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Posted: 1/3/2010 6:46:45 AM EDT
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Ok a lot of people say their worthless and that it's not possible .... beyond any of that it has been done, and I would just like to try and duplicate it. There a ton of people out there that would like to shoot their .223 AR15 with subsonic loads that cycle the action for fun/practice if nothing else. Other than small (very small) animals and teaching purposes they do not offer a lot to the shooter as far as usefulness, but I know plenty of people that would love to shoot their AR15 with a "quite" round without paying for a conversion kit. Like I said ... its more to just do what I know is possible of being done. Since anything over a 77g bullet is not easily found that would fit in a magazine (I couldnt find ANY); I decided to use the Hornady 75g BTHP Match bullet. They are relatively inexpensive and easy to find in large quantities. I used (4) different powders with (4) different loads each with some interesting results. First I started with IMR 4064 .... This powder is used in the heavier 223 bullets, and the large extruded granules would help fill up the case without the need of a filler. I used 10g to start with ... it would not cycle the action and was already above subsonic speeds. onto the next.... Second I used H50BMG.... This powder is extruded like 4064 and burns very clean. I built up (4) rounds using 14g of powder. This would bring the action about 1/2 back but failed to eject the round ... one round actually ejected the brass but did not strip the next round from the mag. There was very little unburnt powder, but oddly the speed on these were fast for such a slow burning powder. Third I used US869.... This ia a ball powder and I didn't have much hope for this one since ball powders are notorious for being difficult to light. My concerns were well founded .... though the 12g powder charge ejected the round and began to feed the second ... it failed to chamber because of the amount of unburnt powder. Not a good candidate.... Finally I used Retumbo... This is a heavy extruded powder too ... it is extremely clean burning as well and is used in some of the biggest magnums out there. With the four different combinations that I used I found that 16g of Retumbo actually did a very good job of cycling the action and feeding the second round. Unfortunately after 2-3 rounds there would be enough grains of unburnt powder to keep the next round from chambering. In conclusion; I don't think it would be very difficult to work up a good sub load that cycled the AR's action reliably. It would definately help if there was a 90g bullet out there that was readily available and would still fit in the magazine of the rifle. If nothing else it was fun to look at the results and see the challenges ahead ... none of these loads showed any signs of pressure; but nearly all of them left the spent case blackened from the neck down to the mid point of the body. Sarg These are not recommended loads from ANY manufacturer and I DO NOT recommend trying ANY of them in ANY combination. This was just for informational purposes ONLY! |
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I recommend you read up on Secondary Explosive Effect before you expand your experiments.
I'm one person that agrees with the notion that reduced loads are useful, for exactly the same reasons as men such as Phil Sharpe did. Even in gas operated firearms that are reduced to single shooters, there is a place, it's up to every individual to decide how and what he will shoot. I spent a fair bit of time last week working on light recoiling loads for killing coyotes with the .30-06 last week. But there are safe reduced loads, and unsafe reduced loads. Scrimping on gunpowder to save money is okay, but it needs to be done with smarts. An AR action requires about 14 kpsi at the port to operate the bolt; check the info in the Reloading Resources for the exact figure used for US military ammunition. So, a load of Unique that produces 5 kpsi peak pressure ain't gonna operate the action, no matter how badly someone wants it to. |
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