10-04-2013, 11:17 PM
LRRPF52 Wrote:The .473" diameter is for the .30-06 and .308 case head families, not the Grendel. The Grendel uses a .441" case head diameter. The bolt head is a little wider. I just measured one at .447"
The Grendel bolt is a complete re-design, since you need to account for other things than case head diameter. Extractor geometry being a key consideration.
My experience has been similar to this. I have used a .473 bolt face for my initial load work up in the .20 Grendel in a Savage Model 16. The main challenge is that the extractor does not always grab the rim so the old cleaning rod gets exercised.
So, yes, pay attention to the extractor details.
Note the the 7 mil tolerance between the rim and the sides of the bolt face. Further, the base of the cartridge is not entirely supported by the chamber wall, so if the rim expands to meet the sides of the bolt face, brass will already be seriously flowing in other places.