Thread: .300 Blackout help

Hi Guys,
What subsonic loads are you using with my 151HP projectiles,
My Chronograph is on the blink I can't get a velocity reading
So far I have tried 3.5 grs of Trail Boss and 2.5 grs of 700X
both are quite accurate and quiet.

Off the top of my head, I used 6.2 grains under 125gr jacketed bullets for about 1050. 16.5" barrel.

I know plain lead is easier to drive down the barrel, but I'd have thought you'd need a bit more than 3.5gr to get up close to 1000.

Not that it helps, but I run 13.2g of n110 in my 338br with 300gr and mY magnetospeed needs to be turned to highest sensitivity to read the apeeds.

Out of interest what it the over all length with your 151gr HP projectile loaded? Trying to figure out if I can crimp on the cannelure & still fit in my short magazine. Another random question do your cast 151gr HP shoot better a specific distance of the lands?

Originally Posted by LJP

Out of interest what it the over all length with your 151gr HP projectile loaded? Trying to figure out if I can crimp on the cannelure & still fit in my short magazine. Another random question do your cast 151gr HP shoot better a specific distance of the lands?

Just use the crimp groove the bullet is designed for a standard .308 throat the 300BLk is the same, Cast bullet don't like being jambe into the lands
just a light touch I find it easier to crimp in the groove they don't mind a jump
They will fit your magazine My blackout is built on a .222 and mag length is 2.130" no problem with 147 gr FMJ's crimped in the cannelure .223 OAL is 2.260".

I didnt get down that low in the x39mm tuning by ear...4grns was as low as I dared go..stupidly small amount....

The 300 BLK case is very small I worked up from 2.5 Grs 700X to 3.1 grs at 50M 5 shot groups were going under 1"
sound was ok without ear defenders
Got too busy and the weather turned to shit will have another crack at it when the weather improves and the orders stop
coming in.

Originally Posted by shooternz

The 300 BLK case is very small I worked up from 2.5 Grs 700X to 3.1 grs at 50M 5 shot groups were going under 1"
sound was ok without ear defenders
Got too busy and the weather turned to shit will have another crack at it when the weather improves and the orders stop
coming in.

@shooternz, I read some very interesting trial results for a range of different powders vs group sizes for subs. 700x produced the smallest group out of an extensive range of powders at one charge weight, but then produced the worst groups of all powders if the charge went up or down a 10th of a grain, 1/2" turns into 12" group. I would not use it myself because it may cause baldness.

Originally Posted by Moa Hunter

@shooternz, I read some very interesting trial results for a range of different powders vs group sizes for subs. 700x produced the smallest group out of an extensive range of powders at one charge weight, but then produced the worst groups of all powders if the charge went up or down a 10th of a grain, 1/2" turns into 12" group. I would not use it myself because it may cause baldness.

Too late on the baldness, I have quite a lot of 700X and it is easy to find, the few loads I have tried so far are accurate enough to use in place of a .22RF that I don't have
which was why I got the Blackout put together, Just need to get a bullet mould that doesn't need Gas Checks and will save $0.10 a shot,
I see a new Blackout round has been released the 8.6 great for those with an AR10 lying around.