Hello all,

Here are some new test results in Caliber 8X68S:

Case: RWS, Once Fired, FL-Sized and Trimmed
Powder: N560
Primer: Federal 215 match
Bullet: Lapua Naturalis 180 Grain

Charge Weights: 76 grain (top left), 76.5 grain (top right), 77 grain (center), 77.5 grain (bottom left) and 78 grain (bottom right)

It is seen from the target that the 77 grain charge (velocity about 3050 f/s) is optimal. I am very happy to see this but I have two questions:

a) Is it normal to see as much change in POI and group size just by changing 0.5 grain in powder charge? Note that changing the charge has changed both POI and group size not just group size.

b) This rifle has a pressure point underneath the barrel just about two inches before the for-end tip. The barrel is otherwise free-floating. But on close observation I noticed that the barrel gap on the right side is less than the gap on the left side so a dollar bill slips under the barrel with difficulty if inserted from the right side but goes in easily if inserted from the left side of the barrel channel. Can it be that when the barrel was heated, the fore-end somehow touched the barrel and made POI go higher and left as seen in some test groups?

Looking forward to hearing your thougths,

-Omid

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