220 Load

[S.Mortium]

What powder and grains will get 220 to highest supersonic speed out of 16 " BBL?

[Jargonhead]

http://www.300whisper.com/supersonic.html

I would reduce those loads to start by at least 10%

Rob

[randyrucker]

What powder and grains will get 220 to highest supersonic speed out of 16 " BBL?

A1680 seems to work best for the heavy projectiles. Getting a 220gr bullet supersonic with the Blk Out is just barely achievable. Here are some numbers for it:

[Jargonhead]

I wouldn't call 1492 fps barely achievable. Not sure of the OP's question but that's the number.

15.6

AA No. 1680

1492

11 AR-15



Rob

[randyrucker]

I wouldn't call 1492 fps barely achievable. Not sure of the OP's question but that's the number.

15.6

AA No. 1680

1492

11 AR-15



Rob

I'm not trying to quibble about numbers, but your data is for the Whisper using a 16.5 inch barrel. While I would experiment with them if I had no other reference, I would rather use the published data from Accurate. 15.6 grains of A1680 is well above the Accurate published max for a 220 grain projectile. It would be interesting to see if one could get to that load without a major malfunction though.

[Dochartaigh]

Here's my FPS numbers (left column) using A1680 and Sierra 220's in a 9" barrel. Granted people say your FPS will raise 10-20 FPS when using a suppressor (I just got my suppressor this week so I haven't chrono'd yet to verify that), I would say this is a good starting point for your 16" barrel...and if it's cold out might even bump the FPS to the threshold of sub/supersonic (speed of sound at 20 degrees is 1073 FPS...and it was near that out today).



And here's the suggested subsonic load straight from AAC:

• R-P 300 AAC BLACKOUT brass
• Remington 7.5 primers
• 11.2 grains of A1680 powder (Adjust powder charge down as needed. Factory ammo is 1010 fps for 16" barrel)
• Case length is 1.368 +0.000 -0.020
• Sierra 220 MK loaded to 2.120 OAL (this length is optimal for reliable feeding from USGI magazines)
• Chamber pressure 21,100 psi.

[20X11]

I ran 10.5 gr H110 behind a couple of SMK220s at OAL of 2.08 with rem 71/2 primers for 1350 fps. 16 inch carbine gas cycled fine, but I wasn't interested in developing the load any further.

[supersniper]

when trying out powders for sub loads with 230 Lee cast bullet - 10.0gr of 2400 gave me around 1330fps