Strange Day Good Day

[bruce moulds]

doug,
I think you raise a very valid question.
I have used audette's ladder tests with fclass rifles for many years very successfully.
barrels are similar profile and length to my bpcr barrels, being 30 to 32" long, and 1" at the muzzle.
actions are trued and sleeved Remington and nesika bay. and of course barrels are free floated with tight necked chambers.
these guns will shoot most loads not too bad once a favoured seating depth is found.
ladders are done at 500 meters to spread out the shots on the paper.
as the charge increases in 0.3 gn intervals, the bullets go up the paper 'till a node appears, then start climbing again until the next node, and so on.
there are often 3 nodes in an acceptable velocity range, so you pick the widest one (most shots) all else being equal.
these ladders repeat.
no doubt a bpcr will behave similarly.
recent ammunition testing at 990 yards with a 40/72 showed groups going up the target with 1 gn powder increases peaking at 84 gns, then at 85 gns the groups started going downwards again. could not get more powder in the case so stopped there.
84 gns shot the best vert anyway so the load was decided.
this does suggest nodal activity, but other factors could have come into play.
no barometer readings were taken, so relative air pressure is unknown between groups.
sir henry halford makes mention of this, and the old time creedmoor shooters had a barometer on the range and knew what to do when pressure went up or down.
the powder compression was different to maintain the same coal. no chronograph that day to test muzzle velocity.
the fclass rifles are shot off a rest so shot to shot hold is virtually the same and a 32x scope with a target optimized for the dot is used.
hold and aim are good and consistent as is trigger letoff with jewell 2 oz triggers. also very quick lock time.
the bpcr is resting on the barrel, has iron sights, is lighter than the fclass rifle, has more barrel time, has a basic trigger system, has more recoil, and probably several other issues that give it a disadvantage.
however a similar result can possibly be achieved by shooting 10 shot groups rather than a single shot per load.
with the fclass rifle, you can have confidence to adjust the sight based on 1 shot.
with the bpcr you need probably 3 shots to make an accurate adjustment with confidence.
this reflects the relative accuracy of both systems.
a ladder test using different targets for each load and 10 shots per load would seem the best for bpcr.
10 shots is also a statistical number for group size.
range would need to be min 200 yds, pref 300, to see elevation differences of centres of groups.
aiming and shooting conditions need to be good for any ladder test to be meaningful.
please keep us informed with your most interesting journey,
keep safe,
bruce.