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Old June 24, 2011, 12:23 AM   #1
Kayser
Senior Member
 
Join Date: May 29, 2002
Location: Illinois :(
Posts: 550
Hornady 150gr bt-fmj. Oal and cannelure issues.

This seems to pop up in various places on the internet, and I have yet to see a definitive answer.

The Hornady 6th edition manual lists an OAL of 2.780" for 150gr bt in 308 win. When you seat to this depth, the cannelure is way outside the case.

Many people have noticed this. There are a number of threads out there, with advice ranging from

- "seat to listed OAL. ignore cannelure"
- "seat to cannelure"
- "I've talked to Hornady and they said the 2.780 is an error"
- "The newest hornady manual lists 2.700"

Anyway, here's an assortment of threads on the subject

http://thefiringline.com/forums/showthread.php?t=264416
http://www.thehighroad.org/archive/i.../t-555089.html
http://www.ar15.com/archive/topic.ht...&f=42&t=322515
http://www.gunandgame.com/forums/pow...nual-data.html

In that last one, the guy claims he ends up in the lands at 2.72" which also seems crazy to me (that can't be right, can it?). I personally have had a few cartridges of this load (3 out of 100?) fail to close the bolt at 2.78" for reasons I could never determine.

For me, the kicker is this. Of the rounds I've shot at this load (several dozen at 41 gr 4895, 2.780" oal) quite a few of them give mixed pressure signs. I get a lot of backed out primers (0.01" in the extreme case) indicating low pressure. But I also get some minor flattening from time to time, indicating potentially high pressure. I load right in the middle of the range : about 41 gr). So, clear as mud, I guess.

I'm tempted to just seat at 2.73, where the cannelure just reaches the mouth. But I honestly don't have a good feeling after all these years for how dangerous that sort of thing is. Some people seem very cavalier about playing with lengths. I'm paranoid

Does anyone actually have the 8th Edition Hornady manual? What OAL do they list for the 150 gr bt-fmj? If you have one of these bullets handy, how long are they? The ones I've got are 1.12"

Thanks for any expert advice, gurus.
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