Put my 300/221 AR15 together

[ReAX222]

I finally got my RRA match lower put on my Model 1 upper. I built 400 cases out of 5.56 cases, cut, formed, ect. I took the rifle out to the range on Sunday and it is short stroking. I am new to the AR platform, so bear with a little please.

It is short stroking, it extracted every case after firing, but the bolt closed on an empty chamber. At the end of my 5 round magazine, it did not lock open but closed on an empty chamber.

I cleaned it up today, the gas tube and key seem free. I couldn't tell if the pipe cleaner went in to the barrel, but it did pass through the key. I moved the gas block to check the hole, it's right at 0.120". There is a band of sliver where either the barrel didn't get coated or the coating has warn off. That band is just slightly wider than the hole in the barrel leading me to believe that the block's hole is atleast 0.120".

So do I need to cut the recoil spring or should I invest in an adjustable gas block? Is there anything else I can do to correct the short stroking?

[320pf]

What powder, bullet weight and load were you shooting? This information would be helpful in figuring things out.

I would shoot at least 200 rounds through the gun before I would get too excited about the short stroking. Also AR's like to run wet particularly when they are new and tight. My favorite oil is either ATF or Moble-1 synthetic 5-20 or 5-30 weight.

320pf

[Ron458]

Like 320pf said, what loads?

My favorite oil is either ATF or Moble-1 synthetic 5-20 or 5-30 weight.

Great idea 320pf

[ReAX222]

Going back to my notes, I built 10 rounds (I only shot 5 of them) 220gr Sierra Match kings, 10.0grs of 2400. OAL 2.260" built in February and it was cold (probably in the 50-60 degree range.) When I was shooting it was roughly mid 90s and very humid.

The upper was used and should have just over 100 rounds through it. I did drop some rem oil in the lower and I used my FP10 grease on the upper.

[Flewis]

You might check your gas block and make sure the gas tube is not misaligned in the block. I had that happen with an upper I recently bought. I corrected that and it cycles perfectly now. You also want to measure and align the port in the gas block perfectly with the port in the barrel. In my experience it takes all the gas you can get in order for heavy sub-sonics to cycle in a carbine length system.

Model1Sales also sells a lightened bolt buffer and spring that has helped some people. I just got one and will report on it shortly.

[320pf]

Originally Posted by ReAX222

Going back to my notes, I built 10 rounds (I only shot 5 of them) 220gr Sierra Match kings, 10.0grs of 2400. OAL 2.260" built in February and it was cold (probably in the 50-60 degree range.) When I was shooting it was roughly mid 90s and very humid.

The upper was used and should have just over 100 rounds through it. I did drop some rem oil in the lower and I used my FP10 grease on the upper.

You might want to try a slower powder. I suggest that you start with AA#9. I have an upper (0.073" gas port in the pistol position) that does not shoot sub-sonic 2400 loads very well but does fine with AA#9. If that does not work try H110/W296 (These powders are basically the same, however, I think that W296 may be just a bit slower).


ReAX222,

The next slowest powers are H4227 which has been discontinued and replaced with IMR4227 (http://www.quarterbore.net/forums/showthread.php?t=2013) and AA1680

Here is a URL with several sub-sonic loads listed.

http://www.quarterbore.com/300whisper/subsonic.html

The loads listed for AA#5 and AA#7 will not work in an AR. These powders are way too fast.


320pf

[kdiver58]

ReAX222

Short stroking is a common problem. I can get almost any powder to cycle but getting the bolt to lock back was the biggest problem. I'm sold on AA-1680 for my sub sonic loads. If you are going to shoot both super-sonic and sub sonic don't get an Armforte adjustable gas tube they are junk. Get an adjustable gas block. IMHO

I'm amazed at how many of us are doing the same things. I've also switched to Mobile-1 AR's like to be wet and Mobil-1 handles the heat really good. Search my handle 320pf and interceptor's and you will find ton's of reloading data and a few videos.

What I an truly stunned about is that you were able to get a bullet that long into your upper. Mine was jamming into the lands at that length.
Did you have it reamed ??

Have fun and don't pull too much hair out ...