Accurate's dimensions
 

Yeah, Accurate Arms shows a case length of 1.36" maximum but also a neck only length of .306" and a base to shoulder length of 1.076". Do the math; that's not possible.

It seems that nobody knows what the actual dimensions are. Strange.

The best thing to do would be to trim back a case until you know what all your chambers are. Start long and go in increments til the brass will let the bolt close. They might only have a trim length of 1.355" listed because 1.360" is about as much length as you're going to get with a 221 case. I remember reading somewhere that the proper way to make 300 whisper brass is with 223 cases.
My 30-221 reamer cuts just past the 1.400" mark. If you listen to the Bench Rest guys a longer neck is better for accuracy as it keeps the bullet aligned longer or something like that. When I start making another batch of brass I'm going to use 223 this time to find out what my chambers are first then find a good length to trim to.
So the correct OAL is what will fit in your chambers.

Nick

I spoke to JD Jones not too long ago and one of the questions that came up was case length.....the 221 fireball brass I have is 1.401 after it is necked up it is 1.405.....my SSK 300 whisper guns work fine with this length...

Wow, last's way longer than the batch of 221 I bought.
Some people get lucky I guess.

Nick

the 221 brass I have is older Remington.....if you need additional neck length for your 221 fireball you can always re-form 222 remington, I like the Norma for doing this, it is beautiful brass and the neck wall ends up a little heavier and it can be turned to the desired length and thickness....I have some of the Norma that I have done this with over 10 reloads....the Norma is more expensive up front but lasts much longer.....also works great for making 300 Whisper brass....

The best thing to do is get the Sinclair tool and measure your own chamber length. Mine is 1.409 I trim my brass to 1.399 and consider 1.404 to be MAX case length. I suspect the neck varies from one barrel to another. Mine shows .336 with a Cerrosafe casting.

geetting my upper for 300 whisper in a week. need help with whatever i need to get started reloading. would like to shot sub ammo.

new upper is here
 

that was fast order two days ago and its here.Now i need to get things started.new a sub load with 200 to 240 gr. bullet.Hep guys.

SI defense barrels are 1.41" so trim length is 1.40". I also have to neck turn .223 cases quite a bit to make them chamber.

man this is complex. what case length should i use?
i'm about to start converting my .222 and .223 cases to 300/221.
the gunsmith hasn't finished with my barrel.

do i have to wait for the barrel and then try to measure what the my overall case length is? i bought the reamer based on some suggestions from this forum, but i don't remember where from.

lot of misleading info on the web
1.4" = 35.56mm according to http://www.ar15barrels.com/forming.shtml

1.35" = 34.29mm according to http://en.wikipedia.org/wiki/.300_Whisper

anyway. i trimmed my cases to 1.4. i'm not going to reload anything until i can try to fit it into the barrel