Hi All, I am shooting a Compass lake Ar-15 with a Krieger 1-7.7 twist barrel for high power matches. I am planning on shooting leg matches next year. Currently I shoot 77 gr. Lapua Scenars with Lake City brass with VV N135 and CCI Br-4 primers for practice at 100 yards. For the 600 yard leg match, I expect to use Lapua Match Brass. Here is my problem. With the Lake City brass I can seat the bullet to achieve an OAL of 2.460" for the single load events. This load is highly accurate out of my AR- however when I try to replicate the same OAL on Lapua brass (this is first loading), a 2.460 OAL will not chamber and I have a stuck round issue. I would have to seat the bullet around 2.360" with the Lapua brass for it to chamber properly. I have noticed that the neck diameter of LC brass is approx .245-.246" while Lapua is a little thicker, .249-.250". I am at a loss, why would the LC brass chamber with a longer OAL than Lapua. My initial theory is the case neck thickness, but that shouldn't matter in this situation right? Anyone have any thoughts or insight into this? Also, would it be recommended to turn the neck for the AR? I would imagine a Compass Lake would have a tight chamber as well even though it is a semi-auto. Thank you in advance for any info you can provide.