Tolerances

[DevilDawg]

When trimming cases what tolerance do you hold? Example: Book calls for case to be trimmed to 2.25". Do you work at it until you have that dimention on ther money, or do you allow .002, 005, 010, over/under.

 

[Blaine]

I don't trim until the case length exceeds SAAMI spec's. Then I trim to the "trim to" length (usually .010" less than max) and trim all cases equal. I try to not go under the "trim to" length, but if all the cases are equal, I don't mind being .002-.004" long. I don't think being a little short hurts anything as long as they are all trimmed the same. The only thing is on some case necks, like the 300 Win Mag, for example, you need all the neck you can get. The keys are 1) Don't exceed SAAMI max length, and 2) Keep all cases in the same batch equal.

Blaine

 

[REDGREEN]

I trim .005 less than chamber length. The shorter that you trim them, the more your bullet is deformed on acceleration leaving the case. If you are neck sizing there shouldn't be too much stretching and trimming will be needed again after 5 or 6 firings. Check your chamber length. You may be able to get away with even less of a trim job.

 

[longwinters]

Ahhh, but to measure the rifle chamber length you have to have some type of device ie . . . stoney point etc right?

Long

 

[rick smith]

The Stoney Point tools do not measure chamber length. Sinclair sells inserts that fit in the neck of a case that is used to measure chamber length.Rick.