How far to set a Barnes X Bullet off the lands (7mm-08)?


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Macchina
December 30, 2008, 11:13 AM
I am working up some X bullet loads for my 7mm-08. I am using 140 grains with Varget. I was wondering what OAL I should start at...

Also, If you shoot this bullet with Varget, how much do you use?

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Varminthound
December 30, 2008, 11:53 AM
I always go by Barnes advice to seat their bullets which
.050" off the lands. So determine the assembled round length to the lands and subtract .050". I don't go by OAL as much as the length to the ogive. It seems that there is inconsistency in the bullet length from all manufacturers (measure a few with a caliper).

Hornady has a tool (formerly by Stoney Point" for measuring the length of a bullet to the ogive when it touches the lands. I find a better consistency in results by loading based on ogive length but then I get anal about loading.

As for the amount of Varget that depends. What 140 bullet are you using. Their manual has their work ups. Since the bearing surface (part of the bullet that gets engraved by the rifling) varies by manufacturer and by bullet within each manufaturer I buy their book and work up from their minimums. More bearing surface means higher pressure. Is the Barnes bullet you are using coated? That makes a difference.

Read up and work up slowly. Watch out for pressure signs.

At one time some people didn't like Barnes accuracy. Those problems have been cured.

Good luck and have fun.

mhank55@gmail.com
December 30, 2008, 12:08 PM
use a felt tiped marker on the bullet. Stay back .002 Abolt3006

rcmodel
December 30, 2008, 12:11 PM
Depends on which X-bullet you are talking about. They have three different ones now in 7mm.

But I would start at what Barnes says to start at in their reloading manual.

Failing that, I would use this.
http://www.barnesbullets.com/images/7mm-08RemingtonWeb.pdf

rcmodel

GooseGestapo
December 30, 2008, 12:38 PM
Also, magazine length will determine max OAL, if you're going to hunt with them.

My Rem. M7 will not take over 2.830" in the magazine. However, it has a short and tight chamber. Max to grooves with a Nosler Part. is 2.805", but I seat them to 2.795" for positive chambering and feeding. The Rem. 140gr CorLokt's touch at 2.830", but I too, seat them to 2.800", same a factory ammo. Oddly, the Sierra ProHunter and GameKing bullets will touch lands at 2.795" and are most accurate at 2.775"OAL, hence they are my "favorite". Besides the 139gr BTSP Hornady's. These due to short bearing surface can be run to ~150fps higher velocity by slighty higher powder charges and near equal accuracy.

Barnes recommends seating .050" off the grooves. If that will fit your magazine, use that. I use to "old method" of measuring a fired case with a dented case mouth and the bullet lightly seated by chambering it. Then measure OAL. You can/should coat the bullet with a magic marker to see the total length seated as extracting the "cartridge" can cause the bullet to be dislodged......

The recommendation by Barnes is due to "unyeilding" nature of "solid" alloy bullet causing pressures to be somewhat higher than that encountered by "conventional" cup and core bullets.....when seated to touch the lands.

Macchina
December 30, 2008, 01:15 PM
I am currently loading 140 grain Nosler BT's over 41 grains of Varget. To determine OAL, I usually load a dummy round with weak neck tension, then chamber it in the rifle I am loading for. Using calipers, I measure the OAL: this is the distance to the lands. I then subtract (usually starting at .02" for normal bullets) to get my gap distance. The reason I ask how far I should seat the bullet, is because I read that x bullets are different, both in seating depth and powder charge. I am using the original X Bullet.

.05" sounds like a good starting point.

Now for how much Varget...

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