.300 Whisper Ar 15

[gds]

I just got my .300 Whisper Barrel for My AR. I love it. But I am having difficulty with a subsonic load using the Lee 200 gr boolit. I can get a Subsonic load, but not yet got one to Cycle the action

Does anyone have any experience getting one to cycle subsonic with 200 gr cast?

The barrel
16.25"
1 in 10 twist
Carbine gas Position
Gas port size .125
Adjustable JP gas block

I have

Red Dot
Blue Dot
2400
1680
Rx 7

Super sonic load
125 gr Sierra JSP
20.5 gr 1680
2000 fps
Works great and good groupings so far.

[BerdanIII]

Have you tried the Silencer Talk website? They have a fair amount of subsonic data in the reloading forum.

[redneckdan]

It is hard to get a subsonic load to cycle the action with a carbine gas port position. I kept working down with powder burn rates until I got to the point where unburned powder was getting tossed out the barrel and never got enough pressure at the port to cycle the action. If you plan to shoot a lot of subsonics I would convert to a pistol position port. If you are dead set on keeping the carbine position try to find the lightest bolt carrier spring and buffer you can find. And use the slowest powder possible.


PS- be VERY wary of any data you find on the internet. Even SSKs stuff. I found several loads that were pushing the limits even when I was 2.0gr below the published maximum.

[burr7870]

I use AA1680 @ about 9.5 grains behind the lee 200 gr GC bullet for subsonic. H110 cycles fine with supersonic loads. 2400 I am still working on loads. My M1 sales upper is standard with the carbine position gas port. I do not have an adjustable gas block.

Good Luck

[gds]

I use AA1680 @ about 9.5 grains behind the lee 200 gr GC bullet for subsonic. H110 cycles fine with supersonic loads. 2400 I am still working on loads. My M1 sales upper is standard with the carbine position gas port. I do not have an adjustable gas block.

Good Luck

Does the 1680 Load Cycle the action?

[burr7870]

Yes it AA1680 cycles the action. The cases drop comparable to the supersonic H110 loads. The other issue you may have with a new upper ithe bolt needs to be "broke in". It may take 100 rounds of supersonic to get the upper ready. I tried 2400 for subsonics it was not even close to cycling the action (even after going supersonic it would only cycle with near maximum charges). I think you'll like the AA1680.

[gds]

The bolt, carrier and upper are all well used parts. The 1680 was great for my super sonic loading, So I am going to do some more playing around with it later this afternoon if I get off work in time. I had the same problem with the 2400. Which stinks because I have a lot of it. What is your COL for the subsonic load?

[burr7870]

I can't remember the exact measurement but if you keep the gas check in the neck it is near max oal to fit into the magazine. I had planned on using the 2400 as well. I am working up a load using the 2400 & a lighter bullet (supersonic).

[gds]

Thanks Burr7870 that helped me get started. I had to bump it up to 10.1 gr before I could get reliable cycling. But I could not get the bolt to lock back on the last round. I was right at the sound barrier.

I did get to try some 2400 on some other cast bullets.

155 gr lee 17g @ 2000 fps
120 gr pointed 18.3g @ 2250fps

[burr7870]

Try lubing the bolt carrier lightly. My AR cycled at about 9gr AA1680. Little finicky but once you get it figured out it is a load of fun. My son loves the mild recoil & lack of muzzle blast. It looks like you crono'd your loads I would be intrersted in the lower speed load velocities.

Thanks

[gds]

Yeah I love the chronograph. I completely cleaned the rifle and that is how I got it to work. I was getting cycling at 9.3 grains but it was inconsistent, on feeding the next round. When I went up to the next cavity in my lee powder disk, I got good function, but not lock back on the last round. They are averaging 1025 fps, which is a little faster than I want, but it works. I may get a lighter buffer and see if that helps any.