dstoenner
Silver $$ Contributor
I don't remember how long ago I bought my Sinclair concentricity gauge, maybe 10 years. I have used it to diagnose lots of setup issues and as a matter of trying to take the best ammo to the line, I load in batches and then sort by concentricity.
I know, I know, that a lot of you on this forum think it is useless. What happened today is a case to consider that it is a good idea.
I was loading up 100 Lapua 223 cases. I as going to split the box into 50 using Berger 52 Target and the other 50 Berger 55 Target. The cases have been fired 3 times. This is the 4th loading. The 100 cases were pulled out of the box at random and placed in the loading blocks. Because I was close to the needed 55 seating setup, I did those 50 first. These are for a bolt gun so they were loaded seated at 2.310. The runout density was pretty normal.
19 = 1mil
29 = 2mil
1 = 3mil
1 = 4mil.
So then I loaded up the second 50 with 52's, also loaded out to a max seating depth of 2.275. Took them to the office and started sorting. First one measured was a little over 5mils. WHAT!!! but I kept on. This group was all over. When I was done the sorting looked like:
12 = 1mil
5 = 2mils
18 = 3mils
4 = 4mils
6 = 5mils
4 > 5mils (1 was 8)
This is completely abnormal, especially for Berger bullets in Lapua cases. What I measured is not at all what I would expect that the 4th loading would generate for a percentage of 1 and 2 mil runout. But this group was the worst set of 50 I think I have loaded with a known good setup. Ever.
I did some experiments back when I first got my concentricity gauge and did some seating depth vs runout on the same bullet and case. I started really long with less than 1 caliber of bearing surface in the neck. As I kept increasing the seating depth by .010 inches the runout on that bullet case kept getting better till when I had the full bearing surface in the neck it was the best.
So I thought why not. These 52's shoot well in my AR15's loaded at mag length. Lets just reseat them .020 deeper for a COAL of 2.255. I took the tray down as sorted and then started at position 1 and kept reseating till I got to 50. Took them back to my office and resorted the batch. Completely different numbers:
15 = 1mil
25 = 2mils
5 = 3mils
3 = 4mils
3 = 5 mils
Still not as great an outcome as hoped for BUT this batch was salvaged. Had I just taken the 50 to the range and they shot whacko I probably would have never known what was wrong. But by doing the extra step up front I saved myself a lot of anguish. Even if this batch doesn't shoot great, I know about what is in it and I can be on the lookout.
SO that is why I do it. Everyone of us makes mistakes and if we aren't checking ourselves the best we can we are just fooling ourselves.
David
I know, I know, that a lot of you on this forum think it is useless. What happened today is a case to consider that it is a good idea.
I was loading up 100 Lapua 223 cases. I as going to split the box into 50 using Berger 52 Target and the other 50 Berger 55 Target. The cases have been fired 3 times. This is the 4th loading. The 100 cases were pulled out of the box at random and placed in the loading blocks. Because I was close to the needed 55 seating setup, I did those 50 first. These are for a bolt gun so they were loaded seated at 2.310. The runout density was pretty normal.
19 = 1mil
29 = 2mil
1 = 3mil
1 = 4mil.
So then I loaded up the second 50 with 52's, also loaded out to a max seating depth of 2.275. Took them to the office and started sorting. First one measured was a little over 5mils. WHAT!!! but I kept on. This group was all over. When I was done the sorting looked like:
12 = 1mil
5 = 2mils
18 = 3mils
4 = 4mils
6 = 5mils
4 > 5mils (1 was 8)
This is completely abnormal, especially for Berger bullets in Lapua cases. What I measured is not at all what I would expect that the 4th loading would generate for a percentage of 1 and 2 mil runout. But this group was the worst set of 50 I think I have loaded with a known good setup. Ever.
I did some experiments back when I first got my concentricity gauge and did some seating depth vs runout on the same bullet and case. I started really long with less than 1 caliber of bearing surface in the neck. As I kept increasing the seating depth by .010 inches the runout on that bullet case kept getting better till when I had the full bearing surface in the neck it was the best.
So I thought why not. These 52's shoot well in my AR15's loaded at mag length. Lets just reseat them .020 deeper for a COAL of 2.255. I took the tray down as sorted and then started at position 1 and kept reseating till I got to 50. Took them back to my office and resorted the batch. Completely different numbers:
15 = 1mil
25 = 2mils
5 = 3mils
3 = 4mils
3 = 5 mils
Still not as great an outcome as hoped for BUT this batch was salvaged. Had I just taken the 50 to the range and they shot whacko I probably would have never known what was wrong. But by doing the extra step up front I saved myself a lot of anguish. Even if this batch doesn't shoot great, I know about what is in it and I can be on the lookout.
SO that is why I do it. Everyone of us makes mistakes and if we aren't checking ourselves the best we can we are just fooling ourselves.
David
