Need some load advice

[badguybuster]

I have been loading up some subsonic loads for my 300 blackout AR. The bulllets are 247 grain cast lead around an 12 brinell. I started off using 9.5 grains of RL7 and eventually ended up at 10 grains. At 10, I have complete function, very good accuracy, zero recoil, and its pretty quiet (no can on it). The barrel is 10.5". However, I am getting 5-10 unburnt (yellow) kernals of powder left over. Should I be concerned? Suggestions? I also have 4198 and unique if those would be better powders for this task. I know to keep awsy from H110 for subs. Any advice would be appreciated.

[leadman]

AA680 would be a better powder for the 300BO. This has the ideal burn rate and if anything did not burn it is a ball powder so should not cause any problems.
I have a 300 Whisper Contender carbine that I shoot cast, jacketed, subsonic, and sonic. I recently tried Alliant's new 300 MP powder in my Ruger BH Hunter in 41 mag. This powder measures very well and is slower than 296/110 so may work well in the 300 also. I will try it soon. I bought it because it was available at the Sportsman's Warehouse and was less than $20 per pound.
So this might be another powder for you to try if you can find it.
4198 is slower than RL7 and Unique is too fast in a semiauto.

Have you tried a little more RL7 to see what happens?

[Hamish]

At 10, I have complete function, very good accuracy, zero recoil, and its pretty quiet (no can on it).

I think you answered your own question there! Keep it as your primary load data, but nothing wrong with trying a different load. I would think that the 4198 would be a little slow in that short a barrel, but should be worth a shot.

EDIT: doing a little preliminary investigation, (gearing up for a 300 myself), it sounds like you may have trouble getting enough 4198 in the case with heavyweight boolits to cycle. Still sounds like it's worth trying though.

Not on solid ground with PB yet, but from what I have seen, 110, as long as it is not downloaded, is very good with jacketed under 150grains.

[badguybuster]

I only ask cuz I am low on RL7 and noone around here has it

[Hamish]

http://www.300blktalk.com/forum/viewtopic.php?f=141&t=79985

T'were me I would go a snooping,,,,,

[badguybuster]

Well I am having good luck with my 10 grains of RL7 but for some reason unfired rounds are very very hard to get to eject. I think they are hitting the rifling

[badguybuster]

Advice? I ordered a sheridan engineering guage s9 hopefully that will help me isolate what im doing wrong