.300 BLK case length question

[CQB]

Just ventured into the .300 BLK world.
Cut my first batch of .223 cases down.
Started prepping them based on my hornady handbook (9th edition).
it states, (on page 380 if you're looking), that the max. case length is 1.40" and a trim length of 1.39"
which is how I prepped them.
After some double checking of other sources, I don't see anyone (including SAAMI) that reccommends a case length that exceeds 1.368" with a minimum length of 1.348" for the blackout case.

Hornady's data states it's numbers are for blackout and whisper.
Are the Hornady numbers wrong? Or based on the non standardized whisper case?
If so, why don't they differentiate between the two loads?

So, in short, looking for some INGO insight and wisdom as to what is working for them on .300 BLK

**if it matters, my loads will all be supers with 125 or 150 FMJ's using 'LIL Gun.

 

[kjf48197]

My Hornady book on page 380 says max case length 1.368 and max trim length 1.358. I followed this with no problems, not sure about powder and bullets I am still playing with it.

 

[CQB]

Thanks. Is yours 9th edition? Starting to think my manual is a type-o. Added pic to OP of page from my book

 

[jwh20]

In case you've not seen it, I did a short write-up of 300 BLK here:

https://www.indianagunowners.com/forums/ammunition-reloading/292977-reloading-300-aac-blackout-using-223-5-56-cases.html

But as far as case trim length, I prefer to use SAAMI specification of 1.368 - 0.020 in. So you can trim between 1.348 and 1.368 and be within spec. But the 300 BLK case rests on the shoulder not the neck of the case so it's better to be on the short side (i.e. 1.348 in.) rather than being too long > 1.368" since you might bottom out the neck in the chamber and not fully seat the round.

Note that you'll want to check this length both when first fabricating 300 BLK cases and as you reload them. I have some cases I've reloaded several times and I noticed that the first time I reloaded them they were a bit long but the 2nd time and after they didn't change much if at all.

Just so you know, SAAMI is the standard, not Hornady's book but I can't explain why they would use a different figure than SAAMI.

BTW, here is the SAAMI reference page. This is correct by definition:

http://www.saami.org/pubresources/cc_drawings/Rifle/300 AAC Blackout.pdf

 

[CQB]

Thanks Jwh20. Your write up is actually what had me questioning my manual. Glad I hadn't loaded a buttload of rounds yet.

 

[jwh20]

Thanks Jwh20. Your write up is actually what had me questioning my manual. Glad I hadn't loaded a buttload of rounds yet.

Good to know that at least someone read that!

The 300 BLK is SAAMI specified unlike some other rounds such as .458 SOCOM, which is not currently covered by a published SAAMI spec. So there are some differences in gun manufacturer for that round. Notably Wilson Combat uses a different specification that can cause issues with ammo other than theirs.

 

[sht4brnz]

Look it up on youtube. 300 aac blackout Hornady load manual typo.

 

[kjf48197]

Yup there was a typo and you can google your copy of reloading manual to see if the date is before or after the reprint.