I'm seating .264" 120 gr. Barnes Match Burners over 27.5 gr. of H335 with a Redding seater on an RCBS single stage press. Without adjusting my seater, I seated the first one and measured it at 2.250" OAL. Barne's published data shows 2.220" so I continued to seat bullets. I found they varied by as much as +/- ten thou.
The Barnes data shows a maximum load of 28 grains and indicates it will be a compressed load. Figuring that I am compressing the powder, I backed off the seater by ten thou and seated all the bullets. Then I adjusted it in to seat a second time at 2.250". I'm doing 100. So I finished the second pass with the seater.
I attached my Sinclair comparator to the calipers and zeroed it on the first one. I found about half were that length +/- one thou. Another 40 or so were as much as 7 thou shorter. About 10 were about 5 thou longer. I sorted them into like OAL and packed them in MTM cases.
I have another 600 to load. What's going wrong?
I suspect it's the compressed powder that's pushing back. I have 8 pounds of this one and I'm not about to find another anytime soon. I can a seat a little longer. I'm limited by magazine length rather than throat. Even so, Barnes shows their 140 gr. Match Burner fitting over 27.6 gr. of H335 in 2.240" OAL. Again, I'm seating the shorter 120 gr. Match Burner over 27.5 gr. of H335 at around 2.250"
