Re: 243ai "trim to" length
The AI cases and their SAAMI counterparts both have the same case OAL.
However, with most AI's when the brass expands in the new AI chamber, the neck will shrink around .0200" because the case is scavenging brass from the walls and neck to form the new sharper neck that is pushed farther forward, and the walls expanding.
For example, Alot of people use .25-06 brass for their .25-06 AI. The SAAMI case length for both is 2.494". When you fire-form regular .25-06 brass in the AI chamber it shrinks to 2.474". It doesn't hurt anything, and the brass will eventually stretch back out after a number of firings.
However, I am very OCD. I reform .270 Win brass because it has a longer neck. I FL size .270 Win brass in a FL .270 Win sizing die, then I run them through my .25-06 AI FL sizing die. Then I trim the brass to 2.514". Then I chamfer and deburr the necks. Then I load them up. That way when I fire them in my .25-06 AI chamber, the brass comes out fully formed, and is a perfect 2.494" in OAL...Plus or minus a couple thousandths.
Like I said, I do mind that way, but that is because I'm extremely OCD about my ammo and when I reload.
And there is absolutely nothing wrong with shooting AI formed .243 brass that is .020" short. It won't hurt a thing.
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Originally Posted by WildRose
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