Really. The standard pressure signs are to be ignored then? And what distance? I shot my tests at 200.Originally Posted by Randy Bohannon
EVEN IF I had worked the load up with a chrono it would have meant nothing other than at 3200 FPS with a 155gr bullet I was over the 3105 HME limit.
It would not have shown hard extractions, case head expansion (you can measure that with shooting shed's excellent gauges) bolth thrust signs, primer flattening, or accounted for temp senistivity or the ammo. With some brass (such as the .308 Lapua Palma) you will not see most of the usual pressure signs unless they are severe. Bolt thrust marks and head measurment is a good indicator.
It would not have known that for litigation reasons many load limits are over safe (but I do not suggest they are ever ignored), that the Lilja 3 groove barrel was designed for higher velocity and produced them with loads that would produce a lower velocity in barrels of the same length with more grooves. It would also have no idea about what powder was being used, COAL, compressed or not (which can often produce more consistant ES but with no real gain in velocity).
In fact, it was the use of the chrono that stopped me using a match winning load and down loading to the detriment of my results. The particular bullet needed to be pushed (Berger Hybrid 155), only later when speaking to a chap from Lilja did I realise the various factors that showed such good results were manifold and safe, but at least I then knew what was the norm.
The chrono will show you a number, it is what you do with it that counts, and this often leads to chronoitis. Barrels get burned out and constantly tested but not much gets achieved because the owner is never satisfied and destroys the barrel looking for the "Numeric" best and not looking at the actual results on paper. In many cases these tests are carried out well before the barrel is even shot in so the odd velocities may well be nothing to do with the load and all to do with minor copper build up.
My point? they can lead you down the garden path as well as being a help.
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