Quote:
Originally Posted by ronmuse
my ar-15 with a match 1 upper 16.5" suppresed in 300 fireball. I have an adjustable gas block and I'm using wc 820 powder 8.5 to 9 grams with 220 grain bullet. . I'm having ejecting problems.It tries to eject but not quiet, and when it does it doesn't go back far enough to grab the next round. please any ideas. i want to keep it subsonic. thanks ron
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ronmuse,
The powder that you are using has a burn rate that is just a tad too fast. I have read several sources on the internet and the bottom line is that WC820 surplus powder has a burn rate between AA#9 and H110, depending on the lot. Some lots of powder can be as fast as 2400 or AA#7. These should be labeled WC820 (f). So you have three choices.
1.) Increase the powder load slightly until the action cycles correctly. If you have access to a chronograph you can tell if you are still sub-sonic. You might lose a bit of long range accuracy because the bullet goes through a trans-sonic phase during it's flight. But you will have to experiment and see just how your loads work out.
2.) Change to a slightly slower powder like H110 W296 IMR4227 or AA1680.
3.) Play with gas port diameter, bolt/carrier weight, buffer weights, or recoil spring. I like my rifles to run using standard rifle bolts/carriers, spring, and buffer so my lower will work with all of my uppers including my 5.56mm.
The easiest place to start is with the gas rings. Take the bolt/carrier out of the rifle and extend the bolt and stand the bolt up vertical on the bolt face. The rings should be tight enough that the carrier does on slip down on the bolt. If the carrier does not slip down, then the rings are good.
The next step is try running the gun really wet. A lot of people run their AR15's too dry. Lube up the bolt/carrier and upper receiver with a good synthetic motor oil (10-30 or 5-30) or ATF and see if that helps.
The next place to check is the gas port diameter. I do not know what the port diameter is on the Model-1 uppers. But I have read somewhere on the web that you do not want to go more than 0.120-in on the gas port diameter.
Your next option is delving into the buffer and spring realm. The easiest thing to try is cutting a few rings off of the spring. Again I have read that you do not want to cut more than about three rings off of the spring.
The buffer is really a dark art. In a rifle buffer there are weights that slide loosely in the buffer. It is important that these weights can slide back and forth in the buffer because they prevent "bolt bounce" during the cycling of the rifle. You should keep the overall length and number of weights the same. However you can change the material that the weights are made of. For example, if you want to increase the weight of the buffer you can add one or more tungsten weights. Conversely, if you want to lighten the bolt you can replace one of the weights with aluminum.
I hope this helps... If you have any more questions post them
Good Luck
320pf
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