Tuning vertical
- Thread starter Rflshootr
- Start date
TomD
e publius unum
Actually either way with powder charge at .3 grain increments. Read below, written by Gene Beggs (I think).
Assuming a 6ppc with a LV contour 22 inches long shooting 68 grain bullets with N133 powder, the tuning nodes or "sweet spots" as some shooters call them, appear at 120 fps intervals. Or, expressed in terms of powder charge, 1.2 grain intervals. Most benchrest rifles behave in a similar fashion. You can prove this with your rifle by shooting several three shot groups beginning at 27 grains and increasing in .3 grain intervals up to a max of 30 grains. If the rifle is in tune and shooting dots at 27 grains, it will begin to show vertical at 27.3 grains and will be completely out of tune at 27.6 grains. It will come back together at 28.2 grains and will again be completely out of tune at 28.8, the last node appearing at 30 grains.
Once the rifle is in tune, make a note of the density altitude and charge weight. If DA increases by 500 feet, decrease the load by .3 grains and vice versa.
If DA goes up decrease the load; if DA decreases increase the load. The formula is .3 grains per 500 feet DA. Since temperature is the main reason for changes in DA you can accomplish the same thing by using only a thermometer. The ratio is .3 grains per five degrees F.
Assuming a 6ppc with a LV contour 22 inches long shooting 68 grain bullets with N133 powder, the tuning nodes or "sweet spots" as some shooters call them, appear at 120 fps intervals. Or, expressed in terms of powder charge, 1.2 grain intervals. Most benchrest rifles behave in a similar fashion. You can prove this with your rifle by shooting several three shot groups beginning at 27 grains and increasing in .3 grain intervals up to a max of 30 grains. If the rifle is in tune and shooting dots at 27 grains, it will begin to show vertical at 27.3 grains and will be completely out of tune at 27.6 grains. It will come back together at 28.2 grains and will again be completely out of tune at 28.8, the last node appearing at 30 grains.
Once the rifle is in tune, make a note of the density altitude and charge weight. If DA increases by 500 feet, decrease the load by .3 grains and vice versa.
If DA goes up decrease the load; if DA decreases increase the load. The formula is .3 grains per 500 feet DA. Since temperature is the main reason for changes in DA you can accomplish the same thing by using only a thermometer. The ratio is .3 grains per five degrees F.
B
BJS6
Guest
Lord knows I am no expert but based on my testing it seems to me that once you have a bullet that the barrel likes and a suitable powder the bulk of the tuning always has to be with the powder charge, then seating depth to fine tune.
I reckon if the load is off perfect tune by about 0.2 grains on the powder charge you can effect the same change in tune with seating depth alterations instead of powder. If the load would need a change of say 0.4 grains of powder to get in proper tune you will not tune the load with seating depth only, you will need to get the powder right first and then get the last bit out of the groups with the seating depth.
As Tom said, if you have vertical you are not likely more than about 0.6 grains off the right load. Talking 6PPC and N133 here. You can only go up in the charge if you are not already loading real hot. If you are loading say 29.0 and have 0.35 vertical I'd try 28.8 and 28.6 and also 29.2 and 29.4. See what you have and maybe fine tune the powder a tad more. Then alter the seating depth from there.
If altering the powder doesn't help it may be that the seating depth is miles off and you need to adjust that first, then the powder and then fine tune with small changes in seating.
It is all just trial and error with some logical method to keep track of what works and what doesn't. Observe the trends in what improves accuracy and what degrades it and use those trends as a guide on which way to keep altering powder or seating. Done while loading at the range it is usually pretty simple if the rifle shoots and the bullets suit the barrel, keeping it shooting in different conditions is where the fun starts.
Hope that is some use.
Bryce
I reckon if the load is off perfect tune by about 0.2 grains on the powder charge you can effect the same change in tune with seating depth alterations instead of powder. If the load would need a change of say 0.4 grains of powder to get in proper tune you will not tune the load with seating depth only, you will need to get the powder right first and then get the last bit out of the groups with the seating depth.
As Tom said, if you have vertical you are not likely more than about 0.6 grains off the right load. Talking 6PPC and N133 here. You can only go up in the charge if you are not already loading real hot. If you are loading say 29.0 and have 0.35 vertical I'd try 28.8 and 28.6 and also 29.2 and 29.4. See what you have and maybe fine tune the powder a tad more. Then alter the seating depth from there.
If altering the powder doesn't help it may be that the seating depth is miles off and you need to adjust that first, then the powder and then fine tune with small changes in seating.
It is all just trial and error with some logical method to keep track of what works and what doesn't. Observe the trends in what improves accuracy and what degrades it and use those trends as a guide on which way to keep altering powder or seating. Done while loading at the range it is usually pretty simple if the rifle shoots and the bullets suit the barrel, keeping it shooting in different conditions is where the fun starts.
Hope that is some use.
Bryce
N
nonliberal
Guest
It may or may not help, but I thought this was good info on the Vertical topic.
http://www.6mmbr.com/verticaltips.html
http://www.6mmbr.com/verticaltips.html