I'm no expert in this matter, but I have had discussions with friends on this subject. Some have really paid a lot of attention to this measurement. As far as me, I never did. I just went with the measurement in the book. I guess if I was a benchrest shooter, I would worry about it. I just didn't see any really difference in the measurements.
No the longest is not always best. What I prefer to do when possible is to seat my bullets so the base is about at the bottom of the case neck where it starts to flare to the shoulder. I then determine what load is most accurate with this seating depth and if I find a load that meets my accuracy requirements at that seating depth I don't mess around with it more. Only when that doesn't give me adequate accuracy to meet my needs to I mess around more with seating depth.
For big game hunting loads I pretty much never mess around with it. For varmint/target loads in really accurate rifles I'll vary it some in an effort to reach 1/2 MOA accuracy if needed but when I reach 1/2" to to 3/4" groups for five shots at 100 yards most of the time then I will not usually put more effort into it than that. I've really never been one to just keep on working on load development to get the Nth degree of accuracy from my load or rifle. I know what level of accuracy satisfies me and when I reach it I stop load development and just use that.
There is no simple answer - yes it is best or no it is not best. Gray Beard covered it pretty well. Personally - in Revolver loads I stick with the recommended OAL as much as possible. In hunting loads I use the same criteria that Gray Beard does. In a hunting load, accuracy is not the only concern; reliable functioning is very important too. Get cartridges too long and they hang up in the action. Too short and you are cutting down on the velocities possible with it. In the target/varmint guns I try to start at the lands, if possible. Again this may be dictated by the functioning of the action or the throat maybe too long to seat the bullet in to the lands. If I can not start at the lands, then I back off as little as possible, and still cycle through the gun and enough of the bullet in the neck. But generally make the cartridge as long as I dare. I pick a likely powder and bullet. I vary the powder charges starting with the lowest recommended and slowly work my way up to maximum. Knowing that maximum in the book may be too high if I am into the lands already. I then vary the seating depth if I do not get satisfactory results. What is satisfactory to one is not to another. I used to think I had to get sub 1/2 MOA with five shots on every varmint gun I own. When I had one varmint gun that was possible, I do not have the time to work up a great load for every gun I own. Like Gray Beard, If I can get it into 3/4" constantly I am good. A bench rest shooter is concerned about getting every ounce of accuracy they can out of one gun. They spend the time to develop the perfect load. I just do not have the time. I have several "varmint" guns and it takes considerable time to work up the perfect load. I like doing that, it is kind of therapeutic to me, just do not have the time to do it anymore, there are way too many variables to work out.
I agree, GB covered it pretty well. I have loaded ammo from .150 off th lands to Jammed into the lands. Every rifle seem to be different in what it prefers. I have had a few that it just didn`t seem to matter where the bullet was seated and others that like the bullets jammed into the rifling's and even some that liked a long jump. Most of the time I find that I get better accuracy with ammo that is longer than SAMMI spec, but not always. For my AR I loaded the first test ammo as long as I could and still have it feed through the magazine. The first 5 shots measured .700 center to center so I never tried any other loads as this rifle is for hunting coyotes behind dogs and most shooting will be off handed at running targets and that`s a tighter group than I will be able to hold by far.
I 've always loaded everything as long as I can but stay off the lands .010". Sometimes the magazine limits the length, sometimes the bullet and sometimes its the chamber. I 've never had that be a problem and I believe in most instances it is the most accurate method. My short answer would be ...yes.
I usually load .010 off if possible. I picked up a thread, this sight another what ever, where this shooter shot some very good groups with a 100 g Hornady in a 7mm mag. I tried it and the best group I have ever had out of that rifle, -1"@100. To make sure the COL was safe a load the bullet it had a .26" jump.
I use an OAL gauge to determine the length to stay .020 - .040 off the lands. Usually in a bolt gun, this length won't feed from the magazine, so I shorten it until it feeds reliably. OAL seems to make the most difference in small bores, but it could just be me. It is worth checking. Sometimes a few thousands can make a big difference in accuracy. If you're having trouble wringing a rifle out, check it.
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