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Weight Sort Test; 30 XCBs of #2 Alloy
In previous posts I posted the graphed results of weight sorting a recently cast batch of 30 XCBs (NOE 310-165-FN 4 cavity aluminum mould). They were cast of Lyman #2 alloy and were WQ’d out of the mould. These were loaded in the 30×60 XCB cartridge with the standard HV load of 53 gr AA4350. That give 2900 fps out of the test rifle; a 31” Broughten Palma contoured barrel with a 16” twist on a BRNO VZ24 Mauser action. The rifle has a Leupold 6.5×20 target scope on it. This rifle was not made for BR shooting. It was made for HV cast bullet shooting to determine how fast a ternary cast bullet could be pushed while maintaining 2 moa accuracy (10 shot groups) linearly to 300+ yards. That goal was achieved. The rifle with weight sorted select 30 XCB bullets will hold 1 to 1 ½ moa accuracy (10 shot groups) to a tested 400 yards (so far).
Let’s keep in mind before we post I shoulda, coulda, woulda tested this many or that many of this or that using different 5 or 10 shot tests of each, etc. that in this batch of 542 cast XCBs there were just only so many of some weights. The number of each weight is on the previously posted graph and listed in the post. The number of some weights, particularly the lower weights, was finite. There were only so many to test….period. Thus I made some judgments on how many each would be a “group”. I strived for 10 shot groups but that was not possible with some weights.
I use the Lyman lino/lead/tin formula to mix #2 alloy. Since I mix my own #2 alloy I’ve found over casting and weight sorting 5,000+ of the 30 XCBs that different batches of #2 alloy usually produce slightly different weights of bullets. In this test I had used a different source of linotype (a pig bar) from the previous batch made with type. The result is that the bullets in this test weighed and average of 1.5 gr less than the previous batch’s 30 XCBs. There was little difference iif any in accuracy or velocity with the slightly lighter weight new XCBs. The previously used weight sorted select XCBs weighed 164 gr fully dressed while the new ones weighed 162.5 gr.
The test was conducted yesterday at a range of 100 yards. Nine test groups were fired plus a sighter target. The barrel was allowed to completely cool and was cleaned between every 3 test groups. One fouler was shot and then the subsequent shots would “go to group” centered on the CBA target. The “foulers were all shot with the heaviest weight sorted select bullets (157.9 gr.) and since it was obviously zeroed no adjustments were made throughout the test to elevation or windage. Each test group was shot with that zero aiming at the center “X” dot.
The fouler target;