#11 Postby williada » Thu Aug 20, 2015 12:19 am
Adam, did someone oil your primers? If its not a crook batch, pin protrusion check time. Max .006”. Then check spring pressure for minimum of 24 lb max 28 lb.
From what I am hearing, there is a change in the laminar flow of air densities induced by mound height at Belmont with sections of the range that funnel the laminar flows. That is, on the tops of mounds the air is compressed and meets a laminar flow of less dense air. You need gear to punch through this, not in terms of BC but in terms of velocity or a projectile of greater radius generating more torque with preference to tangent ogive or hybrid rather than a VLD that gets dizzy trying to re-orient itself with wind direction or clashing laminar flows. The crosswind condition does not upset things so much.
But elevation problems would be compounded by frontal or rear winds which always vary elevation at longer ranges as does changing cloud cover in terms of lights up sights up; and in warmer conditions creating a few thermals which die when there is cloud cover even in the absence of mirage? This is not the same as Adam’s problem. Such a combination of conditions can mean the person next to you can be in clear weather and you can be struggling with three or four factors influencing the game whether its a funnel effect or a thermal effect.
There are a few things shooters should be aware of. There may be only 30-40fps in extra velocity necessary to punch through the different laminar flow densities leaving bullet shape out of the equation. So those that tuned in colder weather could be right one range, and dead the next, depending on conditions if they are a in a cross wind or a frontal or rear wind. If its a rear wind its like surfing a wave. You have to manage a larger group and going for supercentres can strand you.
Similarly, if you used a lower node for accuracy while tuning in warmer conditions, it might not be enough either. The 7mm nodal ranges maybe seen as 2825-2850 fps for lower, 2925-2950 fps middle and 3025-3050 fps as some have documented. I know some run at much lower velocities. Each may be tight as hell for different shooters but ask yourself is your tune going to match range conditions. Just sometimes a weaker tune (bigger group with higher velocity) will score more highly if the conditions suit. BC won’t count as much, but re-iterating shape, mass, radial diameter does.
If you have ever done short range horizontal testing, you will also notice your zero move with velocity variables. So there can be an element of lateral and trying to read a condition becomes a little harder if you are using a lower node. So its best to shoot on the condition if you can, that is giving you a hit, that's where local knowledge comes in.
Looking at the equipment list, the SAUMS did well, but just maybe they had the slight velocity edge. It does not have to be much sometimes. Those 284 chamberings using the middle node may have been better off than those on an accurate low one. The only other conclusion I can reach, is that some were more fortunate with the draw and conditions and position on the mound. But it takes a skilled shooter to recognise and make the best of good luck.
While a less than solid base on spongy grass will effect group, I feel shooters had adequate warning of this issue at Belmont. The other problem is separating out a crook barrel. If your barrel was not fouling before you left why would you expect it to suddenly foul in a competitionon if your cleaning procedures have not changed? Its not like we use sealant, as old fullbore shooters used in the past. A fouling pattern tends to keep creeping you out the top and then back to normal. Bedding issues or loose fittings tend to chuck in real fliers, not the odd flier once at a range which may be the result of a dud round.
There are two additional points I would make. Do your load development in a cross wind, preferably from the right, not a headwind and North or South direction. This minimises lift factors and avoids perils of for or aft distortion of groups. It allows for an accurate zero. Secondly if you know that headwinds or tailwinds are going to be a factor on high mounds etc., sure run with a high BC if you can, but it is not the strength of the wind that will tip you out in these conditions, it is the responsiveness of the bullet to changing laminar flows. Select the right bullet. It may pay you to use a lighter bullet to punch through the turbulence with a higher velocity as another alternative if your high BC bullet cannot find a suitable higher node for group size. Its horses for courses.
David.
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