Subsonic

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Subsonic

Postby BD1 » Sun Jun 14, 2009 8:12 pm

I tried five Lyman 457193s yesterday over 11 grains of Unique just to see what was possible to stabilize subsonically. These weigh 413 grains in my current alloy. Actually they didn't shoot that bad. I got a 3" group at 100 yards, (1/2" vertical dispersion, 3" horizontal dispersion). Considering they were the last five shots out of 60, a lot of that horizontal dispersion was probably me as I wasn't really working at it. I just wanted to see if they'd make round holes, and they did. I lubed them by hand, as I don't have a .458 lube sizer die, and then sized them to .452. They hold a lot of lube, and they were smoky, but they shot pretty well. Next time I'll try some out of a clean barrel when I'm really paying attention. AV was 1030 fps, ES was 29.24 and he SD was only 11.18. High Velocity was 1040 fps, so this could make a reliable subsonic load. Might be it could even be bumped up a little. I did need to hand cycle the action, which is not a bad thing if your intention is to be quiet.

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Re: Subsonic

Postby Siringo » Sun Jun 14, 2009 8:28 pm

Interesting! I had shot some 405 grainers, but I used 5744. I did have low velocities, but lots of unburned powder - typical of 5744. Not a good thing in an auto. How did they eject -- as compared to the factory rounds?
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Re: Subsonic

Postby BD1 » Mon Jun 15, 2009 9:15 am

I had to eject them by hand, as the light load of Unique would not cycle the action.
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Re: Subsonic

Postby wildcatter » Mon Jun 15, 2009 1:38 pm

Years ago in the 45 pro days, I did a military contract for some 500gr 458's resized down to 452 @ full pressures I still didn't get them to function on semi auto, the Military lost interest, and soon I did too, so I never fully spec them out. My guess is with some further work a serious Hush-Puppy 500gr load would be very possible.
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Re: Subsonic

Postby BD1 » Mon Jun 15, 2009 1:47 pm

The bigger the bore, the harder it is to keep it quiet. Even a .44 airgun makes some real noise. To get the action to function with cat sneeze loads might require moving the gas port closer to the chamber. The "James Bond" set up might be an 18" barrel with 3 gas ports and some method of selecting the one required for the particular application.
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Re: Subsonic

Postby Colohunter » Tue Dec 01, 2009 1:51 am

Has anybody else tried the subsonic loads anymore? I shoot a 300 Whisper and when I get my 450 in the mail next week I wouldn't mind trying he 450 subsonic. I know there has been some experimenting with really heavy bullets in the 458 crowd. I know with the Whisper I have to change powders to get performance out of the subsonic loads.
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Re: Subsonic

Postby BD1 » Tue Dec 01, 2009 7:24 am

My loading gear is still in boxes in the garage from the move back to SC. I'm hoping to get that room up and running in the next week or so. Does anyone have a gas checked 400+ grain design to try?
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Re: Subsonic

Postby Siringo » Tue Dec 01, 2009 9:12 am

I didn't keep my records, but when I shot the 405's w/5744, I did get the action to cycle. However, I had significant ejector swipes on the cartridge case base. That coupled with lots of unburned powder prompted me to abandon the effort. My goal was to duplicate a 45-70 load with a lead bullet at 1300 fps (so I could shoot along with some buddies with their black powder rifles at an informal competition -- a spoof). The marks at the base of the case are most likely caused by the action opening before the pressure has dropped (slow bullet speed) rather than by excessive pressure alone. I was using a buffer that weighed only 2.8 oz and I should have been using a heavier one. Looking at 458 socom and 50 beowulf chatter -- they are using heavy buffers in the carbine stocks. One company -- http://www.heavybuffers.com, makes buffers that weigh 6.5 oz and 8 oz. These are expensive. Another alternative is to use weights attached to the bolt carrier. Go to http://www.davidtubb.com. Only drawback that I can see with the carrier weight system is both pins have to be removed from the upper/lower to dissassemble the action. It will not tip open.
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Re: Subsonic

Postby Colohunter » Tue Dec 01, 2009 1:43 pm

That's good to know about the buffer weights Siringo. For subsonic in other rounds usually you try to keep fps at about 1050fps. Has anyone experimented with different powders or bullets to try and maintain that speed and still cycle the action? I was looking through Midway and noticed that they have several .458 bullets in the 450-500gr range. A lot of them are pretty expensive, but there might be a couple worth trying. I know the hardest thing would be to get the action to still cycle reliably. With the 300 Whisper most people use a pistol gas system, but with the right powder selectino you can use a carbine system and still cycle the action.
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Re: Subsonic

Postby wildcatter » Tue Dec 01, 2009 4:39 pm

Resize the .458 heavy weights (500-700gr) to .452 and go for it. I've had many heavys' cycle the action at sub-sonic velocities..
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