help me make sense of this?

[Parabuteo]

A chronograph is the next best thing to a pressure lab in these circumstances.

Really. The standard pressure signs are to be ignored then? And what distance? I shot my tests at 200.

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.

[Randy Bohannon]

Really. The standard pressure signs are to be ignored then? And what distance? I shot my tests at 200.

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.

No, the standard pressure signs are not to be ignored, notice that in case they are not present however.

You've illustrated that above why a chrono is more useful than looking at primers.

Army medic seems able to handle complexity and data points, therefore the more data points he has the better.

Some of us, at least, can cope with numbers without being led astray somehow...

[Parabuteo]

No, the standard pressure signs are not to be ignored, notice that in case they are not present however.

You've illustrated that above why a chrono is more useful than looking at primers.

Army medic seems able to handle complexity and data points, therefore the more data points he has the better.

Some of us, at least, can cope with numbers without being led astray somehow...

If you had the slightest idea of my background you would not have said that, still a fool and its platform. Get all the stats you want. Did it, found it had no real bearing on actual performance and stopped worrying about it.

Those still burning out barrels (to achieve meaningfull stats accross pressure altitude and temp bands) and achieveing sweet FA are still about, I burn mine out with use and practical application.

Stop clutching at straws. Looking at primers is simply a small tell tale as to whether you are overpessuring your setup when an acceptable (repeatable) result is seen. You can also measure your case head. It has no bearing beyond that, but if it suits your attempts to prove a point, crack on.

You will get some (Often quite large) changes in velocity across even the most carefully prepared loads but these are (usually) statisticaly part of the picture and less often down to the firer than you may think. Many will focus on the 4 rounds in the tight group and ignore the flier, but the flier (if you shot correctly to make the stats mean something) is part of the picture and will invariably show itself agaion in some patern.

A lot of extensive work has been done by the F/BR and tactical fraternity into barrel length/profile and effects of various loads on harmonics, and the bottom line usually comes down to down range performance. There will always be oddities, and the problems begin when you keep chasing these oddities (In varying conditions) trying to re-create the outcome.

You know yourself you can shoot 2 totally different groups with the same setup, on the same day, even off of a fixed rifle, so how does knowing the stats explain that? You have seen it on paper? Moreover, a lot of the chronos that require soem sort of attachment will affect the harmonics, so the true downrange result is lost. What's the point? What was your neck tension? Are all neck tensions the same? Has the brass all work hardened similarly? Do the cases have the same capacity? Do they all expand and spring back as the others do? Was the seating depth 100% consistent? Has copper built up during the test string? Are the bullets bearing surface all the same? With an attached chrono or not, which of these possible causes explains the very limited stats presented? Were You were more accurate in the load process with some rounds than others? Its means nothing if you have interfered with the harmonics so the group wont be a true representation.

I lose count of the number of people that support rifles to the Nth degree for testing, then wonder why without the bipod, without the rear bag, with a different hold and a sling, the thing shoots worse (or in the case of my old M67 better). Mine are all tested as they will be competed with for good reason.

I agree that the current crop of radar chronos have their uses, but so far for me, they have raised more questions about loads that are giving throughly respectable down range results, than they have provided answers.

Then we go onto the current habit of testing in electronic targets....How well calibrated are they? Do they miss the odd round? A recent bumch of very sheepish competitors that blew all the longer phases of a comp can attest to what happens when you TRUST tech to do what should be done manually

Accurate setups have been about for years without the need for over tech, trust your judgement