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While testing my 270 hand loads of 130 gr. sierra btsp with 59.5 gr of h-4831hs I noticed the velocity kinda low(2860fps from my 22 inch barrel rem) I neck sized with no crimp using Lee collet dies. Does neck sizing and not using a crimp affect velocity? I really shouldn't complain becouse my groups were running from 3/4 to 1 1/4 at 100 yds.
 

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Tony,

It's funny about the .270 Winchester. I've read several times where handloaders like yourself were surprised by the lower-than-expected velocities for their ammo. I don't know what it is, perhaps the factories are "embellishing" their ballistic tables. I don't know for sure.

Regardless you may be on the right track regarding your choice of dies. I really like the several sets of Lee Collet Dies in my possession but they do not squeeze the necks much. Great for case life but maybe not so great for top velocity. I think a uniform crimp like that provided by the Lee Factory Crimp Die will help you increase velocity and possibly accuracy a bit, although this load certainly does well on that account already.
 

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About those Lee Collet dies.  I too will agree that they really don't give much neck tension.  As mentioned this aids in start pressure and can enhance overall velocity yield of a given load.

My solution to this has been to take the neck mandrel, chuck it up in the lathe (or a drill press) and hit it with crocus cloth, and very carefully reduce it's diameter, testing its effectiveness every now and again by reinstalling in the die, and actually sizing a case or two, until the desired amount of neck tension is obtained.   It is an easy modification to these excellent dies, and can give great rewards in terms of performance.

Just a quick thought on the subject!

God Bless,

Marshall
 
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