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Old 01-16-2008, 08:03 AM
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Question .308 seating depth

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Just started loading for .308 using BL-C2 (45grains) and noticed that the minimum and maximum oal length is 2.800" I am using Hornady 150 GR SST interlock bullets (boatail may contribute to a little less pressure?). I have noticed that when I seat at 2.800" I am not even close to the grooves. I am using the Lee Factory Crimp Die so I guess I should not worry about it? I called Hornady and they said that I can seat it down to the groove as long as I don't approach max charges (48 grains). Does anyone have any experience with this combination of powder and bullet? I plan on shooting these bullets in a semiauto. 2.800" seems a little long.
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Old 01-16-2008, 08:25 AM
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Here's how I usually approach the issue:

I first load to the book-recommended OAL, measuring from the cartridge base to tip of bullet. I check the first round to see if it fits in the magazine, then feeds, chambers and extracts freely. If so, proceed at that length. If not, adjust shorter so that the loaded round DOES feed and chamber. Ideally, I like to have the bullet base even with or above the base of the neck, if that corresponds to the book OAL.

After I find the best powder and charge for that bullet at that length, I'll slowly seat it deeper to see if there's a best or better seating depth for accuracy. I'll use increments of one-half turn on the standard threaded seating stem, or .005" with a micrometer style.

Once I find the best seating depth, I use a caliper to mark a bullet at bore (not groove) diameter - .300" for a .30-caliber, for example. I measure the distance from that line to the cartridge base, and record the number.

If I change bullets, I score one the same way and set its seating depth to the recorded number. That gives me the probable best seating depth for the new bullet, without experimenting.

Note: at NO time did I ever measure, know or care about "distance to lands." Don't need to - ever.

Here's a round, marked at bore diameter, as described.
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Old 01-16-2008, 09:26 AM
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Location: Eastern Oregon
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Also if you go longer or shorter you will get higher pressures so you will need to watch for that also.

Same as above but I go off the lands. Have the Hornady OAL gauge so it's pretty easy that way, but on that I think I only have one gun that is out to the lands the rest are a lot shorter OAL. I basicallly go off what gives me the best accuracy and still goes in the magazine and will cycle without problems. A lot of times the cannalure on a bullet will not be my best crimping point. If I setting up to just blast out of an AR I adjust my powder accordingly so that I can crimp in the grove.

The grove is basically generic that bullet (maybe not that exact bullet) was designed for a 30-06 or 300sav the crimping grove would match to that case set at the bepth recommended. Even if not in the grove I would try with and without the FCD. there should be enough neck tension to hold the bullet without it. You might find that it shoots better or worse with or with out crimp.
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Old 01-16-2008, 09:27 AM
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wow, thanks for the reply. Good to know about the lands, always wondered about the "lands" deal. I hope that the rounds will feed. Got a little happy pulling the progressive press and stopped at 40 rds. I might have to change powders since this BL-C2 does not give any ranges to deviate at all. Had alot of this powder for .223s.
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Old 01-16-2008, 09:44 AM
Rocky Raab's Avatar
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BLC-2 is a fine powder for both the 223 and 308 (it's surprising how many powders work well in both). As I wrote, I ignore the lands completely. I used to try to measure them, using smoked bullets, cleaning rods and all sorts of half-baked methods. Tried a Stoney-Point gauge and an RCBS gauge and got "answers" all across the board with both. Gave up and found my current system, which is simple, repeatable and doesn't need to know where those pesky lands are.
To see my books and articles, just Google my name.
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Old 01-17-2008, 05:56 AM
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Our loading manuals have only recently started giving OAL numbers, without mentioning that it is only a suggested starting point as is all the rest of the data. So, suddenly, OAL has become a major point of confusion to newbies. I wish they would just delete the OAL and go back to telling folks how to properly find and use seating depths to change the ballistics of a load.
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Old 01-18-2008, 04:42 PM
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I read the COL for that bullet at 2.735" from the Hornady manual. The powder you are using is not listed. I am with the Hornady rep, If the charge is not compressed and you have a listed load for that powder and bullet you should find something that works.
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Old 01-18-2008, 06:46 PM
faucettb's Avatar
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For a hunting rifle I'm with Rocky on the "lands" deal. If it won't feed thru the magazine then it's not really a hunting round. Rule of thumb for seating is seat at least the caliber deep, i.e. quarter inch deep for a 25 caliber bullet and so on.
Bob from Idaho
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