Have you ever loaded a round for shooting anything past 25 yards?
. . . of course. I usually shoot 100y.
The closer the bullet is to the lands the more pressure it will create. More pressure usually means faster velocities, however it is a moot amount. ie seating a bullet .020"-.050 deeper will not increase velocities 50 fps.
I could be wrong, I'm going to look into that one further, but as it is right now, I have quite a bit of Chrony and load data backing up my claim.
Last time I did the experiment :
223;80g A-Max;21g3031;
2.5" = 2440.8fps
2.45"=2495fps.
That's based on a 5 shot average.
I'm going to try it again tomorrow, I'm working up some loads with this new CFE223 powder I've been wanting to try.
Just made 5 rounds each, 23g@ 2.275" and 2.5" w/75g BTHP.
I'll let you know how that goes.
Seating depths will change accuracy but it depends more on the bullet and what the rifle likes. Some bullets like the Sierra SMK are very intolerant to jump. Some rifle/bullet combos may like the bullet jammed into the lands. While the same rifle will like another bullet of the same weight to have .040-.050 jump with the same load.
Pretty much what I was trying to sum up with: "A long OAL and a short jump does not always equate to better accuracy" as I got the impression that the OP believes that the longer the better. So, yeah, I agree entirely.
I do not believe that by loading hot, you can over spin a bullet provided you are using the proper weight bullet for the twist rate in your barrel and the proper powder. You will get to a point were you will not get any more velocity as unburnt powder will blow out the end of the barrel.
I was referring specifically to cases where someone would be using a much slower burning with a long OAL and by time they got the case filled to the point of consistent combustion they are pushing the bullet faster then they should be. Perhaps I could of been more specific, but I was jsut kind of hammering out some coles notes for the OP to think about.
Forget the self engineered load data. Finding the sweet spot with your loads is done at the range, not at a keyboard.
Can't argue with range results, but, being over a decade into the 21st century, we now have computer software that can accurately predict the performance of a round before we've even made it.
I know this for a fact for sure, and it does work. 30 mins at the keyboard can save me hours of range work, and I can get right to shooting groups.
Of course you can't have one without the other, there is still quite of bit of range work involved, and you pretty much have to kick it oldschool starting from scratch with a new to you rifle.
After playing around with different loads in the same rifle, you can compile quite a bit of data, and once you've found the sweet spot for one load, you can use that data and compute where the sweet spot might be for another load with a different powder or bullet. It can greatly speed up the "work up" processes as you can skip the graduated loading and go right to fine tuning.
For instance, I have chony data that tells me where the sweet spot is for the 80g A-Max bullet in my rifle. And since determined that 2.5" was my ideal OAL via that experiment I mentioned.
But I wanted to optimize my powder burn.
So, at the keyboard, I was able to determine that IMR 3031 was the best powder for my application, and that 21g of said powder would put me in the sweet area with something like 100% case fill and 99.9x% powder burn.
I loaded it up and sure enough, I shot a 0.203 and 0.503.
I chrony'd the load and saw that I was jsut a few FPS short of where I wanted to be. So I fine tuned the load to 21.3g and sure enough, I shot a 0.171 and 0.274. I was able to tighten it up and get more consistency with just 2 attempts.
This is what I'm talking about, to answer the OP's follow up question.
My gun is a Tikka T3 lite, 223 w/Minox 4-20x50. And these groups were shot prone with a bi-pod. I'd probably get a one hole if I did benchrest.
