I tried searching, but I didn't see anything. I was wondering what grain of bullet would be the best for an AR with a 1:9 twist rate, and a 20" barrel, chrome lined. I'm not sure it makes a huge difference really, but when I first use my new rifle in a few weeks, I'd like to see what it's REALLY capable of, so I want to try the best weight of bullet.

 

Furthermore, does anyone know where I could get a "dummy round" or something else that I could use to test and make sure the charging handle, and trigger mechanism are working? Since I'm doing this build myself, I want to ensure I'm doing it right.

Off the top of my head (I may be wrong), you're probably best off using XM193 ammo - 55gr. Highest you should go is 62gr IIRC.

 

To test the functionality of your gun - use the following method. Pull the charging handle - you should see it pull the bolt back. Release and the bolt should spring forward. Pull trigger - you should hear a click. Now do it again, but keep the trigger held back. Pull the charging handle again and release. Now release the trigger - you should hear the reset click (Deeper click). Now pull the trigger again and see if you can hear the firing pin click. If you do, you should be good

Off the top of my head (I may be wrong), you're probably best off using XM193 ammo - 55gr. Highest you should go is 62gr IIRC.

 

To test the functionality of your gun - use the following method. Pull the charging handle - you should see it pull the bolt back. Release and the bolt should spring forward. Pull trigger - you should hear a click. Now do it again, but keep the trigger held back. Pull the charging handle again and release. Now release the trigger - you should hear the reset click (Deeper click). Now pull the trigger again and see if you can hear the firing pin click. If you do, you should be good

 

Good. I plan to build it as soon as my LPK comes in, but since I won't be home to build it (as my Poppop has far more tools than I do, and a better workbench/shop setup) I wanted to see how to check it ahead of time, so I could perform all needed function tests.

http://www.shilen.com/calibersAndTwists.html

 

This chart is really handy, it goes by caliber and bullet weight to figure out optimum twist rate

 

-Henry

http://www.shilen.co...sAndTwists.html

 

This chart is really handy, it goes by caliber and bullet weight to figure out optimum twist rate

 

-Henry

 

I didn't see 20" barrel on there for 5.56

Off the top of my head (I may be wrong), you're probably best off using XM193 ammo - 55gr. Highest you should go is 62gr IIRC.

 

1/9 should be good for up to 69gr, but you'll have to test out different ammo to see what rounds your gun likes best

Its .224 center fire, 1 in 9 twist it says bullets up to 70 grain so a 69gn Match king would do well. You will pick up a little velocity over a 16" carbine barrel any way.

I didn't see 20" barrel on there for 5.56

 

That's because for most cases barrel length doesn't make a huge impact in terms of quality of stabilization. For problems, the bullet is either being spun to fast, or too slow. A longer barrel might geta heavier bullet spun fast enough compared to a shorter barrel of the same twist rate, and might get a lighter bullet to reach max spin and shoot like crap, but the sweet spot is going to be approximately the same. That also depends on how fast you are pushing the bullet.

 

a 20" 1:9 sould shoot 50gr to 62gr pretty damn well. 45s can be pushing it but success is not uncommon, same for 68gr. If you are hand loading, you can probably find a load that shoots those fringe weights pretty well.

That's because for most cases barrel length doesn't make a huge impact in terms of quality of stabilization. For problems, the bullet is either being spun to fast, or too slow. A longer barrel might geta heavier bullet spun fast enough compared to a shorter barrel of the same twist rate, and might get a lighter bullet to reach max spin and shoot like crap, but the sweet spot is going to be approximately the same. That also depends on how fast you are pushing the bullet.

 

a 20" 1:9 sould shoot 50gr to 62gr pretty damn well. 45s can be pushing it but success is not uncommon, same for 68gr. If you are hand loading, you can probably find a load that shoots those fringe weights pretty well.

 

You're on the money raz-0. I shoot 69gr in a 1:9 and have to push them kind of fast to stabilize them.