300 BLK - Midweight Loads?

[Greg]

.300 Whisper & Cast

I have some loads that I worked up for my 10" Contender that ya’ll might look at


R-P - Fireball brass necked up
R-P - 7½ primers

Lyman 311679 cast 95-3-2 water quenched
sized .311 / Hornady GC - 208 grains

14.8 grains AA1680;
I had gone up higher but this was the sweet spot for accuracy,
round primers and easy extraction.

1530 fps in a 10" Contender

~~~~~~~~~~~~~
R-P - Fireball brass necked up
W-W - SPM primers

RCBS 30-150 FN cast 50:50 WW & lead
sized .311 / Hornady GC - 160 grains

18.4 grains AA1680;
I had gone up higher but this was the sweet spot for accuracy,
round primers and easy extraction.

2080 fps in a 10" Contender

the RCBS cast at .309 it was borrowed, so it went back…I had Dan at Mountain Moulds cut me a copy to drop at .311/.301
I still shoot this boolit / load.

[HodakaGA]

Thanks for the load data. Keep it coming.

I have one or 2 full cans of WW680. Of course I'd work up loads, but can't it be substituted for AA1680?

[StratsMan]

My burn rate chart shows XMP5744 much closer to WW680... both slower than 1680, but the burn rate chart doesn't tell you everything!!! I have used 5744 in mid-range 300 BLK loads... They cycle my AR just fine... Don't have a chrony, so not sure about velocities...

Using a Lee C312-155 mold (for 7.62x39) and sizing at .311, 17.5grains of 5744 cycled smoothly and recoil was mild... IF I had any WW680, and was gonna load with this bullet, I'd drop that down a bit, say to 16.0 grains, and start working up from there.

[Greg]

any internet load should be double checked against a loading manual

then start 10 % below and work up slowly

[StratsMan]

any internet load should be double checked against a loading manual then start 10 % below and work up slowly

Greg, that's a good rule to follow if you can find a recipe from a loading manual... The SAAMI spec for 300 BLK is new enough that not everyone has published data yet... I've not done an exhaustive search, but I wasn't able to find loading data for 300 Blackout at the Accurate website...

If anyone knows where it's published, please share....

[donnis]

Exactly what I was thinking. Hodgdon has some data and I'd also trust the recent Guns and Ammo article. Haven't see much other "official" data.

[Johnk454]

Just getting started myself, so not a lot of info to share. Loaded these Lyman 311041s today over a starting load of 297. Hope to find a good spot around 1800fps, but we will see.

[Greg]

Hornady and Sierra both have published loading data for the .300 Whisper ~ email them

American Rifleman ~ May 2008 ~ .300 Whisper

Hodgdon has 300 AAC Blackout data ~ on line

[Gunnut 45/454]

My main plinking /target load will be the Lee 150 gr GC over 16.5 gr of IMR4227. Chronied out of my 16" CMMG I'm getting 1829 fps!

[Greg]

a short American Rifleman article on the .300 Whisper is here...

http://www.americanrifleman.org/m-ar...id=1368&cid=31

[sparky45]

Just getting started myself, so not a lot of info to share. Loaded these Lyman 311041s today over a starting load of 297. Hope to find a good spot around 1800fps, but we will see.

What Dies are you using John? BTW, VERY nice looking rounds.
Sparky

[27judge]

im thinking of a 300 blackout upper from cmmg ,what can one expect in accuracy 25 to 50 yards with cast bullets. i have a lyman 311291 and a rcbs 180sp both with gas checks and a pile of 1680 and 2015 would like to hear any input. this would be a play/plinker rifle as i have a upper from white oak in 223 and another from dtech in 6x45 for any long range shooting tks for your time ken

[sparky45]

I was notified by Midwayusa that my CMMG 300 blackout upper was shipped last Friday, can't hardly wait. I have the Lyman 311291 to use and some Sierra 110gr BTHP's to try as well. I have a number of different pwds. to try but will stay with H110 and maybe some Trailboss. Any load data for cast would be appreciated.

[StratsMan]

I have a 300 BLK CMMG barrel from Midway, that I assembled the way I want it... when I load up my 235 grain GC boolit (Accurate Arms #31-235B) and get it up to high sub-sonic velocity (appx 1000 - 1100 fps), with AA1680, my 5-shot group dropped down significantly... covered with a quarter.... (25 yds)

I'm confident the barrel and load are more capable than I....

Of course, YMMV.....

[leadman]

I had both a 1 in 10 and a 1 in 8 twist barrels for my Contender. The 1/10 was a 10" and the 1/8 is 18". The 10" barrels would match the velocities for the 18" with the same pressure signs.
So pay attention to what twist the load was worked up in.
T/C barrels are 1 in 10 twist.