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Old September 15, 2000, 06:59 PM   #6
Jack Straw
Senior Member
Join Date: July 26, 1999
Location: Georgia
Posts: 362
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by labgrade:
JS, = "experiment by reducing the OAL by .01" increments ... "

That sounds like quite a bit, especially at (if) a max load. In many instances, just a .005" change can improve accuracy - towards or away from the lead.

I would suggest that if you are going to change seating depth by .01", I'd back off at least 5% max & work back up - safety first & all.

Many times you can't seat bullets out to optimum length as the magazine won't allow the longer OAL ....

I guess I should have elaborated. I reduce OAL by .01" increments until I get down to the length listed in whatever manual I happen to be using. I then take the best group's OAL and try shooting at .005" above and below that length to see if I can improve group size. I do this just because it cuts down on the total number of shots needed to find the optimum OAL. I started doing that upon the advice of a Sierra technician a couple of years ago. I would think that this would be safe as long as I don't go below the published OAL; is there some error in my thinking? I don't mind changing a practice for the sake of safety.

That's definitely true about a magazine limiting the OAL. I have run into that several times. It is not necessarily an accuracy problem though. The same Sierra tech mentioned above explained to me that top accuracy is frequently found with the bullet nearly touching the rifling. As the bullet is seated further into the case, accuracy will drop a point. He stated that there usually is another seating depth at which the accuracy will return and then diminish as the bullet is seated even deeper. At that point, I try varying the depth by .005" just to see if tweaking the OAL improves group size even further. My shooting has pretty much supported what the tech told me.


[This message has been edited by Jack Straw (edited September 15, 2000).]
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