Wilson / Sinclair trimmer assembly with 6BR case in its holder
offer a custom sizer-die based on a fired case, but can’t guarantee they’ll be able to match the rifle chamber and also provide custom bullet seater-die sleeves and stems, the former also requiring a sized case to use as a pattern. My standard die gives very concentric results and the stem happily accepts all bullets I’ve tried to date, so I wouldn’t feel any need to go down this route.
Chamber Issues I mentioned there were two ‘problems’ or issues when I got my die set and started loading the cartridge. The second was entirely my fault in that I was lazy about setting the sizer-die up in the press and didn’t check what it was doing to the shoulder. Over many years handloading, I’ve usually found the ‘default setting’ that sees the shellholder and die body in hard contact taking up any press frame flex at full handle operation gives results that are close to ideal – the shoulder is set back but only marginally.
58 Target Shooter
Not so with either of my 6mm BR FL sizers or the Redding ‘body die’– set them up thus and the shoulder is pushed back a large amount creating excessive headspace. The giveaway with these initial loads was substantial case length growth on being fired, increasing by ten thou’ or more from Lapua’s out of the box 1.555 inches, to somewhere above 1.565 inches and getting on for 1.570 inches in some examples. The cartridge’s CIP and SAAMI maximum allowed case length is 1.560 inches, ‘trim-to’ 1.550 inches.
Such massive growth in a single firing indicated something badly wrong somewhere and checking the sized v fired case headspace lengths in a Stoney-Point/Hornady L-N-L gauge and comparator body on callipers provided the answer. Dies are now used screwed well back from contact with the shellholder to set the shoulder back a thou’, setting-up done in conjunction with the headspace gauge and also
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