What do you guys think about that? What he said makes some sense. I don't know if I put much stock into alot of articles in
handloader, there groups are less than impressive. I have yet to see any guns tested with .5" groups at 100 yards. But makes for
interesting reading.
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Larry
I have owned a lot of bench rest style rifles in calibers such as 6mm/06, 270, 7mm Rem and 300 Win and they have had standard chambers done with JGS reamers and reloaded with standard dies.
The following is what I have found in general, that is, some exceptions.
The most consistent accuracy has come when cases have been full length sized so as to produce about .003" headspace. Less is not good becuase press sring means that cases will zero headspace and others might have .001 or .002. Accuracy seems to go off once headspace goes bigger than about .006".
In general cases sized to produce a abut .003" headspace shoot better when the bullet is back from the rifling and neck sizing general shoots better when bullet is just near or just on the rifling.
When cases have about .003" headspace, if the bullet is seated too deep the open triangle groups occur. As the bullet is seated out the groups come down in size. Once the bullet is seated out too far the groups start to get flyers.
By the way, some of the best groups that come from bench rifles in 6mm PPC is when fireforing cases.
An advantage to having cases sized for a few thou headpsace is that you can usually get the same point of impact with bost new and resized cases.
One thing to remember about true bench guns, is that the chambers and dies are all concentric but this does not apply to ordinary rifles.
My experience has been that partial full length sizing is not the way to go. However, I have not altered seating depth when I have tried partil full lenght sizing and it may well requirea different seating depth than is the case for either neck sizing or full lenght sizing that produces a a few thou headspace.
One of the good things about ammo that is sized to produce a few thou headspace is that the seating depth that is best is commonly for the standard OAL for the caliber. In fact Hornadies usually shoot best when seated to the cannelure. This is good when considering magazine lenght.
One disadvantage to sizing that gets a few thou headspace is that the ammo can lose accuracy if kep for some time. This also applies to cases that you size today but don't load for sometime. This occurs because the most accuracy usually comes with the bullet seated back from the rifling and with time the brass loses neck tension and you also get variation in neck tension with time passing. When the bullet is back off the rifling neck tension is more critical to accuracy than whej the bullet just near or just on the rifling. New brass does not seem to sufferer from this.
Mike
Very interesting post--especially the part about older rounds. I wonder if running older rounds through a Lee Factory Crimp die would "rejuvinate" the eveness of the neck tension.
Frankly, I like neck sizing because I'm lazy. A quick spin in the moly coated shot, and run the brass into the TiNi coated bushing, and VOILA. No messy lube, very little pressure, etc. To "clean" my brass I just twist the neck area with some steel wool, then I have an old bronze brush wrapped with steel wool attached to a bench mounted drill that cleans/polishes the inside of the neck. Now the neck is all clean and smooth and ready for sizing.
R