I've been watching the cold bore shot on some of my rifles. On one of them, it is very consistent. First cold shot is .75 to .5 moa low, then the point of impact rises, group holds well, then after fouling increases, point of impact rises again.
This isn't really a problem, because it is predictable. However, I heard one of the claims of HBN is that it has the possible advantage of having the cold bore shot shooting with the rest of the group.
I am curious and I'm going to give it a shot. I'm going to track the velocity of the rounds, find out when I get the velocity drop (indicating reduced pressure, therefore indicating reduced friction), develop a good load for the coated barrel, and after that happens I'm going to see about cold bore shots vs groups. Since I want to start with a cold bore and I'm waiting on materials yet, this project is going to take a while.
I thought I would post this in case any one else here has already done this and or is curious about how it might turn out.
If the load is properly developed, the cold bore shot will stay with the rest of the group... Using my OCW system of development, you can get your rifles to shoot like this--without any special chemicals or gizmos...
Then follow up with seating depth adjustments to fine tune the load. Adjusting seating depth AFTER you've identified the OCW is the icing on the cake (and reason number one why I don't use or recommend bullets that are seating depth sensitive)...
Lastly... don't inflict death-by-unga-bunga on your barrel when it comes time to clean... a couple passes with a good solvent... maybe soak the bore in Hoppes number 9 afterward... and it's more than clean enough. Look up Todd Hodnett's video on this on youtube... that's how I've been doing it for years, and it works.
Pons, Personally, I use WS2 for prefouling but HBN might work well.
If you take your barrels to CLEAN, which is more than a couple patches of Hoppes, there is typically a need for shooting to foul the bore. If you leave oil in the bore, it takes 5-8 shots to burn out & reach stable fouling. Also, some guns simply will not cold bore shoot with warm bore groups.
I had a Tubb2000 that would cold bore shoot, or hot bore shoot no problem, but from cold to hot bore there was a full 1/4moa of POI shift(often bigger than my grouping).
I solved the pre-fouling issue with all my guns by cleaning bores completely, drying them, and then dry burnishing with tungsten(WS2). My bullets are also coated.
With this, my first shot fits within a typical five shot group from cold, -for guns capable.
I can put my guns in the safe dry and know when I pull one, and drop it in the dirt on a bipod, the first shot IS good.
roy- i have also noticed extremes with ES and SD numbers on my most accurate load. i achieved the load by using ladder testing and therefore got the only load the i've been able to get to shoot sub 1/2 MOA consistently (.38 moa)