300 blackout load

[bmiller]

Finally got to shoot my 300 blackout today for the first time. I cast some lee 155 grain bullets and put a gas check on them. I used 15 grains of 296. It did not lead at all, shot accurately. It would not lock the bolt back on the last shot. No pressure signs . Tried one loaded with 16 grains. Still would not lock back the bolt. Once again, no pressure signs. Should I increase the charge?

Thanks for your replies

[John Allen]

Which upper do you have? I have been debating the same thing but was trying to decide between 155 or jumping up to the 220.

[bmiller]

16" carbine length gas system.

[gds]

What is your barrel length and gas system position, pistol or carbine. I would think that load would lock back, regardless. however I have not used 296. Sierras 300 whisper load for 150gr jacketed bullets gives the max for 296 at 17gr.

I have used 16gr of 2400 for that 155 boolit, it is above the max for 150gr jacketed but worked ok in my 16 inch barrel with a carbine position gas system, but is hot in my 9.5 inch pistol gas system upper.

[StratsMan]

BMiller...

There are many differences between uppers/barrels in 300AAC, so the load that cycles my gun may not work for you...

I have a CMMG barrel on mine, carbine length gas system, with a vent hole significantly larger than the same barrel length for 223... If you didn't assemble this upper yourself, you might want to do some checking to see if the vent is enlarged. I've heard that some barrels have (had?) the same size vents as 223 barrels, and those guys had trouble getting anything but full pressure loads to cycle their actions.

[x101airborne]

I dont know if I did it correctly, but I wanted to shoot only subsonic loads out of my 300 AAC, so I worked up a load that shot accurately and then used a set of cutting torch tip cleaners to slowly and carefully enlarge my gas hole in the barrel. It took a long time, but it did eventually function. I just have to be careful to only shoot subsonic loads out of that weapon. I think that a needle drill would work better and faster, but would increase the chance of overdoing it. I then sealed the gas block with pipe thread sealer. This increased the pressure making it all the way to the bolt. That helped a lot, too. One thing that I didn't think of till after I was through, was I think that putting a small bevel on the inside of the gas block would help also. That would help funnel the gasses into the block preventing a partial blockage.

If you do happen to over gas the barrel, it is a simple matter to drill it and make a bushing to control the gasses. Happens more often than you think.

[cutter_spc]

I shoot the same exact load in my rifle (carbine gas and standard CAR buffer), and my bolt locks back 100% (knock on wood, LOL). I would check to see you had good gas port alignment and that your gas key on the BCG is tight, what buffer are you running? If you do decide to open up your gas port, just know it is impossible to over gas a carbine 300 BLK.

[HodakaGA]

Try different mags. It should be holding open without any problems.

[Gunnut 45/454]

Looks like your a little lite on the powder! Try 16 gr as 17 gr is the starting load for 135 gr Jacketed bullets. My load for that bullet is 16.6 gr Lil'Gun and it runs 1950 ish fps out of my 16" carbine with full function an zero pressure signs.

[exile]

Maybe off topic, but in reading posts about the .300 Blackout, I have heard people talk about the Lee 155 grain boolit a lot. Is that the one that is listed as a .312 diameter boolit in the Midway catalogue? Thanks.

exile

[Mike Hughes]

Maybe off topic, but in reading posts about the .300 Blackout, I have heard people talk about the Lee 155 grain boolit a lot. Is that the one that is listed as a .312 diameter boolit in the Midway catalogue? Thanks.

exile

Yes, thats the one. I was going to buy an extra , but everybody is sold out. There might be one on ebay at an inflated price

[Gunnut 45/454]

bmiller
I'd try 16.5 gr next! Or switch to Lil'Gun 16 gr works prefectly in my 16" carbine. That Lee 155 is the perfect bullet for the 300 Blk IMO!

[Jailer]

First check your mags to eliminate that possibilty and then check your gas port alignment. I started showing some pressure signs at 16.5 gr H110 and at 17 gr ended up with this.

http://i19.photobucket.com/albums/b180/Jailer/presssure.jpg

[blikseme300]

BMiller...

There are many differences between uppers/barrels in 300AAC, so the load that cycles my gun may not work for you...

I have a CMMG barrel on mine, carbine length gas system, with a vent hole significantly larger than the same barrel length for 223... If you didn't assemble this upper yourself, you might want to do some checking to see if the vent is enlarged. I've heard that some barrels have (had?) the same size vents as 223 barrels, and those guys had trouble getting anything but full pressure loads to cycle their actions.

The differences are real. I have 2 300blk 16" uppers with barrels from different manufacturers and the faster powders like Lil Gun only locks the bolt open for one of these. I had less than stellar accuracy with the Lee C312-155-C2 when using faster powders like Lil Gun and H110. After much experimenting I now use 16gn of Reloder 7 behind this boolit and accuracy is good and the bolt locks open with both uppers. My conclusion is that it is not only how hard you push the boolit but the duration of the push that determines proper functioning. The 2 barrels are: Sota Arms HBAR 16" SS with carbine length gas port and AR-Stoner LW 16" SS with carbine length gas port.

[Liberty'sSon]

I have a 300 blk barrel that came from Sportsmanship Guide 16 in carbine gas port. Had to enlarge the gas port to get function on factory Remington 115grain j words.

[Gunnut 45/454]

bmiller
You could go to a lighter buffer that might get it done, also lube ,lube lube. Run your BCG wet might help as well.