Blast a 55gn bullet out of a 1-8 twist barrel at 3600 fps and it rotates at 324,000 rpm compared to just over 185,000 rpm in one with a 1-14 rate. Let’s put the integrity issue to bed now – out of 170 groups fired with 55-87gn varmint bullets - 850 or so shots - I didn’t suffer a single failure and that was in a barrel with a considerably eroded throat. That’s not to say it can’t happen – a rough, badly fouled bore and temperatures higher than seen at Diggle might very well induce bullet failure, or it might happen at greater distances beyond the 100 yards I used for testing.
So far as COAL is concerned, the throat was too long in my chamber to have any 55-70gn bullet ogive just off the rifling whilst seating even a small part of the bullet-shank in the case-neck. I simply seated these models with an eighth to tenth of an inch of the parallel shank or bearing surface into the neck, before looking for a powder and charge weight combination that would group well despite a 0.1-0.2 inch jump into the rifling leade.
These bullets are either flat-base or if nominally boat- tails, have such a tiny and short tapered rear section that it performs no function other than easing the bullet’s entry into the case-mouth during the seating operation. This helps out here as nearly all of the
THE HANDLOADING BENCH 6mm NORMA BENCH REST (Conclusion) by Laurie Holland
lower bullet body is available to be gripped by the case. Those 75-87gn models tried are noticeably longer and could just be seated, albeit shallowly to reach the leade. This would put their bases on - more usually a little above - the bottom of the case-neck, whilst providing my usual 0.015 inch jump into the rifling (or seated into the rifling if so desired with the odd secant ogive model).
When using mid burning rate powders like Viht N140/ N150, Hodgdon H4895 and VarGet whose top loads run above 30gn, I often had a desirable ‘no airspace’ set-up with the case capacity fully utilised by the charge almost to, or right up against, the bullet base with these bullets. This was with the chamber as cut by Norman Clark’s reamer of course. If you’ve specified a really long throat to suit the longest 105gn VLD on the market or a 115gn design seated at the optimal position in the case, all varmint bullets would likely make a full quarter inch or even longer jump.
What about powders for these light bullets? Faster burners – Alliant Reloder 10x, Accurate 2015 and 2230, Hodgdon H322 and Benchmark, Viht N133/N135 seem
There is a huge choice of 6mm varmint and deer bullets, of which this is a tiny part
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