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Old April 27, 2011, 11:25 PM   #1
mkelly9779
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280 Rem BDL Loading Question

I have a reloading question about an issue that I haven't run into before. I was reloading some 140gr noslers for a remington 700bdl with a synthetic stock the length of the COL needed to be less than the book called for. The book calls for 3.330 COL and I had to load it to 3.316 to keep it out of the rifling. Has anybody else run into this? Most loads I have tried to develop I had to push it out farther than what the book calls for to get it close to the lands.
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Old April 28, 2011, 03:16 AM   #2
Eagle0711
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Good observation. Sounds like your rifle has a short distance ( leade ) to the riflings. I woulg leave about .010" jump to the rifling. You can adjust it to find the best spot for the most accurate. I wouldn't have the bullets against the riflings because it will run up pressure.

Iv'e read that a few manufactures are machining very long leades in their guns because of problems with hot loads. In the old days when a gunsmith would re-chamber a 30:06 to the 308 Norma Mag. it was standard practice to put 3/8" of freebore to keep pressures down.
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Old April 28, 2011, 12:06 PM   #3
Unclenick
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This issue comes up periodically. The load manuals usually give you the SAAMI maximum COL for the cartridge. That number is just a not-to-exceed number if you want the rounds to fit in a SAAMI compliant magazine designed for the cartridge in question. It has nothing to do with fit in the chamber, and it also has no minimum.

The COL you need to load to has to do with bullet shape. If you have a bullet with a very long ogive, it will stick out further, making the COL longer than one with a very short ogive does when both are touching the lands. If you think about it you'll realize that all bullet ogives would have to be the same length for all to be seated to the same COL and be the same distance off the lands.

The illustration below shows two bullet styles loaded to the same distance off the lands, but you can see how different the COL's are. Most modern round nose bullets are not like the one I've drawn there, which I did to exaggerate the principle. Most have a tapered ogive between the bearing surface and the start of the nose spherical sections so they can get nearer the maximum COL and not steal too much powder capacity from the case.

I also added an illustration of parts and terms to do with bullets and cartridges just in case you're new to talk about ogives and bearing surfaces and whatnot.



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File Type: gif Bullet and cartridge terms final size.gif (56.9 KB, 394 views)
File Type: gif .308 chamber 3.gif (41.4 KB, 184 views)
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Last edited by Unclenick; April 28, 2011 at 01:47 PM.
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Old April 28, 2011, 04:57 PM   #4
homesick
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I just ran into the same thing with a 700 Rem VLS 223, Sierra bullets are OK but I had to seat sub COL with Hornady. These are 50/52/53 gr bullets. I just figure it is what it is and go from there. All bullets shoot very well when seated off the lands but I did build a bit of pressure with the Hornadys when seated at Max COL wasn't very accurate either.
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Old May 1, 2011, 12:40 PM   #5
mkelly9779
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Do you have to adjust your powder loads much from what the books says? I would imagine when you push the bullet farther in it would increase the casing pressures. Would it be significant enough to worry about?
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Old May 1, 2011, 02:35 PM   #6
Unclenick
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The below is from data in the U of M study from 1965. Notice that either too far in or too far out raises pressure. That's why it's best to figure out what seating depth your gun likes with the bullet using starting loads first, then work up to final charge, watching for pressure signs.

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File Type: gif seating depth v pressure.gif (12.3 KB, 1106 views)
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