bullet seated such that the OAL from head to ogive is approximately at the lands, the actual seating depth is approximately .22", which is less than the occasionally recommended "caliber depth" minimum, but should still be OK, right?

With the 200 grain bullet seated at the minimum COAL from head to tip to fit in the magazine (2.820"), the actual seating depth is about .360" which puts the base of the boat tail about 1/10" below the shoulder of the case. Is that bad? How far past the shoulder can you go before causing a problem?

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243winxb
March 27, 2013, 10:10 AM
My questions are:
With the 180 grain bullet seated such that the OAL from head to ogive is approximately at the lands, the actual seating depth is less than 1/10th of an inch (not counting the boat tail portion which doesn't contact the case neck). That's much too little, right? Yes, to little.

With the 200 grain bullet seated such that the OAL from head to ogive is approximately at the lands, the actual seating depth is approximately .22", which is less than the occasionally recommended "caliber depth" minimum, but should still be OK, right? No, on loading the bullet can be moved out of alignment if it hits anything. Should be ok if not loading from the magazine.

With the 200 grain bullet seated at the minimum COAL from head to tip to fit in the magazine (2.820"), the actual seating depth is about .360" which puts the base of the boat tail about 1/10" below the shoulder of the case. Is that bad? No, a litte is ok. Just look at the 223 with a 68gr bullet seated. Way below the neck/shoulder junction.How far past the shoulder can you go before causing a problem? To far, is when the bullet falls into the case on seating. Seating depth is not a problem when using a starting load of powder & working up.
Question 3 is the better COL. Try to keep the base of the bullet (full diameter, not BT) at the neck/shoulder junction. Where the bullet is in relationship to the rifling has very little to do with accuracy. IMO.

MtnCreek
March 27, 2013, 10:58 AM
What type bullets and what are you planning to use them for?

Don't worry about jump to lands. Most bullets are not very sensitive to it. Load to reliably feed from the mag.

Seating the bullet deep will increase pressure, but as long as you're slowly working up a load, it won't be a problem. FWIW, I'm loading some .308 w/ 208 amax seated to fit a mag (~2.900 OAL). The base of the bullet is WAY below the shoulder. The ogive is getting pretty close to the case mouth.

Walkalong
March 27, 2013, 11:06 AM
Wring out what the gun will do with the rounds loaded to fit the mag and see what it does. It may surprise you. Seating to or into the lands is better left to guns with chambers cut to dimensions with less freebore.

243winxb
March 27, 2013, 12:10 PM
Seating to or into the lands is better left to guns with chambers cut to dimensions with less freebore. +1 Like in a custom chambered barrel.

USSR
March 27, 2013, 12:57 PM
Seating out to the lands with a factory Remington barrel is a fools errand. ;)

Don

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