300Whisper trim to length 1.355 not 1.400!
 

About once a month, someone is trimming down brass for their 300 whisper to 1.4". It's a pretty common mistake since that is the length of the .221 fireball; but not the 300 whisper. The real trim to length for the 300 whisper is 1.355".
Don't feel too bad. Even the Hornady book got it wrong.
The new Sierra book got it right.

How about a sticky for the trim to length before someone gets hurt trying to chamber a case that is too long in a 300 whisper chamber?
Gos.

The funny thing is I had a brain fart and trimmed all my brass to 1.450", and loaded them up. They fed and functioned perfectly in my upper. Hell, I even loaded them another 3 times without trimming them again and they still worked perfectly. I must have a big ass chamber!

I've loaded for some guns that did accept the 1.4 with no problems, but I have seen others that did not. I'm just wanting to see this thing set to a standard length.
It would be interesting to see with a casting what your chamber length really is. What brand is your barrel?
Gos.

I have no idea. The seller told me it was an Armalite SS barrel. I never heard that Armalite ever made any Whisper barrels, but that's what the guy told me.

What we need is some technical Specs and FAQ....

Here is a related thread from the past:

http://www.quarterbore.net/forums/showthread.php?t=147

case dimensions
 

ammoguide.com shows the following dimensions for the .300 Whisper:

Case length: 1.40"
Neck id.: .308"
Neck od.: .330"
Neck length: .228"
Shoulder angle: 11 degrees
Body dia. @ shoulder: .369"
Shoulder to base: 1.070"
Body dia. above rim: .375"
Rim dia.: .375"

Which measurements are inaccurate, other than case length?

I'm looking at my hornady reloading manual, it shows case length of 1.4" but it has a 1.355 case trim length.

Case length: 1.40"
Neck od.: .335"
Shoulder angle: 23 degrees
Body dia. @ shoulder: .361"
Shoulder to base: 1.070" - if you do the math its 1.071
1.101 ot the front of the shoulder
Body dia. above rim: .376"
Rim dia.: .378"

Thats from the hornady book by copying and pasting yours and changing the numbers, I deleted the numbers that weren't there.


Jon

Case Length
 

Hmmmm ... I'm holding a page I printed off the Internet (I think it's from Accurate's website, as it only lists their powders) showing the 300 whisper (note: not named as 300 Fireball, and the description quotes JD Jones) and all of it's dimensions. The dimension from the rear surface of the case to the end of the neck is lsted as 1.360 inches, with an overall loaded round length of 2.245 inches.

Miker

I have cut my chamber with a 30/221 chamber from ptg, and I need to trim my brass at 1.350 otherwise it does not chamber.

Nic

The Sierra manual lists 1.365 as the case length and calls it 300-221 but also mentions Fireball and Whisper as alternate names. :eek: I'll say this. After starting the process of making my own brass, buying suddenly doesn't seem so expensive. :wink:

Edited to add My Sierra manual shows 1.360 as the trim length.

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

300 AAC BLACKOUT is 1.348 to 1.368.

Trim to 1.360.

is the blackout the same case?

everybody agree that i should trim to 1.360"?

pinched necks and blown primers
 

I say 1.355 is a good length and I will be trimming to that measurement from now on.
I wish I had found this thread before making brass. I had two pieces of brass at 1.395 and 28 more pieces at 1.375 inch. The 1.375 brass shot ok, but the 1.395 blew the primers. (Savage bolt gun, and could not tell any difference upon firing. The primers fell out of the pockets upon ejection) Looking at the brass you can see how it pinched the bullet at the neck and made the pressures spike. I measured the blown cases from the base to where I can see it begin to taper. On my gun it looks like the chamber is somewhere around 1.360 -1.365 long.

I am making all my brass 1.355 inches long from now on.

1.358 is center of the 300 BLK range.