reamer difference
To look at two fireformed cases it is really hard to tell. However the reamer I started with has a very sharp break to the neck, while the ones for the AR are more of a radius on the shoulder, I talked with Lee Mosher the maker of the AR while I was trying to figure this out. He wanted me to send the upper back so he could diagnose the problem I was having feeding.
I was trying to use previously fireformed cases from my boltgun in the AR. The cases were not fully chambering. I started over with fresh fireforming and then reloaded cases fired out of the AR and voilla, problem fixed. The 3550 I posted was fireforming straight 223 cases. I use 2520 AA powder are recommended by Lee Mosher and I would tell you straight up that is not a powder I would of tried to start with, but it works really good in the AR. However lots of difference from lot to lot in AA powder. I used to be made in Communist block country but now is made in China or Israel, I think. I would have to look at a jug to see.
Lee really likes to use 26" barrels for max velocity, but I prefer shorter barrels, I can stand 100-150 less fps for ease of handling. Who can tell much difference when you get above 3500 until you get to 4000 fps.
Lee does considerable test firing before each upper leaves his hands and he knows they will shoot very tight groups. Quality, Quality, Quality.......I would like to try the tac 20 he builds but can't see how I can improve much over what I have right now.
joeinnm