I fired a sweet AR pistol today. But were having problems with chambering. When using 5.56 no problems at all. When using .223 black hills we spent more time trying to get the bolt back, than shooting. Tried different mags. Any ideas??  FYI the bolt doesn't go all the way forward on the .223. When it did go forward and fire, then it was a failure to extract....

ok, so this is what someone just told me... Doesn't seem right. He said that it happens because the BCG is an M16 and not an ar-15. That m16 is specific to 5.56. that doesn't seem to make sense to me since the diameter is the same. When I mention that, he got real quiet.... and had no response.

http://en.wikipedia.org/wiki/5.56x45mm_NATO#Cartridge_dimensions





"The 5.56 mm NATO and .223 Remington
cartridges and chamberings are similar but not identical. Military
cases are generally made from thicker brass than commercial cases; this
reduces the powder capacity (an important consideration for handloaders^{[url=http://en.wikipedia.org/wiki/5.56x45mm_NATO#cite_note-5][6][/url]}), and the NATO specification allows a higher chamber pressure....."


––––––––––-





http://en.wikipedia.org/wiki/.223_Remington

223 Remington versus 5.56 mm NATO

"While the 5.56mm NATO and .223 Remington cartridges and chamberings are very similar, they are not identical...."

––––––––––––––––––





I'm sure you will figure it out.  





 

Thanx for the input.. I talked to a buddy today and he said he had the same problem on a build he did a few years ago. It turned out to be a "timing issue".  That if I change the buffer assembly to a standard CAR length, that will fix it. He stated that using the 223 was providing too much gas and the buffer wasn't cycling properly. His thought that was, a pistol buffer was cycling TOO fast and that was keeping the BCG from properly chambering the round. Sounds right.......I'll give it a try, if that don't work I guess I'll just shoot 5.56...........................OH yeah, I purchased it, and shot it more today. 5.56 functions flawlessly  through it.  Thanx SILENT_PRODIGY. great build and It will be a great tool for me.

The 5.56 produces much more pressure than .223.  If your gun is cycling with 5.56 and not .223, it might need 5.56 pressure to cycle your gun.  It sounds like to me your gas port is too small or not lined up properly with the gas block.

Correct, but there is no difference in bolts.

Thanx for the tip, I'll check that. I'm hoping to get this thing firing both. I'm gonna change the buffer assembly, cause I've heard that using a CAR assembly will cut down on any cycling problems. Maybe between the 2 this thing will be bullet proof.