Benchrest in Canada
BR Discussions => Centerfire Discussions => Topic started by: South_Pender on June 04, 2017, 11:41:08 AM
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Is there an agreed-upon opinion about the minimum distance that the bullet should protrude down into the case neck? I ask because I've discovered that the new-to-me Sako 6 PPC I'm loading for seems to have a long throat, and to seat the bullets I want to use so that they touch the lands (68-gr. Bart's and 68-gr. Watsons) puts the bullets out so far as to give me less-than-usual bullet/neck contact (less than half the length of the neck). Of course, I could seat them deeper, but this would introduce a certain amount of jump, which I'd like to avoid if possible.
With the Bart’s touching the lands, the base of the bullet is .121" down the neck. The Watsons end up about .140" down the neck. I don't plan to work rounds through the magazine, so getting the OAL to work through the mag is unnecessary. I'm using the Wilson chamber-type straight-line seater (and the Wilson chamber-type neck sizer as well). I’m wondering whether this amount of contact (like the .121” with the Bart’s) will produce enough tension and I’m concerned about creating excessive run-out.
Any insights on this?
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The amount of bullet in the neck is not a real big concern. With powders like N-133 which seem to like lots of neck tension on the bullet to aid in pressure curve, may be a slight issue.
As you are not using the magazine to feed, I would not worry about the amount of bullet in the neck, just feed the rifle what it shoots well.
If the bullets are flat base you should be fine, a boat tail will have less neck grip due to the reduced bearing surface.
With the dies you are using you should still be able to make minimal runout loads.
I once had a 40XBR that had .010" of bullet grip on a .223 50gr Berger bullet.
It shot pretty good.
You may find that your rifle may like a wee bit of bullet jump, so do test that option.
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And it leaves room for more powder !
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My old Sako 6ppc would shoot 55g Nolser Ballistic Tips as good as any match bullet if you'd believe it. Or at least as good as Opel's early 6mm batches. :D They were seated so shallow that if I looked at the loaded rounds the wrong way, the bullet would pop out of the case mouth. I seated them there because that's the OAL it took to touch the lands of the factory barrel with such a short bullet. If seated deeper, the groups would open up.
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One thing you should be aware of with those Sako mag fed rifles is that you won't be able to just place a round on top of the feed lips and close the bolt. The bullet nose will jam up on breach face. I used my old Sako for several years in matches at Rosebud and I had to seat each round in the mag before closing the bolt to prevent stoppages. You could thumb in a round a little deeper so the bullet nose is inside the chamber. Either way, both eat up time on the clock and I found seating a round in the mag was the fastest and most repeatable process during competition.
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Thanks a lot, guys. Your comments have been extremely helpful. I will now stop worrying about the shallow seating and hope that the Bart's and Watsons shoot as well as they're supposed to. In my reading, I ran across reference to Berger "column" bullets. I must confess that I don't fully understand the principle behind them, but thought I'd pick up a box of the 64-gr. 6 mm. bullet.
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As I understand it , The idea of the column Bullet is to go for optimum lead
Line (percentage ) and not a specific target weight . They shoot well and are a decrnt Bullet