PHOENIX PHIL
AH ambassador
I'm not sure everyone fully understands what a project you can be taking on when using a double rifle.... I'm still not convinced it is my favorite thing. They are fun to own and shoot. But bolt guns are easy once you have one that feeds reliably. Dealing with one barrel is certainly much simpler. Exponentially so.
Phil is correct in that slight changes in speed, etc have major effects. Heck I mentioned that I'm not sure it's ok to shoot a double of the bench. Regulation will likely change by the way recoil is handled.
I remember shooting my first 505 Gibbs off sticks at 50 yards and having 600 grain bullets going at 1950 fps hitting 8" higher than 525 grain at 2300 fps. The hypothesis was that after ignition but prior to the bullet leaving the muzzle, the recoil rize of said muzzle was greater simply because the bullet was traveling slower down the barrel during recoil.
For me the mind games come into play when you start thinking about the cross section of regulation and accuracy. The two are most certainly related, but are not the same thing. It's easy to get into a spiral of thinking and head off into the weeds.
When it comes to doubles, we always look to see what the rifle was regulated too in regards to muzzle velocity. From there we presume this is the velocity we should be loading to when we attempt to develop another load.
So let's presume we head in that direction. Our brand new to us rifle was regulated to 2200fps m.v. using Horndady DGX bullets. Maybe we even know the powder is H4831 (choosing this just cause that seems to be the most popular in .470NE).
So armed with starting load data, we load up a bunch of our favorite bullet in from some low point to some high point in regards to powder charge. And off to the range we go.
One potential outcome that I believe I've seen myself is as follows. Working from low to high in our rounds, we initially see quite a large spread in the printing of the two rounds. As we increase the load, they start to come in also as expected. Now we're doing this making use of a chrono and taking good notes on the results.
At some point our charge is resulting in a muzzle velocity that matches up with what the rifle is regulated to, but the bullets are printing with a bit more spread than we want. As we continue up in charge that spread gets better, but we're also now at an appreciably higher velocity than what it was regulated too. This also may be at a point that we're satisfied but also could be that we know we could get a little bit closer with more charge.
One other potential outcome is that at some velocity we have achieve the best two bullet spread we can and then things get worse from there.
This is what I'm trying to get at in regards to the cross section of regulation an accuracy.
I think it is quite possible that one will have equal or better accuracy at different charge weights and therefore muzzle velocities with different bullets from that which the rifle was regulated to.
It may also be that you never attain the two bullet print that you're looking for with a particular bullet.
At this point it's easy to get caught up in the regulation game and start to think you need to have the rifle regulated again for your favorite bullet. Perhaps so, but then maybe you just need to develop the load custom to your rifle the same as one would do with their bolt actions. And then again, maybe it's time to give up on that bullet as ever being the best choice in regards to accuracy for your rifle.
Once again my thoughts running wild and not an expert opinion in the least. I'm still learning about these finicky guns. Please feel free to poke holes in my thought process if you wish, it's how we learn.
@AZDAVE, I'd appreciate your thoughts on this.
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