02-15-2014, 03:55 AM
woohoo Wrote:further-Our earlier posts suggest that we agree that we still need to see a bonafide SAAMI chamber compared to a "scraped" throat chamber.
The minimum 264LBC reamer has a .042" freebore, mid spec .080 and the largest .118".
The minimum Grendel SAAMI chamber has a .023" freebore. If the reamer is .001" larger in diameter than the minimum size the freebore is .137". If the reamer is the largest allowable spec in the Grendel the freebore is .251" That'll leave a ring.
Edited- I was off on the calculations, that's what I get for doing it on paper instead of a calculator. each .001" change in dia lengthens the freebore .114" using .5 degree as the angle
The increase in freebore length can be no more than the .015 inches called out in the length tolerance by the SAAMI drawing. The .2644" dimension is allowed to float a bit because the drawing calls this out as a reference dimension.
The .5 degrees references the line you see on the drawing. If it were the included, or total, angle the call-out would have been different. This tells us that we need to account for the other side of the neck which also has a 0.5 degree taper, giving an included angle of 1 degree.
Applying this to a 1 mil diameter change results in a .057" change in where the ogive would touch the freebore for each change of nominal diameter of .001 inch.
These numbers also happen to get us closer to the reference dimension of .2644" at the start of the freebore.