So I have a ruger 77 in 7x57 that has been beded and is an honest 1/2 inch gun with Hornady Custom ammo 139 grn Interlok and shoots about an 7/8 with Hornday Light Mag 139 SSTs.

I have bought 3 boxes of Custom and a box of Lt Mag. Brass is Brass right no need to segregate.

Wrong. I start reloading with 154 grainers and my groups are doing wierd things...some running 3/4 or so...others running 1 3/4 okay maybe its windy that day maybe I am flinching from shooting a my hard kicking other rifle.

Go to the range again...WOW 2/3 inch groups pretty consistent...oops a couple 1.5 inch groups.

I read this article on weighing brass like the BR guys do. Guess what... I have 20 cases that weigh right around 175 grains and 60 cases that are right at 192 grains. Thats a difference of just under 10% or just over 10% depending on which weigh you do the math.

Is this news or was it common knowledge that Hornday light mag ammo uses thinner brass to help increase voulme and reduce pressures. BTW this is my speculation. I can't state for certain which cases were from which boxes but awfully coincidental.

Comments?

[ 05-27-2002, 22:51: Message edited by: Mike Dettorre ]

need some comments here...

Mike,
all I can say is that I have very recently loaded some ammo for a good friend of mine using once fired hornady light magnum brass, and case capacity was almost 3 grains of MRP larger than the RWS cases I had used to develop his load!
montero

If the groups randomly got bigger it may not be the cause of your problem. If the bigger groups were composed of two smaller groups then your point of impact is changing between the two ranges of case weights. In other words, two 1/2 inch groups about 1 inch apart would make one group measuring 1.5 inches.

Reed