"just off the lands..." - Page 2

Horseman · March 10, 2011, 11:44 AM

Quote:

All this talk of measuring distance to the lands, and no one mentions "candling"?

Candling is more fussy and less precise than chambering a bullet in a dummy case and measuring it IMO.

cdoc42 · March 11, 2011, 04:37 PM

The problem with chambering a dummy round and measuring the overall length is the tip of the bullet doesn't touch anything - it's the ogive that engages the rifling. If you have a soft lead tip bullet and you damage it in any way as you reload, your measurement is skewed, especuially if you are planning on being 0.01 to 0.02" off the lands. Not to mention, a different lot number of the same bullet from the same manufacturer can have the ogive in a slightly different place - may be just a manufacturing tolerance problem. I've seen it with Remington and Hornady bullets - rarely with Nosler - it's a big factor with Barnes which is why, I think, they don't recommend seating close to the lands.

You can use a Stoney Point Comparator which attaches to your caliper and has inserts specific for calibers. This will allow you to measure the finished round from the ogive to the base of the case. Every bullet you load for your caliber should be measured, e.g., 150gr from Hornady and from Sierra are likely to have a different ogive, so that seating each 0.01" from the lands will give you a different overall measurement.

Here's the technique I've used for 30 years: Withdraw the bolt from the rifle and drop your bullet into the barrel; tap it LIGHTLY against the lands. Insert a cleaning rod from the muzzle until it touches the bullet. Make a half circle mark on the cleaning rod at the muzzle with a fine-tipped "Magic Marker." Tap the bullet out. Seat the bullet into a resized case, at a length longer than you expect it should be. Chamber this dummy round as has been described by others herein. Reinsert the cleaning rod and mark a full circle mark on the rod. If the bullet is at the same location on the lands as your original bullet, your seated round is at the lands and you will have only one black mark circling the rod. If there is any gap between the half-circle and complete circle you need to repeat the chambering process. Assuming there is only one circle, you now measure that dummy round with the Stoney Point comparator and you have an overall measurement from the ogive to the base. You then seat the bullet 0.01 to 0.02" deeper and start experimenting. You cannot use this mesasurement for all other bullet styles; as I said, the ogive differs in location which may explain why if you loaded all 150gr bullets to the same overall length (tip to base) you'll a difference in accuracy.

March 11, 2011, 04:37 PM	#27
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	The problem with chambering a dummy round and measuring the overall length is the tip of the bullet doesn't touch anything - it's the ogive that engages the rifling. If you have a soft lead tip bullet and you damage it in any way as you reload, your measurement is skewed, especuially if you are planning on being 0.01 to 0.02" off the lands. Not to mention, a different lot number of the same bullet from the same manufacturer can have the ogive in a slightly different place - may be just a manufacturing tolerance problem. I've seen it with Remington and Hornady bullets - rarely with Nosler - it's a big factor with Barnes which is why, I think, they don't recommend seating close to the lands. You can use a Stoney Point Comparator which attaches to your caliper and has inserts specific for calibers. This will allow you to measure the finished round from the ogive to the base of the case. Every bullet you load for your caliber should be measured, e.g., 150gr from Hornady and from Sierra are likely to have a different ogive, so that seating each 0.01" from the lands will give you a different overall measurement. Here's the technique I've used for 30 years: Withdraw the bolt from the rifle and drop your bullet into the barrel; tap it LIGHTLY against the lands. Insert a cleaning rod from the muzzle until it touches the bullet. Make a half circle mark on the cleaning rod at the muzzle with a fine-tipped "Magic Marker." Tap the bullet out. Seat the bullet into a resized case, at a length longer than you expect it should be. Chamber this dummy round as has been described by others herein. Reinsert the cleaning rod and mark a full circle mark on the rod. If the bullet is at the same location on the lands as your original bullet, your seated round is at the lands and you will have only one black mark circling the rod. If there is any gap between the half-circle and complete circle you need to repeat the chambering process. Assuming there is only one circle, you now measure that dummy round with the Stoney Point comparator and you have an overall measurement from the ogive to the base. You then seat the bullet 0.01 to 0.02" deeper and start experimenting. You cannot use this mesasurement for all other bullet styles; as I said, the ogive differs in location which may explain why if you loaded all 150gr bullets to the same overall length (tip to base) you'll a difference in accuracy.